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May
3
2

Here be Dragons

By Kevin Orrman-Rossiter | Filed in Science communication, Science policy, Space Science

On May 11, a Dragon will mate with the International Space station.  Rather than some mythical creature, this Dragon is of human artifice.  The Dragon’s rendezvous and berthing with the International Space Station presages a new chapter in human exploration of space.

The significance of this event is Dragon is a reusable spacecraft, developed, and built by the American company Space Exploration Technologies, SpaceX, as it is more commonly known.  Established in 2002, SpaceX has developed a new family of launch and cargo and crew capsules from the ground up.

The commercial race to space

NASA has now “set it sights on exploring once again beyond low earth orbit.”  This gives the opportunity for private industry to take on routine access to space and resupply of the International Space Station.  From the U.S. perspective the first phase of this strategy is known as Commercial Orbital Transportation Services.  This program, announced on January 18, 2006, is to fund and co-ordinate the delivery of cargo and crew to the International Space Station.

This photograph, taken by one of the Expedition 30 crewmembers aboard the International Space Station from approximately 384km above the southeastern Tasman Sea, is believed to be the one-millionth still image recorded by space station crews. The view, focuses on an area just west of the south end of South Island, New Zealand and was taken about 3:19 a.m. New Zealand time, March 7, 2012. A Russian Soyuz and a Russian Progress vehicle are seen center and right in the foreground, respectively. Photo credit NASA.

After a series of competitions and capability demonstrations in 2006 and 2008 two companies were chosen by NASA to receive funding via this program.  Initially in 2006 SpaceX and Rocketplane Kistler were awarded agreements through to 2010.  However the agreement with Rocketplane Kistler was terminated in 2007 when it had failed to raise sufficient private equity funds.  In a second round of competition Orbital Sciences Corporation was awarded, in 2008, the second group of agreements.

Orbital are no new comers to the space arena.  It is an American company, which specializes in the manufacturing and launch of satellites.  Its Launch Systems Group is heavily involved with missile defence launch systems.  Orbital Sciences since inception, in 1982, has built 569 launch vehicles with 82 more to be delivered by 2015.  This includes 174 satellites have been built by the company since 1982 with 24 more to be delivered by 2015.  With the tag “Innovation you can count on” Orbital present a solid commercial face for routine access and resupply of the International Space Station.

SpaceX on the other hand present a more entrepreneurial face to the world.  This is due, no doubt, to the strong influence of its founder Elon Musk.  Musk has notably made his mark with the creation and sale of the companies Zip2 and PayPal.  His current ventures include the listed Tesla Motors and un-listed SolarCity.  His ambition for SpaceX is obvious in the type of development program they are undertaking.

SpaceX has the Falcon family of launch vehicles and their Dragon cargo and crew capsule.  SpaceX is “based on the philosophy that simplicity, low cost and reliability go hand in hand.”  The sales blurb on their website emphasizes “we recognize that nothing is more important than getting our customer’s satellite or other spacecraft safely to its intended destination.”  Make no mistake this is a commercial enterprise in that “can do” American entrepreneurial model.

In case you were wondering, for a mere US$10.9M a Falcon 1 could deliver your 1010kg payload into a 185km circular low Earth orbit.  Alternatively US$54.0M gets you 10,450kg into low Earth orbit or 4,540kg into a higher geosynchronous Earth orbit, via the larger Falcon 9.  The still under development, Falcon Heavy, is intended to deliver a massive 53,000kg into low Earth orbit, that is more than twice the payload of a Space Shuttle, all for US$83-128M per launch.  The key point is that this will save the U.S. many billions of dollars over the agreement periods.

These flights are not to be confused with the sub-orbital aspirations of companies such as Virgin Galactic and Copenhagen Suborbitals.  The goal of these companies is to provide space-tourism experiences at lower altitudes.  Virgin Galactic for example offer a US$200,000 sub-orbital experience, sometime in 2014.  To keep this in perspective low Earth orbit minimum is 160km, the International Space Station orbits at 378km, the Space Shuttle could achieve 378km, and Virgin Galactic’s SpaceShipTwo will get you to 109km from sea level.  This experience includes a 3-day training period with your fellow astronauts.  Then a parabolic trajectory flight that will take you to the edge of the atmosphere, where the sky changes from blue to cobalt to finally black and you experience a period of weightlessness, then an assisted glide to Earth, much like a Shuttle re-entry.

Enter, the Dragon

It is the Dragon capsule that most clearly delineates the vision of SpaceX from Orbital.    Dragon is a free-flying, reusable spacecraft and is made up of a pressurized capsule and unpressurized trunk used for Earth to low Earth orbit transport of pressurized cargo, unpressurized cargo, and/or crew members.

Dragon Spacecraft with Solar Panels deployed. Image credit NASA/SpaceX

The Dragon can be rapidly transitioned from cargo to crew capability, with the cargo and crew configurations of Dragon almost being identical.  The exceptions are the crew escape system, the life support system, and onboard controls that allow the crew to take over control from the flight computer when needed.  This focus on commonality and modular construction has minimised the design effort and simplified the human rating process.  This allows systems critical to the space station as well as future Dragon crew safety to be fully tested on uncrewed demonstration flights.

Dragon is designed for the cargo and crew requirements of the International Space Station.  As a free-flying spacecraft Dragon also provides a platform for in-space technology demonstrations, scientific instrument testing, and the extension to lunar and planetary landings.

Expedition 30/31 of the International Space Station

Following the completion of NASA’s flight readiness review, on April 16, 2012, SpaceX was ready to launch on Monday, April 30.  On April 23 a delay was called until the next available launch slot on May 7.  The delay was caused by the need for more software and hardware testing.  The testing is designed to validate the Dragon’s ability to safely fly in close proximity to the space station, a tightly-controlled operating sphere requiring redundant hardware systems, fault-tolerant computers and robust software.

The Falcon 9 rocket carrying, the Dragon capsule, will liftoff from Space Launch Complex 40 at the Cape Canaveral Air Force Station in Florida.

This launch will certainly be a noted event.  In recent times NASA has created NASATweetups around launches.  For example the launch of the Mars Science Laboratory in November last year had simultaneous twitter gatherings in both the US and Australia.  For this SpaceX launch over 1600 people applied for the 50 spaces available to be present at the launch.  Space exploration launches are getting cult followings.

During the flight, SpaceX’s Dragon capsule will conduct a series of checkout procedures to test and prove its systems, and then on May 9 it will perform a “fly-under” of the International Space Station.  This fly-under will come within 2.4km of the International Space Station to validate the operation of sensors and flight systems necessary for a safe approach and rendezvous.  The spacecraft also will demonstrate the ability to abort the rendezvous.  After these capabilities are successfully proven, the Dragon will be cleared to berth with the International Space Station on May 10.

Meanwhile onboard the International Space Station, flight engineers Don Pettit and Andre Kuipers are training for the arrival of the Dragon capsule.  They will use the Canadarm2 to retrieve Dragon and berth it into the harmony node of the International Space Station.  The next day, May 11, the hatch will be opened and one of the crew, perhaps Expedition 30 commander, NASA astronaut Dan Burbank, will be the first to enter the commercial spacecraft.  It will be then unloaded and eventually filled with trash.  After 18 days of docked operations the duo of Pettit and Kuipers will then detach and release Dragon for its splashdown in the Pacific Ocean 400km off the U.S. west coast.

That is one of the first key differences of SpaceX compared to Orbital and the non-commercial operators.  A trash-filled Russian Progress 46 spacecraft departed from the International Space Station on April 19, 2012.  It’s Russian flight controllers will command the Progress 46 for several days of tests, and then send it to burn up in Earth’s atmosphere over the Pacific Ocean.  In addition the International Space Station has had fuel, water, and food deliveries from Japanese and European Space Agency craft.  Before the completion of Expedition 30/31 the first delivery, from an Orbital Cygnus craft, is also expected.  These craft, including Cygnus, are one-off use, being burned up deliberately upon re-entry to the Earth’s atmosphere.

What next after the grocery deliveries?

This May Dragon flight is the first of 12 NASA scheduled resupply flights by SpaceX to the International Space Station using their Falcon9/Dragon combination, a US$1.6B contract.  They also have a solid book of satellite launches all through to the end of 2015.  If SpaceX is “cash flow positive” then Elon Musk expects to make a listing, an initial public offering, of SpaceX sometime in 2013.

In addition to this SpaceX is looking at a number of sites, including Texas, Alaska, California, Virginia, and Florida to build a commercial spaceport.  On of the recent sites discussed in a Federal Aviation Administration environment review document was near Brownesville in Texas.  This private site is located in Cameron County, southern Texas.  If a launch facility were built here, then all rockets departing this installation would head east, over the Gulf of Mexico.  This path would enable the Dragon spacecraft to reach the International Space Station.

