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What clues about life in our solar system are encased in the millions of tonnes of meteorite that pummel our atmosphere every day? met astrobiologist Zita Martins at the Royal Society's Objects in Space exhibition to find out.

The two rocks in this room came from space and are 4.5 billion years old. They are meteorites which landed in the UK and are among the oldest objects anyone will ever stand next to.

The meteorites are on display at the Royal Society as part of a small exhibition called Objects in Space, which runs until the end of March. One of them, believed to be Britain's largest, weighs 90kg and is being shown to the general public for the first time.

People like Zita Martins can use meteorites to peer into the solar system's past. An astrobiologist at Imperial College London, Martins says meteorites are like time machines -- data locked up in rock, waiting to be processed. But impressive as the human-mass, billion-year old meteorite is, Martins says she's more interested in content than appearance.

"The meteorites I'm interested in are the stony ones, specifically carbonaceous chondrites," Martins says. "Those are the ones very rich in carbon, and I'm interested in them because they have lots of organic molecules."

Those organic molecules -- amino acids, nucleobases and carboxylic acids -- are the building blocks of life, and Martins says that meteorites may have brought some of these molecules to a young Earth during a period known as the "heavy bombardment".

"As scientists, we think that meteorites may have played a key role in the origins of life. We're not saying they brought life, that's a completely different theory. But building blocks for life were brought to earth by meteorites, that we know," she says.

Martins says she typically deals with milligrams of meteorite, not kilograms. Her samples come in the post. She crushes and cleans them, stripping away everything but the organic molecules she is interested in. When the organic molecules are isolated, she runs them through a process called gas chromatography-mass spectrometry (GC-MS) -- the same process used to detect explosives in airports. "Its basically a big oven. You warm the sample up and at a certain temperature the molecules enter the gas form. Then they go into a second bit of the machine which breaks them up into tiny pieces. I see the tiny pieces and try and put them back together -- it's like a puzzle."

Most meteorites are shards, leftovers from collisions between asteroids in the belt between Mars and Jupiter which were spat out towards Earth and captured by our gravity. But Martins says that we also have about 100 meteorites from Mars and the Moon, and that we know where those few came from because we have data from their source. "During the Viking mission in 1975, the rover analysed the Martian atmosphere. The rare gas composition of the atmosphere is exactly the same as we find in the Martian meteorites," she says. The Apollo missions brought Moon rocks back to Earth, and those match up with just a few meteorites that have been found.

A slice through of one of those Moon rocks is on the wall opposite the 90kg meteorite. It looks like an ancient, cracked pavement, seen in false colour. Martins walks over to it: "This is a thin section. You get a slice of meteorite and put it under the microscope, lit from behind. Depending which minerals you have you get different colours. This one is lunar soil. We have lunar meteorites, but this is lunar soil."

Next to the slice of Moon is a matrix of different-coloured dots painted by Damien Hirst. It's a larger version of the colour calibration cards used by Britain's failed Mars lander, Beagle 2, to ensure it saw the right colours. Zita exhales when I ask her about the potential of the Beagle mission. "Huge. It would have been huge if it worked. We've only ever had one life detection mission to any planet -- the Viking mission in the 70s."

Martins' meteorites are certainly fascinating -- although there are only 20 different sorts of amino acids on earth, she says that more than 80 have been found on meteorites. But there's no remote way to find out whether these are more just the byproducts of an extraterrestrial chemistry experiment. To know for sure, science will have to head back out into the solar system to gather more data.

The Objects in Space exhibition runs until 30 March

Image:  Allende / Jon Taylor / CC BY-SA 2.0


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    dre solo
    Mar 16th 2012

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