Skip to main content

Stardust in Oxford

It is often said we are all made from stardust. Meteorites, such as those in the museum in Oxford, contain a remarkable ‘fingerprint’. The imprint of a time before our solar system was formed. Grains of stardust you can look at under a microscope; micron-sized grains of silicon carbide a billion years older than our solar system, spewed out from supernovae and giant stars, now trapped in the meteorites that were formed by the accretion of debris in the early development of our solar system.

But how can we be so certain of the origin and formation of these grains of dust? This is just one of the exciting questions discussed with Professor Alex Halliday when interviewed by Denis Noble for Voices from Oxford. Alex Halliday specializes in the chemistry of the planets, and is also the head of one the largest Divisions at the University of Oxford: Mathematical, Physical and Life Sciences. He studies the isotope nature of the composition of the earth and its evolution.

The unique properties of radio isotopes enable us to “trace the geological components and to determine where they came from and when they were formed.” They provide a unique view of the history of the universe and our solar system. A history locked in bits of rock.

We can use isotope properties in a variety of ways, Professor Halliday explains. The first of these is dating. Some radio isotopes with very long half lives are decaying over billions of years; others have very short half lives. A very sophisticated set of techniques have now been developed and modern mass spectrometry “has driven the science forward and opened up new opportunities”.

But it isn’t a fingerprint of time alone. Atomic masses of isotopes “will result in slightly different behaviour in natural processes” and by measuring the amount of one isotope over another “you can say something about temperature in the past.” It was the Nobel Prize winner, Harold Urey, who discovered the isotope deuterium, but who also was first to discover you could use the behaviour of isotopes to say something about the temperature of the oceans in the past.

Using this “forensic fingerprinting” with the properties of isotopes, Professor Halliday explains, we can also trace the source of components and where they came from, and this has produced some unexpected results. It was assumed that things were fairly well mixed up in the solar system because meteorites from the asteroid belt and from mars had roughly the same composition as samples from earth. But it was discovered about 20 years ago that there was something peculiar in the isotopic make­­ up of these meteorites. There were “some funny noble gas isotopic compositions.”

If you did selective leaching of them, gradually dissolving the entire meteorite, you are left with a few grains that were “unlike anything found on earth”. Thousands of these grains have been analysed with high precision for their isotopic composition and they are not normally found on the earth’s surface. They are fragments of dust, grains of silicon carbide, from other stars, that were brought into this solar system 4.5 billion years ago before it formed. These meteorites provide an amazing new archive for understanding how stars work. By using spectroscopy on stars we analyse their chemistry. But as Professor Halliday puts it “now we have samples of stars which is mind blowing.”


Ray Noble is News Editor for Voices from Oxford

Comments

Popular posts from this blog

Ian Duncan-Smith says he wants to make those on benefits 'better people'!

By any account, the government's austerity strategy is utilitarian. It justifies its approach by the presumed potential ends. It's objective is to cut the deficit, but it has also adopted another objective which is specifically targeted. It seeks to drive people off benefits and 'back to work'.  The two together are toxic to the poorest in society. Those least able to cope are the most affected by the cuts in benefits and the loss of services. It is the coupling of these two strategic aims that make their policies ethically questionable. For, by combining the two, slashing the value of benefits to make budget savings while also changing the benefits system, the highest burden falls on a specific group, those dependent on benefits. For the greater good of the majority, a minority group, those on benefits, are being sacrificed; sacrificed on the altar of austerity. And they are being sacrificed in part so that others may be spared. Utilitarian ethics considers the ba

The secret life of Giant Pandas

Giant pandas, Ailuropoda melanoleuca , have usually been regarded as solitary creatures, coming together only to mate; but recent studies have begun to reveal a secret social life for these enigmatic bears.  GPS tracking shows they cross each others path more often than previously thought, and spend time together.  What we don't know is what they are doing when together.  Photo by  Sid Balachandran  on  Unsplash For such large mammals, pandas have relatively small home ranges. Perhaps this is no surprise. Pandas feed almost exclusively on bamboo. The only real threat to pandas has come from humans. No wonder then that the panda is the symbol of the WWF.  Pandas communicate with one another through vocalization and scent marking. They spray urine, claw tree trunks and rub against objects to mark their paths, yet they do not appear to be territorial as individuals.  Pandas are 99% vegetarian, but, oddly, their digestive system is more typical of a carnivore. For the 1% of their diet

Work Capability Assessments cause suffering for the mentally ill

People suffering from mental health problems are often the most vulnerable when seeking help. Mental health can have a major impact on work, housing, relationships and finances. The Work Capability Assessments (WCA) thus present a particular challenge to those suffering mental illness.  The mentally ill also are often the least able to present their case. Staff involved in assessments lack sufficient expertise or training to understand mental health issues and how they affect capability. Because of  concerns that Work Capability Assessments will have a particularly detrimental effect on the mentally ill,  an  e-petition  on the government web site calls on the Department of Work and Pensions to exclude people with complex mental health problems such as paranoid schizophrenia and personality disorders. Problems with the WCA  have been highlighted in general by the fact that up to 78% of 'fit to work' decisions are  being overturned on appeal. It is all to the good that they