During the day-long test of the engineering prototype, SpaceX and NASA evaluators participated in human factors assessments which covered entering and exiting Dragon under both normal and contingency cases, as well as reach and visibility evaluations. Test crew included (from top left): NASA Crew Survival Engineering Team Lead Dustin Gohmert, NASA Astronaut Tony Antonelli, NASA Astronaut Lee Archambault, SpaceX Mission Operations Engineer Laura Crabtree, SpaceX Thermal Engineer Brenda Hernandez, NASA Astronaut Rex Walheim, and NASA Astronaut Tim Kopra. Photo: Roger Gilbertson / SpaceX

All the current planned flights are unmanned, but SpaceX is already developing a manned version of the Dragon capsule.  It recently completed another important milestone – the first NASA Crew Trial, one of two crew tests as part of SpaceX’s work to build a prototype Dragon crew cabin.  For this milestone SpaceX demonstrated that the new crew cabin design would work well for up to seven astronauts in both expected and unusual scenarios.  It also provided SpaceX engineers with the opportunity to gain valuable feedback from both NASA astronauts and industry experts.

Excitingly true to their entrepreneurial spirit, SpaceX has already sold its first launch to the moon.  A lunar mission that gives Pittsburgh-based Astrobotic Technology, a Carnegie Mellon University spin-off, an early lead in a US$32M race to land a privately owned rover on the lunar surface.  The contract, announced on May 6, 2011, reserves a SpaceX Falcon 9 rocket to fly Astrobotic Technology’s lander and rover to the moon as early as December 2013.

Mars is also firmly in the sights of SpaceX, even if only at the conjecture stage at present.  It was reported in 2011 that NASA science hardware would fly to Mars aboard SpaceX’s Dragon capsule.  This so-called “Red Dragon” mission could be ready to launch by 2018, and would carry a cost of about US$400M or less.  Astrobiologist Chris McKay, of NASA’s Ames Research Centre and his colleagues are developing the Red Dragon concept as a potential NASA Discovery mission, a category that stresses exploration on the relative cheap.  NASA is currently vetting three Discovery candidates, one of which it will choose for a 2016 launch.  That mission will be cost-capped at $425 million, not including the launch vehicle.

This still from a SpaceX mission concept video shows a Dragon space capsule landing on the surface of Mars. Image credit SpaceX.

Red Dragon is not in that group of three finalists.  NASA will make another call for Discovery proposals and McKay and his team plan to be ready for that one.  If Red Dragon is selected in that round, it could launch toward Mars in 2018.  Assuming that $425 million cap is still in place, Red Dragon could come in significantly under the bar.

In comparison to the proposed costs of this real expedition Disney recently spent over US$350M on a Mars sci-fi flop.  Disney spent US$250M to make “John Carter” and a further US$100M to market it, making an estimated US$200M loss, Hollywood’s largest loss ever on a film.

It is not clear at present what will happen with NASA’s Mars aspirations after recent Congress budget decisions.  Nonetheless rocket entrepreneur Elon Musk believes he can get the cost of a round trip to Mars down to about US$500,000.  The SpaceX CEO says he has finally worked out how to do it, would reveal further details later this year or early in 2013.

Letting a Dragon loose into space has certainly released a fiery-breath of fresh air into space exploration.

Originally published on Australian Science on April 25, 2012.

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Apr
12
0

The Earth just aged a little bit more

By Kevin Orrman-Rossiter | Filed in Chemistry, Physics, Space Science
This composite image of the Tycho supernova remnant combines X-ray and infrared observations obtained with NASA's Chandra X-ray Observatory and Spitzer Space Telescope, respectively, and the Calar Alto observatory, Spain. It shows the scene more than four centuries after the brilliant star explosion witnessed by Tycho Brahe and other astronomers of that era. Credit: X-ray: NASA/CXC/SAO, Infrared: NASA/JPL-Caltech; Optical: MPIA, Calar Alto, O.Krause et al.

Have you ever had a moment when person responds to you in a way that just makes you feel a little bit older than you did before?  You comment, for example, about a music group to someone, only to be met with that incredulous stare that conveys the message to you that their parents liked that music, and that you must be a little older than you at first appeared.

An international research team just gave the Earth such a moment.  The researchers did this, not by experimenting on musicians, rather by measuring the radioactive decay of samarium-146; one of the isotopes used to chart the evolution of the Solar System.

By using a more precise technique to remeasure the half-life of samarium-146, they shrank the chronology of early events in the solar system, like the formation of planets, into a shorter time span.  It also means some of the oldest rocks on Earth would have formed even earlier.  Some Australian rocks forming as early as 120 million years after the solar system formed.

Understanding how a seemingly simple measurement, such as the half-life of samarium-146, can have such far-reaching results will take us on an exhilarating journey through many areas of science.

How did our Solar System form?

According to current theory, everything in our Solar System formed from stardust several billion years ago.  Some of this dust was formed in giant supernovae explosions.  These explosions then supplied most of the heavy elements for the objects that make up our Solar System.  The synthesis of the elements we see on Earth, in rock samples from the Moon and Mars, as well as from meteorites and asteroids, is a subject of great interest.  By understanding the physics of the nucleo-synthesis of the isotopes of these elements it has become obvious that the dust and molecules that coalesced to form our solar system came from a number of different processes.

Proto-planets. Image credit: NASABlueshift

The formation of the terrestrial planets (the rocky planets Mercury, Venus, Earth, Mars and their respective moons) is generally divided into three major stages based on the different physical processes involved and their respective time scales: (1) the stardust aggregates into planetismals, like individuals forming into swarms of nomadic tribes; (2) then runaway and oligarchic growth of embryos from planetismals resulting several tens to 100 Lunar- to Mars-mass embryos embedded, like mediaeval barons, in a swarm of remnant planetismals; and (3) the final stage of terrestrial planet formation by high-velocity impacts between embryos over a span of ~10-100 million years, forming the planets as we know them.

The Allende meteorite and the age of the Solar System

The age of the Solar System can be defined as the time of formation of the first solid grains in the nebular disk surrounding the proto-Sun.  This age is estimated by dating calcium-aluminium-rich inclusions in meteorites.  All chronology, by convention, is referenced to T0, which is the abbreviation for the age of the oldest known solid material in the solar nebula.

Scientists have found that calcium-aluminum-rich inclusions are some of the oldest objects in the solar system.  These inclusions, roughly millimetres to centimetres in size, are believed to have formed very early in the evolution of the solar system and had contact with nebular gas, either as solid condensates or as molten droplets.

Relative to planetary materials, calcium-aluminium-rich inclusions are enriched with the lightest oxygen isotope and are believed to record the oxygen composition of solar nebular gas where they grew.  Calcium-aluminium-rich inclusions, at 4.57 billion years old, are millions of years older than more modern objects in the solar system, such as planets, which formed about 10-50 million years after them.

In recent research, a US team led by Justin Simon from NASA Johnson Space Centre and University of California Berkeley, studied a specific calcium-aluminium-rich inclusion found in a piece of the Allende meteorite.  Allende is the largest carbonaceous chondrite meteorite ever found on Earth.  It fell to the ground in 1969 over the Mexican state of Chihuahua and is notable for possessing abundant calcium-aluminium-rich inclusions.

Carbonaceous chondritic meteorites are stony meteorites that have not been modified due to melting or differentiation of the parent body.  They formed in oxygen-rich regions of the early, first stage, Solar System so that most of the metal is not found in its free form but as silicates, oxides, or sulfides.  Most of them contain water or minerals that have been altered in the presence of water, and some of them contain larger amounts of carbon as well as organic compounds.  The Allende meteorite is a ‘pristine’ meteorite, so called because its provenance is known.  It was found and sampled under conditions that precluded contamination from terrestrial chemicals and minerals.

Their findings imply that calcium-aluminium-rich inclusions formed from several oxygen reservoirs, likely located in distinct regions of the solar nebula.  Calcium-aluminium-rich inclusions travelled within the nebula by lofting outward away from the sun and then later falling back into the mid-plane of the Solar System or by spiralling through shock waves around the Sun.

Through oxygen isotopic analysis, the team found that meteorite material surrounding the calcium-aluminium-rich inclusion show that late in the calcium-aluminium-rich inclusion’s evolution, it was in a nebular environment distinct from where it originated.  This latter region was closer in composition to the protoplanetary disk, the environment in which the building materials of the terrestrial planets formed.  A protoplanetary disk is an area of dense gas surrounding any newly formed star.  In this case, the calcium-aluminium-rich inclusion formed when our Sun was quite young.

This composite image of the Tycho supernova remnant combines X-ray and infrared observations obtained with NASA's Chandra X-ray Observatory and Spitzer Space Telescope, respectively, and the Calar Alto observatory, Spain. It shows the scene more than four centuries after the brilliant star explosion witnessed by Tycho Brahe and other astronomers of that era. Credit: X-ray: NASA/CXC/SAO, Infrared: NASA/JPL-Caltech; Optical: MPIA, Calar Alto, O.Krause et al.

