Back to dust
Astronomers get first glimpse of the stuff that made the solar system
Dust kidnapped by astronomers from a comet, dating back to the origin of the solar system, has just arrived to the UK.
Scientists are hopeful that the study of the 4.5 billion year-old material will give answers to the longstanding questions of how the Earth formed and how life first appeared.
"This weekend was the most exciting weekend for 30 years for planetary scientists. It is the first time since the Apollo missions that samples of rock have been returned from space to Earth. The thousandth of a gram of dust collected from comet Wild-2 will probably tell us more about the formation of the Solar System than the last 100 years of telescope observations of these objects. It is a great time to be into dust," said Dr Genge, an expert on extraterrestrial dust at Imperial.
The samples from the comet Wild2 consist of millions of microparticles that were captured from the comet's tail of dust by the NASA space satellite Stardust.
Comets are amongst the most primitive objects in the solar system, and their composition has not changed ever since the beginning of the universe.
The composition of the comet's dust should therefore tell astronomers which chemical ingredients made up the primordial solar nebulae from which planets formed.
Astronomers will also be looking at whether comets have organic composts that could have seeded terrestrial life.
This is the first time that particle samples from comets return to the Earth nearly unchanged.
The satellite Stardust collected these samples when it briefly tail chased the comet Wild-2 in its sunbound journey from the Kuiper Belt, the frontier region of the Solar system.
When the comet approached the inner part of our solar system, incoming solar radiation slowly started melting and evaporating part of the comet's icy surface.
The otherwise quiet and icy comet became one of the most active surfaces in the solar system, jetting gas and donning a tail of ejected dust.
Stardust was there to capture some of these ejections, bringing home millions of particles for careful scrutiny. It also took 72 pictures of the 5-kilometre "flying mountain" of ice, rock, and gas, giving astronomers the first ever close-up view of a comet.
The satellite's "sample return canister" landed on 15 January in the desert of Utah in "excellent" condition. Parcels with its contents were shipped all over the world for analysis.
Space scientists at Imperial College, the Natural History Museum, and the Open University in the UK were amongst the happy recipients of 4.5 billion year-old dust specks.
The dust came trapped in blocks of "aerogel", an extremely light type of foam that can capture the tiny particles without damaging them.
"Receiving these samples is like being the first man on the Moon, only without the space suits," Dr Genge commented.
"It's enormously exciting to be one of the first people to examine these tiny dust grains from a comet."
Although the dust specks are less than a 10-millionth of a metre in size, astronomers will be able to tell which minerals compose them by using X-ray scans and electron microscopes.
The analysis will take months or even years, but may provide fasttrack answers to questions that last for centuries:
"Did comets seed the Earth with water for the oceans and the organics to make living things? What were the basic interstellar building blocks of planets and how were these assembled 4.5 billion years ago? "
Watch this space: an interview with Dr Genge will follow in one of the next issues.