The formation of the Solar System as we know it today, was complex and dynamic process.  The protoplanetary disk evolves through accretion to the star, the particles and molecules being gravitational attracted to the proto-Sun.  Each particle’s attraction was mediated or dampened by collisions, the viscous drag of the gaseous nebula, coupled with an outward ‘fling’ due to their angular momentum.

Radioactive dating the age of the Solar System

Timescales of early Solar System processes rely on precise, accurate and consistent ages obtained with radiometric dating.  The relative abundance of different nuclei and their correlation or non-correlation with models of their formation and their radioactive decay provide a series of clocks to determine when and how material was formed.

Recent advances in instrumentation now allow scientists to make more precise measurements.  Some of these measurements are revealing inconsistencies in the ages of samples as well as clearing up existing inconsistencies.

For example, recent analysis, by Audrey Bouvier and Meenakshi Wadhwa from Arizona State University, of the meteorite, Northwest Africa 2364, found that the age of the Solar System predates previous estimates by up to 1.9 million years.  They used a radioactive chronometer based on the decay of isotopes of uranium to lead.

By using this lead-lead dating technique these researchers were able to calculate the age of a calcium-aluminium-rich inclusion contained within the Northwest Africa 2364 chondritic meteorite.  In lead-lead dating the lead isotope, 207Pb/206Pb ratios are measured; these lead-207 and lead-209 isotopes are the decay products of the uranium isotopes 235U and 238U respectively.

The study’s findings fix the age of the Solar System at 4.5682 billion years old, between 0.3 and 1.9 million years older than previous estimates.  This relatively small revision to the currently accepted age of about 4.56 billion years is significant since some of the most important events that shaped the Solar System occurred within the first ~10 million years of its formation.

This relatively small age adjustment means that there was as much as twice the amount of iron-60, a certain short-lived isotope of iron, in the early Solar System than previously determined.  This higher initial abundance of this isotope in the Solar System can only be explained by supernova injection.  The researchers believe the supernova event, and possibly others, could have triggered the formation of the Solar System.  By studying meteorites and their isotopic characteristics, they bring new clues about the stellar environment of our Sun at birth.

Planetary formation from a soar nebula. Image credit NASA

This work also helps to resolve some long-standing inconsistencies in early Solar System time scales as obtained by different high-resolution chronometers.  The story is not yet complete, it will be important to conduct high precision chronologic measurements of calcium-aluminium-rich inclusions from other pristine meteorites.  We also need to understand the reasons why the calcium-aluminium-rich inclusions measured previously from two other chondritic meteorites, Allende and Efremovka, have yielded younger ages.

One significant aspect of this study is that it is the first published lead-lead isotopic investigation that takes into account the possible variation of the uranium isotope composition.  Earlier work conducted in Wadhwa’s laboratory by a graduate student Gregory Brennecka, in collaboration with Ariel Anbar, has shown that the uranium isotope composition of calcium-aluminium-rich inclusions, long assumed to be constant, can in fact be highly variable and this has important implications for the calculation of the precise lead-lead ages of these objects.

Using the relationship demonstrated by Brennecka and colleagues between the uranium isotope composition and other geochemical indicators in calcium-aluminium-rich inclusion, Bouvier and Wadhwa inferred a uranium isotope composition for the calcium-aluminium-rich inclusion for which they reported the lead-lead age.

This work can help researchers better understand the sequence of events that took place within the first few million years of the Solar System formation, such as the accretion and melting of proto-planetary bodies.  All these processes happened extremely rapidly, and only by reaching such a precision on isotopic measurements and chronology can we find out about these processes of planetary formation.

The importance of the half-life of the isotope samarium-146

As well as the lead-lead dating technique the radioactive chronometer based on the isotope samarium-146 is one of interest for this story.  Samarium-146, or 146Sm, is unstable and occasionally emits an alpha particle, a helium-4 particle, which changes the atom into a different element, neodymium-142.

As samarium-146 decays slowly—on the order of millions of years—many models use it to help determine the age of the Solar System.  In particular, in models of terrestrial planetary formation, rather than dating calcium-aluminium-rich inclusions in meteorites used in studying early Solar System formation.

Although samarium-146 decays slowly, it is still short compared to the time-scale of solar system evolution.  For a known number of any isotope type, the number of years it takes for this to radioactively decay by half of its number, is called its half-life.  Since samarium-146 emits particles so rarely, it takes a sophisticated instrument to measure this half-life.  The half-life of samarium-146 allows its use as a determinator of the time between the end of its synthesis in the early Solar System and the inclusion of it in a solid body in the solar system.

What scientists look for are disparities in the relative abundances of samarium isotopes in terrestrial rocks and in the relative abundances of samarium and neodymium and neodymium isotopes.  The reason for interest in the samarium-146 to neodymium-142 is that the half-life means that samarium-146 present at the time of solidification would no longer be available for observation at the present-time; it all will have decayed to neodymium-142.  Therefore the isotopic composition of neodymium will vary with the amount of samarium, which was present at solidification.

The researchers remeasured the half-life of samarium-146 using the sophisticated instrument at the Argonne Tandem Linac Accelerator System, Kanazawa University, and the University of Tsukuba in Japan.  What they did was very clever and very precise.

Firstly, they synthesised samples of samarium-146, in three independent nuclear-synthesis reactions, from samples of isotopically enriched samarium-147.  The different techniques gave analysis samples with different contaminants and samarium-146 levels.  Secondly, they measured the decay of these samples over a period of months using highly accurate detectors.

The Argonne Tandem Linac Accelerator System was then used as a mass spectrometer, in two different experimental set-ups, to pick out the small number of samarium-146 in the samples, one in tens of billions of atoms.  These measurements took into account contributions from contaminants such neodymium-146, which caused contamination problems in earlier experiments.  Neodymium-146 has the same atomic mass as samarium-146, and in mass spectroscopic measurements they cannot easily be separated.

By accurately counting the number samarium-146 atoms and tracking the particles that the sample emits, the team came up with a new calculation for its half-life: just 68 million years.

This is significantly shorter than the previously used value of 102.6 and 103.1 million years of recent (1966 and 1987 respectively) measurements.  At the same time the result is closer to earlier measurements of ~50 million years and 74 million years from 1953 and 1964 respectively.

A new samarium-146 half-life measurement; now what?

The new value patches some holes in current understanding.  The new time scale now matches up with a recent, precise dating taken from a lunar rock, and is in better agreement with dates obtained with other chronometers.

Applying this new half-life to rocks from Greenland and Australia gives them revised ages.  These rocks are now dated to be 50 million years older than previously thought.  That is they were formed only 120 million years after T0, the time of solar system formation, rather than the 170 million years from previous results.  Similarly rocks from Quebec were found to be over 80 million years older than previous measurements.  These are now found to have formed 205 million years, rather than 287 million years, after Solar System formation.  These results illustrate that the events that formed terrestrial rocks occurred at much earlier ages than we even recently thought.

Analyses of moon rock samples have also shown an increase in their ages, in this case by over 70 million years.  These are now found to have formed 170 and 175 million years, rather than 242 and 250 million years respectively, after Solar System formation.  These new lunar results now bring ages of these rocks, using two different chronometers, the samarium-146 and lead-lead techniques, into the same ranges.

The early days of Earth and the other terrestrial planets are looking quite different than previously thought.  All this is thanks to some precision measurements of the half-life of an extinct isotope of an exotic rare-earth element, samarium.

 

First published as: “These rocks just got a little bit older” on Australian Science.

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Mar
31
0

“Smarter, more competitive, more productive”, the Chief Scientist, Professor Ian Chubb on Australia’s Future in Science and Technology

By Kevin Orrman-Rossiter | Filed in Philosophy of science, Science communication, Science policy

There is no doubt in the mind of Australia’s Chief Scientist, Professor Ian Chubb, the future will be shaped by science technology, engineering and mathematics.  Unfortunately, he finds that at present the standing of science, as an expert authority, is being challenged.  Furthermore, Ian Chubb finds that the science message is getting lost in the white noise of the mainstream media.  I was heartened to hear his positive words about science communication, social media, science and technology education and innovative Australian workplaces.

These were the messages from Ian Chubb at an address he gave as part of NICTA’s Big Picture Seminar series on Wednesday March 28, 2012 at the University of Melbourne.

It was refreshing to see Australia’s Chief Scientist out and about and addressing public forums such as this one.  Although judging by the faces, the suits and the overheard conversations at the drinks and nibbles prior to the address, I think this was definitely a speech to the science and technology faithful.  That is a pity, his words were worth  exposure and considered comment in the mainstream Australian media.

Prof. Ian Chubb at the Climate congress, Copenhagen 2009, March 10-12. Opening session.

Professor Ian Chubb emphasises Mathematics, Engineering and Science provide the enabling skills and knowledge that underpin every aspect of modern life. They help us understand the natural world and enable us to respond as humans to this world with a constructed view aimed at improving the lot of human kind.

In Australia, as in many economies, we have observed a decline in the number of people choosing a career in these disciplines.  Not only that, the STEM subjects (Science Technology Engineering and Mathematics), as he called them, are taken for granted or simply ignored.   Although it is obvious without at least an appreciation of these subjects, a modern citizen is hampered in their ability to critically evaluate and make informed decisions about the issues that are shaping their future. Among his many roles as Australia’s Chief Scientist, Professor Ian Chubb has been charged with examining this decline and offering strategies to address it.

Professor Ian Chubb is eminently suited to this task.  He was appointed to the position of Chief Scientist on 19 April 2011 and commenced the role on 23 May 2011. Prior to his appointment as Chief Scientist, Professor Ian Chubb was Vice-Chancellor of the Australian National University.  Professor Chubb’s research focused on the neurosciences.  Although he jokingly said on the night he would prefer not to be quizzed, on science specifics, by such an informed audience.  He has co-authored some 70 full papers and co-edited one book all related to his research. In 1999 Professor Chubb was made an Officer of the Order of Australia (AO) for “service to the development of higher education policy and its implementation at state, national and international levels, as an administrator in the tertiary education sector, and to research particularly in the field of neuroscience”. In 2006 he was made a Companion (AC) in the order for “service to higher education, including research and development policy in the pursuit of advancing the national interest socially, economically, culturally and environmentally, and to the facilitation of a knowledge-based global economy”.  I certainly expect to see some informed, well-researched and erudite outputs from his office over the next few years.

On the evening he emphasized that we in the audience have an important role to play.  He seized upon two, in my mind important aspects: the first was the quality and engagement of science teaching in schools and the second was science communication into the mainstream consciousness.

Ian Chubb sees a key way to develop a more scientifically and technologically literate Australia is to enable the sciences at the primary and secondary school level.  He sees this as the way to demonstrate how useful science; scientific concepts and processes are to everyday lives.  To do this we need to have inspirational teachers.  Teachers who are creative and imaginative and can make the subject interesting without being simplistic.  It still needs to be challenging, that is part of science.  He sees CSIRO outreach programmes being and integral part of this.  By tackling the problem at this level he believes we can make science relevant and part of the community values.

The second part focused on scientists doing media better and media doing science better.  This he trusts will change the current state of ill-informed debate that occurs about many subjects in the public media.  He, thankfully, pressed home that communicating science better needs to be a goal of the practicing scientists, and the learned science, technology, engineering and mathematics professional.  The existing discipline silos also hamper us taking advantage of what we do have.  The pieces of the jigsaw are still separated on the table rather than being used to advantage.

Ian Chubb is also a fan of social media.  I see eye-to-eye with him on that social media can get science into the mainstream of people’s consciousness.  It can bring immediacy about the scientific process; the rigour, analysis and observation that are part of science in practice.  He also emphasized that we take a PhD to mean “educated intelligent person” rather than the narrow view of “researcher” as is commonly held.  The universities and commercial workplaces need to see these people as key to creating an innovative workplace.  A workplace that will transform traditional Australian economies.

In conclusion he saw that for Australia to become smarter, more competitive, and more productive we need to have a cultural change.  A change that enables people to understand that science and technology is good and a common cause.  A change, that needs to start right now.  I am enthused and ready, how about you?

Originally published on Australian Science March 30, 2012.

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Mar
28
0

Who found the water on the Moon?

By Kevin Orrman-Rossiter | Filed in Astrobiology, Science communication, Space Science

At just over two tonnes, the second stage of an Atlas V rocket makes for an unusual ‘kinetic probe’.  Nonetheless on October 9, 2009 NASA deliberately impacted a spent Centaur rocket into the lunar south polar crater Cabeus.  The target area was a permanently shadowed region within this crater.  The impact, not surprisingly, ejected a spectacular plume of debris, dust, and vapour.

Science experiment: observe the system, perturb it, and measure what happens

The US scientists had thrown a heavy object at the Moon.  They then threw all the instruments possible to monitor the impact.  The prize was a decades-long search to directly find water on the Moon.

The impact would have been majestic to watch.  Picture those slow motion images of Apollo astronauts on the Moon.  Hold that thought and then imagine the impact.  An observer could marvel at the slow motion, low gravity, return of the dust and debris cloud to the Moon’s surface.  If you could see in the infrared, the impact flash lasts for 10 seconds.  There is a cloud of debris, dust, and vapour rising.  At eight seconds the ejecta cloud is 4.5km in diameter, in the ultra-violet spectrum, the plume is 10km in diameter.  At 20 seconds after impact the ejecta cloud was is at its maximum diameter of 8.5km and the plume has reduced to little less than 10km.

The observer would be watching a science experiment on a grand scale.

The observer in this experiment was neither you nor I it was a trailing “shepherding spacecraft”.  The Centaur had propelled NASA’s Lunar Reconnaissance Orbiter and Lunar Crater Observation and Sensing Satellite to the Moon.  Shortly after launch the Lunar Reconnaissance Orbiter had separated to go on its own mission.  Once in lunar orbit the Centaur had vented its remaining fuel.  Control was then assumed, for the next four months, by the Lunar Crater Observation and Sensing Satellite as the shepherding satellite.  During this next period the shepherding satellite manoeuvred the Centaur to allow the Sun to bake-out residual water and volatiles.  This was to ensure that no contaminant chemicals were passengers to the lunar impact site.  The Centaur’s fuel was a volatile combination of liquid hydrogen and liquid oxygen, both chemicals that were to be scanned for in the impact cloud.  The Lunar Crater Observation and Sensing Satellite also calibrated its instruments, then, targeted the Centaur to impact with the Moon.  Four months of meticulous preparation.

LCROSS spacecraft with Centaur stage, image credit NASA

The Lunar Crater Observation and Sensing Satellite carried nine instruments, including cameras, spectrometers, and a radiometer.  The spectrometers measured the reflected light at different wavelengths.  These enabled the identification of the chemicals present in the ejected cloud.

Near-infrared absorbance attributable to water vapour and ice, and ultraviolet emissions attributable to hydroxyl radicals (OH-) support the presence of water in the debris.  The researchers determined from these observations that there was over 5%, by mass, of water ice in the lunar regolith of the impact site.  Certainly this is small by terrestrial soil standards, but more substantial than most earlier estimates.

Over a year after the impact, in the October 22, 2010 issue of the journal Science, the results of this experiment were delivered to the world’s attention.  This certainly marked a defining moment for lunar scientists, directly confirming the availability of water on the moon.  It was however neither the first nor last word on this.

Cabeus crater LCROSS impact site, photo credit NASA

Early attempts

Since the first lunar samples were carried back to earth by Apollo astronauts, in the late 1960s, scientists have operated under the presumption that the moon was entirely dry.  In total 382kg of lunar material was bought to Earth by the Apollo mission astronauts and a further 0.32kg by the unmanned USSR Lunar missions.  New analyses of these rocks with improved analytical techniques have made it possible to perform highly sensitive isotopic measurements on very small lunar grains.  These analyses are revealing water in Apollo samples that were once thought to be dry.

Well before these new studies, scientists had been puzzling about why more water was not seen on the moon.  It was thought that volatile materials, such as water, could be accumulating at the moon’s permanently shaded polar regions.  Here they could be trapped for geological periods of time without significant loss.  The in 1998, the orbiting Lunar Prospector spacecraft measured the abundance of elements on the moon’s surface using neutron spectroscopy.  This provided compelling evidence for enhanced hydrogen concentrations, and by inference water, at both of the lunar poles.

In 1999 the Cassini spacecraft flew by the moon on its way to Saturn.  It turned its Visual and Infrared Mapping Spectrometer to the moon.  By measuring the surface reflectance of light from the moon scientists found absorption attributed to hydroxyl and water on the sunlit surface of the moon.  These results were not published until 10 years later, in October 2009.  The reason was renewed interest in water on the moon.

On October 22, 2008 the Indian Space Research Organisation launched Chandrayaan-1, on its lunar mission.  One of its major scientific missions was to look for water on the moon.  It had three different instruments ready to make 2008-10 an interesting period for lunar water exploration.

Chandrayaan-1, India’s lunar water finder

The Chandrayaan-1 story is told in detail elsewhere.  Here I intend to showcase the marvellous outcome of Chandrayaan-1′s water finding experiments.  Perhaps the most exciting of all these was one of the simplest.  This was the CHandra’s Altitudinal Composition Explorer (CHACE) on board the Moon Impact Probe.

On November 14, 2008 (the birthday of the late Pandit Jawaharlal Nehru, India’s 1st Prime Minister) the Moon Impact Probe became the first Indian built object to reach the surface of the Moon.  The probe was a 34kg box-shaped object containing a video image system, radar altimeter, and The CHACE mass spectrometer.

Symbolically the Indian tricolour was painted on three sides of the Moon Impact Probe.  This enables India to also lay claim to having the “Indian tricolour placed on the Moon”.  Needless to say that “placing” in this case was a hard landing in the Moon’s south polar region near the Shackleton crater, flying over the Malapert mountain en route.

The CHACE mass spectrometer took 650 spectra of the tenuous lunar atmosphere during its 1487-second, 98km, plunge to the lunar surface.  Tenuous is right the atmosphere even on the sunlit side is only 7/10,000,000,000th of the Earth’s atmosphere.

The mass spectrometer was tuned to look find water and direct evidence of water it did find.  The team leader of the experiment, Dr S M Ahmed, remembers, “We all were jumping when we saw water was literally pouring out of our instrument” on November 14, 2008.  The Indian scientists had established that the dominant species of the tenuous sunlit lunar atmosphere were H2O, N2, and CO2.

These results were not published until August 6, 2010 after being confirmed (on August 22, 2009) and complemented by the results from two of the other 11 instruments that formed the scientific payload of Chandrayaan-1.  Amongst the instruments on Chandrayaan-1 were the Moon Mineralogy Mapper (M3) and Miniature Synthetic Aperture Radar (Mini-SAR) from NASA.  The Moon Mineralogy Mapper has covered nearly 97% of the lunar surface, some of the other instruments have covered more than 90%.

Water detected at high latitudes on the Moon, image credit NASA

A detailed analysis of the data obtained from Moon Mineralogy Mapper, has clearly indicated the presence of water molecules on the lunar surface extending from the lunar poles to about 60 degrees latitude. Hydroxyl, a molecule consisting of one oxygen atom and one hydrogen atom, was also found in the lunar soil.

The Moon Mineralogy Mapper measured the intensity of reflected sunlight from the lunar surface at infrared wavelengths, splitting the spectral colours of the lunar surface into small enough bits revealing finer details of the lunar surface composition.  This enabled identification of the presence of various minerals on the lunar surface that have characteristic spectral signature at specific wavelengths.  Since reflection of sunlight occurs near the moon’s surface, such studies provide information on the mineral composition of the top crust of a few millimeters of the lunar surface.

The findings from Moon Mineralogy Mapper clearly showed a marked signature in the infrared region of 2.7 to 3.2 micron in the absorption spectrum, which provided a clear indication of the presence of hydroxyl (OH) and water (H2O) molecules on the surface of the Moon closer to the polar region.  It was also concluded that they are in the form of a thin layer embedded in rocks and chemical compounds on the surface of the moon and the quantity is also extremely small of the order of about 700ppm.

These molecules could have come from the impact of comets or radiation from the sun. But the most probable source could be low energy hydrogen carried by solar wind impacting on the minerals on lunar surface.  This in turn could form OH or H2O molecules by deriving the oxygen from metal oxide.

Following these findings, the scientific team revisited the data from NASA’s Deep Impact Mission launched in 2005 which carried an instrument similar to Moon Mineralogy Mapper. Deep Impact Probe observed the moon during the period June 2 to 9, 2009.  As previously mentioned the Moon Mineralogy Mapper observations are further strengthened by results obtained from the analysis of archived data of the Cassini probe.

Further to these findings, ice was detected in small polar craters (2-15km in diameter) that are not visible from the Earth.  These north polar craters have sub-surface water ice located at their base.  The interior of these craters is in permanent shadow from the Sun.  Although the total amount of ice depends on its thickness in each crater, it’s estimated there could be at least 600 million metric tons of water ice.

This water was detected using the mini-SAR instrument.  Mini-SAR is a lightweight (less than 10kg) synthetic aperture imaging radar.  It uses the polarization properties of reflected radio waves to characterize surface properties.  Looking at their internal roughness this instrument could detect whether craters were newly formed.  It found the water by looking for craters that gave anomalous signals.  Signals that were consistent, however, with them having water in their base.

How did the water come to be there?

Using methods, both direct and indirect, we now know that water is present on the moon.  We even have a good estimate of the amount of it that is present and were it is located.  How were these reservoirs of lunar water formed?  Studies published in 2011 suggest that water was acquired by both the Earth and Moon after the Moon’s formation.  Geochemical analysis of the rocks retrieved by the Apollo missions show the lunar and terrestrial water are isotopically distinct.  It remains a conundrum how the Earth and the Moon could have sampled water from different origins.

The conventional explanation for ice in polar craters like Cabeus – whose floor is in permanent shadow and thus hovers near 40 degrees above absolute zero – is that icy asteroids or comets strike somewhere on the Moon, and some of the resulting water vapour reaches a permanently shadowed crater’s deep chill and freezes out there.  This cold trapping would only fill the empty space in the regolith, not form nearly pure ice.  Regolith is the name for the lunar ‘soil’, more like dust as it contains no organic matter that would make it truly soil.

No one knows how the subsurface ice would form.  Now that it has been blasted into view, its presence confirmed, scientists can move their thoughts to determining how it came to be there, in the form that it is.

Still that is the beauty and fun in science, understanding how reality comes to be the way it is.

Water on the Moon, so what?

So why the interest in whether there is water on the moon?  I would suggest that there is a one word succinct answer to this question; curiosity.  Science by its nature is a curiosity-driven enterprise.  How did the universe come to be the way it is?  This I suspect is, ultimately, the question behind most if not all scientific enterprise.  The quest for water on the moon was also driven by the need to sustain astronauts returning to the Moon.  Readily accessible water is a necessity to sustain a moon-base.  Human exploration, although always framed in economic, or national, or in this case human-kind language is, I suspect, deeply motivated by human curiosity.

Since then, the Obama-administration and now Congress have turned their backs on sending humans to the Moon.  This decades-long push by NASA, with help from their friends, to find water will benefit the others with lunar aspirations.  The Indians have a Space 2025 vision to follow up Chandrayaan-1 with further unmanned Moon voyages.  In addition they have recently announced that the Indian Air Force has responsibility for developing a viable astronaut training programme for the purpose of  undertaking future manned spaceflights.

ISRU/NASA Water processing demonstration concept

The Russian newspapers have recently trumpeted that Russia will put men on the Moon by 2030 – although, officially Russia’s most up to date planning covers to the year 2015.  Japan has a proposed unmanned lunar probe for launch ‘some time in the 2010 decade’.  This follows up on a successful September 14, 2007 launch of its lunar orbiter, Kaguya. Meanwhile the first spacecraft of the Chinese lunar exploration programme, the unmanned lunar orbiter Chang’e 1, was successfully launched from Xichang Satellite Launch Center on October 24, 2007.   A second unmanned orbiter, Chang’e 2, was launched successfully on October 1, 2010.  Chang’e 3, China’s first lunar rover, is expected to launch in 2013.  A manned expedition may occur in 2025-2030.

The 2020-30 decades could herald an intense, multinational, focus on water on the Moon.

The essay was first published on March 26, 2012 on the Australian Science website.  It is also an entry in the Bragg UNSW Press Prize for Science Writing 2012.

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Mar
24
0

Two Genes Do Not a Voter Make

By Kevin Orrman-Rossiter | Filed in Decision making, Social neuroscience

Voting behavior cannot be predicted by one or two genes as previous researchers have claimed, according to Evan Charney, a Duke University professor of public policy and political science.

In “Candidate Genes and Political Behavior,” a paper published in the February 2012 American Political Science Review, Charney and co-author William English of Harvard University call into question the validity of all studies that claim that a common gene variant can predict complex behaviors such as voting.

They use as an example a 2008 study by James H. Fowler and Christopher T. Dawes of the University of California, San Diego which claimed that two genes predict voter turnout. Charney and English demonstrate that when certain errors in the original study are corrected — errors common to many gene association studies — there is no longer any association between these genes and voter turnout.

“The study of Fowler and Dawes is wrong,” Charney said. “Two genes do not predict turnout. We re-ran the study using all of their assumptions, equations, and data and found that their results were based upon errors they made. When we corrected the errors, there was no longer any association between these two genes and voter turnout.”

Charney and English also document how the same two genes that Fowler and Dawes claimed would predict voter turnout are also said to predict, according to other recently published studies, alcoholism, Alzheimer’s disease, anorexia nervosa, attention deficit hyperactivity disorder, autism, depression, epilepsy, extraversion, insomnia, migraines, narcolepsy, obesity, obsessive compulsive disorder, panic disorder, Parkinson’s disease, postpartum depression, restless legs syndrome, premature ejaculation, schizophrenia, smoking, success by professional Wall Street traders, sudden infant death syndrome, suicide, Tourette syndrome, and several hundred other behaviors. They point to a number of studies that attempted to confirm these findings and could not.

“Researchers the world over are using data sets that contain behavioral information about study participants along with limited genetic data for a handful of their genes,” Charney said. “Often, the genetic data contained in these various data sets is limited to the very same four or five genes. The result is that the same genes are now said to predict an astonishing array of human behavior.”

“How could one common gene variant possibly predict so many diverse behaviors?” Charney asked. “And what are the odds that the very same handful of genes — out of an estimated 25,000 to 30,000 genes — will miraculously turn out to be the genetic key to all of human behavior?”

Charney and English also note that the underlying assumption of gene association studies is at odds with our current understanding of the relationship between genes and complex human behaviors, such as political behavior.

“There is a growing consensus that complex traits that are heritable are influenced by differences in thousands of genes interacting with each other, with the epigenome (which regulates gene expressivity), and with the environment in complex ways,” Charney said. “The idea that one or two genes could predict something like voting behavior or partisanship violates all that we now know about the complex relationship between genes and traits.”

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Mar
19
0

How much does antimatter weigh?

By Kevin Orrman-Rossiter | Filed in Philosophy of science, Physics, Science communication

A pulse of particles speeds into the vacuum chamber.  Positrons, 20,000,000 antimatter particles, clumped in a pulse one nanosecond deep.  Like a silent, angry swarm they are targeted into a porous silica target.  The positrons are confined by a magnetic field, increasing their interaction with the silica.  Some attract electrons and synthesize into positronium, a hybrid unstable ‘molecule’.  Before it can decay the positronium is excited first by a burst of ultra-violet laser light.  Then a second burst, this time in the infrared.  With each excitation the positronium puffs-up. The still bound, positron and electron orbit further and further away from each other.  Decreasing their opportunity to meet.  Increasing the lifetime of the positronium.  Eventually they meet.  They annihilate.  Mutually destructing in a soundless flash of energy.  A pair of gamma rays to remind us of a nanosecond long courtship.

Producing positronium, binding the negatively charged electron with its antimatter equivalent, the positively charged positron, is not a normal occurrence in our world.  If this experiment sounds a little like science fiction, the reason for doing it is part of an even more exotic tale.  This laboratory experiment is to produce ‘long-lived’ positronium is so that the researchers can measure the effect of gravity on it.  Published in January 2012, this success represents 10 years of hard work for Allen Mills and his team from the University of California, Riverside.

The utra-high vacuum chamber at the Positron Lab, UC Riverside

The positron is the antimatter version of the electron.  It has the identical mass to the electron, but a positive charge.  The researchers are trying to find whether matter and antimatter behave the same way under gravity.  That is, do they weigh differently?  If they find such behaviour it would truly rock the physics world.

Antimatter.  The idea of it is weird.  The idea of weighing it is stranger still.

The weirdness of antimatter

Antimatter has been one of the most fascinating fields of research ever since the prediction of its existence by Paul Dirac in 1929.  Paul Dirac solved the basic equations of quantum mechanics.  In doing so he found their solution implied the existence of antimatter particles.  At the time most physicists, Dirac included, thought the idea was preposterous.

Within a short time, experimenters looking at cosmic rays bombarding the Earth found particles that behaved like electrons, but with a positive charge.  In 1932 Carl Anderson carried out the definitive experiments demonstrating the existence of the anti-electron, naming it the positron, and being awarded the Nobel Prize in 1936 for his discovery.

3D image of Antihydrogen

Dirac had postulated in 1931 that each of the fundamental particles has an equivalent antimatter partner.  Furthermore, when matter and its antimatter opposite come into contact they annihilate each other, releasing energy into two equal energy photons.  Their energy is given by Einstein’s famous equation E=mc².  This latter relationship has been much exploited by science fiction writers.  Matter – antimatter reactions powered the star-ship USS Enterprise in the 60s hit TV show Star Trek.

Work with high-energy antiparticles is now commonplace in physics and materials science.  Anti-electrons are used regularly in the medical technique of positron emission scanning tomography.  Perhaps more importantly, the equivalence model of matter and antimatter has been fully incorporated into the Standard Model of Particle Physics.  Matter particles and their anti-matter pairs have the same mass and equal, but opposite charge.

The most important point in all of this focusses on when our universe came into being, the Big Bang.  Models of the Big Bang predict that equal amounts of matter and antimatter were formed initially.  Ordinary matter is clearly what our observable Universe is made of today.  Where is the antimatter?  A glaring, niggling, imbalance that begs for an explanation.

This imbalance could be explained by a slight difference in one of the fundamental properties of particle-antiparticle pairs (such as charge or mass).  There isn’t yet any experimental evidence for such a difference.  Another alternative might be a difference in their gravitational attractiveness.  It is widely expected that the gravitational interaction of matter and antimatter should be identical.  If they were not, then this could explain the preponderance of matter in our universe.

Elementary antimatter particles naturally occur in radioactive decays and in cosmic radiation.  Some of them, such as the positron and the antiproton, have been studied extensively and even compared to their matter equivalents.  Measurements with charged antiparticles are difficult because gravity is a far weaker force than the electromagnetic force.  The first experiments to measure the gravitational attraction of antimatter were at the University of Stanford and CERN in 1974 and 1993 respectively.  Both used charged antimatter particles.  The experiments were marred by stray electric fields and did not produce satisfactory results.

Trying to do experiments like this requires precision and reproducible backgrounds.  The world is a rather messy place to measure these relationships.  Neutral positronium, such as in Mill’s experiments, or an anti-atom could be used to test the effect of gravity on antimatter for the first time, because it is immune to stray electromagnetic fields that have hampered the previous studies with charged antimatter particles.

Does antimatter fall down?

Understanding gravity has proven to be a little more complicated than falling apples.  To the Greek philosopher and polymath Aristotle, the concept that heavy objects fell faster than light objects was obvious.  His elegant, but fanciful, notion persisted well into the Middle Ages.  The Italian physicist, mathematician, and astronomer Galileo Galilei successfully challenged Aristotle’s impractical theories of motion.  Experiments using the swing of pendulums proved him correct.  Observing their swing rates was more practical than the dropping of objects from the Leaning Tower of Pisa, as Galileo had originally proposed.

Galileo also put forward the basic principle of relativity, that the laws of physics are the same in any system that is moving at a constant speed in a straight line, regardless of its particular speed or direction.  Hence, there is no absolute motion or absolute rest.  This principle is central to Einstein’s special theory of relativity.

The key point under consideration here is the correlation between inertial mass and gravitational mass.  This is the correlation between the forces measured on a mass when it is falling under gravity or being accelerated.  The earliest experiments were done by English natural philosopher Isaac Newton and improved upon by the German mathematician and astronomer Friedrich Wilhelm Bessel in the 1820s.

The problem is that Newton’s theories and his mathematical formulae did not and do not explain the equivalence of the behavior of various masses under the influence of gravity, independent of the quantities of matter involved.  The observation that the gravitational mass and the inertial mass is the same for all objects is unexplained within Newton’s Theories.  The experiments of Galileo Galilei, decades before Newton, established that objects that have the same air or fluid resistance are accelerated by the force of the Earth’s gravity equally, regardless of their different inertial masses. Yet, the forces and energies that are required to accelerate various masses is completely dependent upon their different inertial masses, as can be seen from Newton’s Second Law of Motion, F = ma.

Precision measurements by the Hungarian physicist Loránd Eötvös originally in 1885, and then again with improved instruments and precision between 1906 and 1909, established the universality of Newton’s law of gravitation.  These were followed with a series of similar but more accurate experiments, these included experiments with different types of materials, on moving ships and in different locations around the Earth.  These experiments demonstrated the equivalence of gravitational and inertial mass for ordinary matter.  In turn, these experiments led to the modern understanding of the equivalence principle encoded in general relativity, which states that the gravitational and inertial masses are the same.

So far, so good, for understanding the behaviour of ordinary matter.  Rather than disembodied logic alone, the combination of experiment, measurement, and sound reasoning proving to be the correct way to discern the laws that represent reality.

Gravity is now best described by general relativity.  General relativity is a classical theory that does not imply the existence of antimatter.  In the 1980s a quantum-mechanical formulation of gravity allowed for non-Newtonian contributions to the force which might lead to a difference in the gravitational force on matter and antimatter.

A number of theories propose how differential interactions between matter and antimatter may be explained.  It must also be pointed out that numerous models and experiments with matter have been used to derive upper limits on the possible differences in the nature of such gravitational attractions.

Direct investigation of antimatter, experimentally, is characterised by an almost complete lack of data.

The experimenters

Allen Mills is not alone in his quest to measure the weight of antimatter.

In 2011 the AEgIS collaboration at CERN, had funding approved to use antihydrogen to measure any difference in the gravitational force on matter and antimatter.  CERN is Europe’s particle-physics research lab located near Geneva in Switzerland.  Perhaps currently best known for its search for the Higgs boson, the co-called God particle.  The funding scale of the AEgIS experiment (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) is more modest.  It’s goal, to create a horizontal beam of antihydrogen and to study its free fall in the Earth’s gravitational field with a matter wave interferometry apparatus, is scientifically equally far-reaching.

The quest to create, trap and study antihydrogen is now entering its third decade at CERN.

In 2002, the ATHENA experiment at CERN’s Antiproton Decelerator was the first to produce copious amounts of cold antihydrogen, the simplest atomic antimatter system.  The ATHENA (AnTiHydrogEN Apparatus) experiment had the objective to produce, to store and to study antihydrogen at extremely low temperatures, at less than 1 Kelvin temperature.  The goal was to compare the energy levels of antihydrogen and hydrogen with extreme accuracy.  The ATHENA set-up was used as a proof of concept in this case for the successor experiment AEgIS.

The antiprotons supplied by the Antiproton Decelerator were trapped and cooled, and brought into overlap with positrons from a radioactive sodium source in a cylindrical Penning trap.  The produced anti-atoms, no longer confined in the charged-particle trap, drifted radially outward and annihilated on the electrodes.  ATHENA’s sophisticated detector allowed the temporally and spatially resolved reconstruction of these annihilation events.

During the data taking periods in 2003 and 2004, the experimental parameters were optimized in order to maximize the antihydrogen production rate, and the temperature and internal quantum states of the anti-atoms were determined.  ATHENA was not configured to measure the gravitational attraction of antihydrogen.  Data taking with ATHENA has now ended.

It was collaborators from the ATHENA experiment, along with new groups from other institutes, that have designed the successor experiment, AEgIS, with the aim of performing gravitational studies with antimatter.  The AEgIS proposal was submitted in January 2008 and approved by the CERN Research Board in December 2008.  Construction began in early 2010.

Experimental area at CERNs Antiproton Decelerator Hall

Meanwhile the CERN group has been building on its expertise for the production and trapping of antihydrogen.  A new experimental collaboration called ALPHA (Antihydrogen Laser PHysics Apparatus) is another successor to ATHENA.  In late 2010 the ALPHA group managed, 38 times to confine single antihydrogen atoms for 172 milliseconds.  At the time the spokesperson Jeffrey Hangst said, “We’re ecstatic.  This is five years of hard work.”

By July 2011 they had confined seven antihydrogen anti-atoms for 1,000 seconds, extending their earlier results by nearly four orders of magnitude.  To compare with these CERN successes, Mills, in his late 2011 experiment, produced 12 positronium atoms that did not annihilate until they hit the chamber wall.  This journey of a few centimetres takes about a microsecond.

Based on these results Mills believes he can produce a collimated, long-lived beam for the direct measurement of the gravitational free fall of positronium atoms.

Kudos and plaudits

We have in 2012 then, two experiments, both different in their experimental make-up.  Both are trying to measure the gravitational free-fall of antimatter: one using antihydrogen, one using positronium.  Assuming that both will be successful, then one will be used as a confirmation of the results of the other.

This is how great science is done.  Great scientists are nonetheless people.  People are competitive.  In years to come, the science textbooks will record, and perhaps laud, who was first to measure the weight of antimatter.

Originally published as “Weighty thoughts on antimatter” on March 16 2012 in Australian Science.

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Mar
9
0

Hubble finds a dark matter puzzle

By Kevin Orrman-Rossiter | Filed in Physics, Space Science

Astronomers using data from NASA’s Hubble Telescope have observed what appears to be a clump of dark matter left behind from a wreck between massive clusters of galaxies. The result could challenge current theories about dark matter that predict galaxies should be anchored to the invisible substance even during the shock of a collision. Abell 520 is a gigantic merger of galaxy clusters located 2.4 billion light-years away. Dark matter is not visible, although its presence and distribution is found indirectly through its effects. Dark matter can act like a magnifying glass, bending and distorting light from galaxies and clusters behind it. Astronomers can use this effect, called gravitational lensing, to infer the presence of dark matter in massive galaxy clusters.

This technique revealed the dark matter in Abell 520 had collected into a “dark core,” containing far fewer galaxies than would be expected if the dark matter and galaxies were anchored together. Most of the galaxies apparently have sailed far away from the collision.

Merging Galaxy Cluster Abell 520

“This result is a puzzle,” said astronomer James Jee of the University of California in Davis, lead author of paper about the results available online in The Astrophysical Journal. “Dark matter is not behaving as predicted, and it’s not obviously clear what is going on. It is difficult to explain this Hubble observation with the current theories of galaxy formation and dark matter.”

Initial detections of dark matter in the cluster, made in 2007, were so unusual that astronomers shrugged them off as unreal, because of poor data. New results from NASA’s Hubble Space Telescope confirm that dark matter and galaxies separated in Abell 520.

One way to study the overall properties of dark matter is by analyzing collisions between galaxy clusters, the largest structures in the universe. When galaxy clusters crash, astronomers expect galaxies to tag along with the dark matter, like a dog on a leash. Clouds of hot, X-ray emitting intergalactic gas, however, plow into one another, slow down, and lag behind the impact.

That theory was supported by visible-light and X-ray observations of a colossal collision between two galaxy clusters called the Bullet Cluster. The galactic grouping has become an example of how dark matter should behave.

Studies of Abell 520 showed that dark matter’s behavior may not be so simple. Using the original observations, astronomers found the system’s core was rich in dark matter and hot gas, but contained no luminous galaxies, which normally would be seen in the same location as the dark matter. NASA’s Chandra X-ray Observatory was used to detect the hot gas. Astronomers used the Canada-France-Hawaii Telescope and Subaru Telescope atop Mauna Kea to infer the location of dark matter by measuring the gravitationally lensed light from more distant background galaxies.

The astronomers then turned to the Hubble’s Wide Field Planetary Camera 2, which can detect subtle distortions in the images of background galaxies and use this information to map dark matter. To astronomers’ surprise, the Hubble observations helped confirm the 2007 findings.

“We know of maybe six examples of high-speed galaxy cluster collisions where the dark matter has been mapped,” Jee said. “But the Bullet Cluster and Abell 520 are the two that show the clearest evidence of recent mergers, and they are inconsistent with each other. No single theory explains the different behavior of dark matter in those two collisions. We need more examples.”

The team proposed numerous explanations for the findings, but each is unsettling for astronomers. In one scenario, which would have staggering implications, some dark matter may be what astronomers call “sticky.” Like two snowballs smashing together, normal matter slams together during a collision and slows down. However, dark matter blobs are thought to pass through each other during an encounter without slowing down. This scenario proposes that some dark matter interacts with itself and stays behind during an encounter.

Another possible explanation for the discrepancy is that Abell 520 has resulted from more complicated interaction than the Bullet Cluster encounter. Abell 520 may have formed from a collision between three galaxy clusters, instead of just two colliding systems in the case of the Bullet Cluster.

A third possibility is that the core contained many galaxies, but they were too dim to be seen, even by Hubble. Those galaxies would have to have formed dramatically fewer stars than other normal galaxies. Armed with the Hubble data, the group will try to create a computer simulation to reconstruct the collision and see if it yields some answers to dark matter’s weird behavior.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Md., conducts Hubble science operations. STScI is operated by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.

Source: NASA

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Mar
6
1

Poor sleep increases risk for health problems

By Kevin Orrman-Rossiter | Filed in Psychology

Researchers have shown that older adults who sleep poorly have an altered immune system response to stress.  This may increase their risk for mental and physical health problems.

In the study, stress led to significantly larger increases in a protein marker of inflammation in poor sleepers compared to good sleepers.   The protein, interleukin-6, is primarily produced at sites of inflammation.  It is a marker associated with poor health outcomes and even death.

“This study offers more evidence that better sleep not only can improve overall well-being but also may help prevent poor physiological and psychological outcomes associated with inflammation,” said Kathi L. Heffner, Ph.D., assistant professor of Psychiatry at the Rochester Medical Center and study leader.

The association between poor sleep and a heightened inflammatory response to acute stress could not be explained by other factors linked to immune impairment, including depression, loneliness and perceived stress, the researchers said in the study published by the American Journal of Geriatric Psychiatry.

“Our study suggests that, for healthy people, it all comes down to sleep and what poor sleep may be doing to our physiological stress response, our fight or flight response,” Heffner said.

The study, advertised as an investigation of stress and memory, involved 45 women and 38 men with an average age of 61 years. The participants were evaluated for cognitive status using a standard assessment. Each participant completed a self-report of sleep quality, perceived stress, loneliness and medication use. The participants had to be in good physical health to be in the study, but even so, about 27 percent of the participants were categorized as poor sleepers.

On the day of the study, the participants were given a series of tests of verbal and working memory, a battery of questions that served as the stressor. Blood was drawn before any testing began and then immediately following the testing and at three intervals spaced out over 60 minutes. The blood was studied for levels of interleukin-6, a protein primarily produced at sites of inflammation.

Poor sleepers reported more depressive symptoms, more loneliness and more global perceived stress relative to good sleepers. Poor sleepers did not differ from good sleepers when interleukin-6 was measured before the tests began. Across the group, the participants showed increases in interleukin-6. However, poor sleepers had a significantly larger increase in interleukin-6 in response to the stressful tests compared to good sleepers, as much as four times larger and at a level found to increase risk for illness and death in older adults.

A further analysis of the results for the impact of loneliness, depression or perceived stress on interleukin-6 levels found no association. Poor sleep stood as the predictor of elevated inflammation levels.

“We found no evidence that poor sleep made them deal poorly with a stressful situation. They did just as well on the tests as the good sleepers. We did not expect that,” Heffner said. “We did find that they were in a worse mood after the stressor than a good sleeper, but that change in mood did not predict the heightened inflammatory response.”

As people age, a gradual decline in the immune system occurs along with an increase in inflammation. Heightened inflammation increases the risk for cardiovascular disease, diabetes and other illnesses, as well as psychiatric problems.

While relatively little is known about the pathways through which poor sleep impacts circulating levels of inflammatory proteins, the study led by Heffner provides a clinical target for preventing poor outcomes for older adults.

“There are a lot of sleep problems among older adults,” Heffner said. “Older adults do not have to sleep poorly. We can intervene on sleep problems in older adulthood. Helping an elderly person become a better sleeper may reduce the risk of poor outcomes associated with inflammation.”

 

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Feb
25
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Earth’s exoplanet ‘siblings’ can be different

By Kevin Orrman-Rossiter | Filed in Physics, Space Science

The finding of numerous exoplants, planets outside of our own solar system or extra-solar planets, have made astrophysics once again a hot topic.  A week does not seem to go by without a new discovery of an exoplanet by NASA’s Hubble telescope.  At the same time intense activity is taking place to understand the nature of these exoplanets.

The interest from professionals and public is understandable.  this forms part of one of the ‘big’ questions; “Are we alone in the universe?”

Finding a variety of planetary systems enables scientist help test theories and models of planetary formation.  One such model looks at the stars of these planetary systems.

The study of the the abundance of elements in the photosphere of stars that host planets is the key to understanding how protoplanets form.  The photosphere is the visible surface of a star.  Since a star is a ball of hot gas this is not a solid surface but actually a layer about 100km thick (very thin compared to the 700,000km radius of the Sun).  It is found that the ratios of elemental abundance in the photosphere is a good indication of the chemistry of any planets that form around it.

It also helps to model which protoplanetary clouds evolve planets and which do not. These studies have important implications for models of giant planet formation and evolution.  They also help us to investigate the internal and atmospheric structure and composition of extrasolar planets.

An international team of researchers has discovered that the chemical structure of Earth-like planets can be very different from the bulk composition of Earth.

They have presented results of simulations of terrestrial planet formation.  Their results have looked at three extrasolar planetary systems.  These systems have photospheres with Mg/Si  values less than 1.0.

Theoretical studies suggest that carbon/silicon (C/O) and magnesium/silicon (Mg/Si), are the most important elemental ratios in determining the mineralogy of terrestrial planets.  The ratios can give us information about the composition of these planets. The C/O ratio controls the distribution of Si among carbide and oxide species, while Mg/Si gives information on the silicate mineralogy.

This resulting bulk chemical is expected to have a dramatic effect on the existence and formation of the biospheres and life on Earth-like planets.

The Earth’s upper mantle has an Mg/Si atomic ratio (1.27) which is also similar to Venus. These characteristics seem to predominate throughout the inner solar system.

During formation of the terrestrial planets, elements more volatile than silicon were depleted and may have been transported outwards to recondense in the lower-temperature environment of the outer asteroid belt. Some Si may also have been lost in this manner, although not enough to alter planetary Mg/Si ratios. However, recondensation of this Si on the relatively small mass of dust particles in the asteroid belt would have caused a substantial enrichment of Si relative to Mg.  It thus seems likely that it is the Mg/Si ratio of the inner planets ( ∼ 1.27), which is more representative of the solar nebula value.

An analogous process of radial chemical fractionation may also have occurred in the outer solar nebula, with volatile elements and silicon lost from the growing giant planets being recondensed onto cosmic interplanetary dust particles and cometary bodies further out from the Sun.

In 2010 the first numerical simulations of planet formation in which the chemical composition of the proto-planetary cloud was taken as an input parameter.  Terrestrial planets, rocky siblings of Earth, were found to form in all the simulations with a wide variety of chemical compositions.   So these planets might be very different from Earth.

A first detailed and uniform study of C, O, Mg and Si abundances was also carried out in 2010.  This was the first to determine the abundance of all of the required elements in a completely internally consistent manner, using high quality spectra and an identical approach for all stars and elements, for a large sample of both host and non-host stars.  This 2010 study looked at 100 stars with detected planets and 270 stars without detected planets.  The majority of this data came from from the homogeneous high-quality European Southern Observatory HARPS studies.

In 2009 the HARPS team announced the discovery of the lightest exoplanet so far, Gliese 581e.  As well as the first exoplanet, Gliese 581d, to exist in the habitable zone.  A zone around its host star where surface water could exist.

Mineralogical ratios quite different from those in the Sun were found.  Showing that there is a wide variety of planetary systems which are unlike the Solar System.  Many planetary-host stars had a Mg/Si value lower than 1.  Suggesting that their planets will have a high Si content to form species such as MgSiO3.  The amount of radioactive and some refractory elements (especially Si) can have important implications for planetary processes like plate tectonics, atmospheric composition and volcanism.

The latest numerical simulations have shown that a wide range of extrasolar terrestrial planet bulk compositions are likely to exist. Planets simulated as forming around stars with Mg/Si ratios less than 1 are found to be Mg-depleted (compared to Earth), consisting of silicate species such as pyroxene and various types of feldspars.

Planetary carbon abundances also vary in accordance with the host stars’ C/O ratio. The predicted abundances are in keeping with observations of polluted white dwarfs (expected to have accreted their inner planets during their previous red giant stage).

From these earlier studies the present authors believe there could be billions of Earth-like planets in the Universe but a great majority of them may have a totally different internal and atmospheric structure.

The observed variations in the key C/O and Mg/Si ratios for known planetary host stars implies that a wide variety of extrasolar terrestrial planet compositions are likely to exist, ranging from relatively “Earth-like” planets to those that are dominated by C, such as graphite and carbide phases (e.g. SiC, TiC).

The chemical and dynamical simulations were combined by assuming that each embryo retains the composition of its formation location and contributes the same composition to the simulated terrestrial planet. The innermost terrestrial planets located within approximately half the distance of Earth to the Sun (~0.5 AU from the host star) contain a significant amount of the refractory elements Al and Ca (~47% of the planetary mass).

Planets forming beyond half-earth distances from the host star contain steadily less Al and Ca with increasing distance. One planetary system, 55 Cnc, has a C/O ratio above 1 (C/O = 1.12). This system produced carbon-enriched “Earth-like” planets.  All of the terrestrial planets considered in this work have compositions dominated by O, Fe, Mg and Si, most of these elements being delivered in the form of silicates or metals (in the case of iron). However, important differences between those planets forming in systems with C/O < 0.8 (Iota Horologii, HD19994) and those with C/O > 0.8 (55Cnc) have been found.

These results highlight planets built in chemically non-solar environments (which are very common in the Universe) may lead to the formation of strange worlds, very different from the Earth!

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Feb
24
0

Anticipation of stressful events may cause cellular ageing

By Kevin Orrman-Rossiter | Filed in Neurobiology, Philosophy, Psychology, Social neuroscience

Psychologists have found people most threatened by the anticipation of stressful tasks looked older at the cellular level.  The ability to anticipate future events allows us to plan and exert control over our lives.  Anticipation may also contribute to stress-related increased risk for the diseases of aging, according to this study.

The researchers studied 50 women, about half of them caring for relatives with dementia.  The stress researchers were trying to examine the psychological process of how people respond to a stressful event and how that impacts their neurobiology and cellular health.

The researchers assessed cellular age by measuring telomeres, which are the protective caps on the ends of chromosomes.  Short telomeres index older cellular age and are associated with increased risk for a host of chronic diseases of aging, including cancer, heart disease and stroke.

Research on telomeres, and the enzyme that makes them, was pioneered in 1985, by three scientists who received the Nobel Prize in Physiology or Medicine in 2009 for their work.  Molecular biologist Elizabeth Blackburn, was one of these three, and is a co-author on this study.

The researchers also found evidence that caregivers anticipated more threat than non-caregivers when told that they would be asked to perform the same public speaking and math tasks. This tendency to anticipate more threat put them at increased risk for short telomeres.  Based on that, the researchers propose that higher levels of anticipated threat in daily life may promote cellular aging in chronically stressed individuals.

How you respond to a brief stressful experience in the laboratory may reveal a lot about how you respond to stressful experiences in your daily life.  These findings are preliminary for now, but they suggest that the major forms of stress in your life may influence how your respond to more minor forms of stress, such as losing your keys, getting stuck in traffic or leading a meeting at work.

The long term goal of this research is to gain better understanding of how psychological stress promotes biological aging.  Targeted interventions could then be designed to reduce risk for disease in stressed individuals.

The researchers do feel that they are making some strides toward understanding how chronic stress translates into the present moment.  We now have preliminary evidence that higher anticipatory threat perception may be one such mechanism.

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