5 November 2008

Moon craters may hold traces of early life

Cosmos Online
Ice deposits hidden in the Moon's darkest craters might contain traces of early life from meteorites blasted off the Earth by asteroids billions of years ago.
The Moon's south pole

Remains of ancient life?: The Shackleton Crater (dark patch in centre) lies at the Moon's south pole. While its rim is exposed to near continual sunlight, the interior is perpetually shaded. The image comes from NASA's Clementine space probe. Credit: NASA

LONDON: Ice deposits hidden in the Moon’s darkest craters might contain traces of early life from meteorites blasted off the Earth by asteroids billions of years ago.

These remains could reveal clues about the origin and evolution of life on Earth or even contain remnants of life from other planets in the Solar System, such as Mars, said astrobiologist Joop Houtkooper, of the University of Giessen in Germany.

“The long-existing knowledge about the Moon’s rotation axis implies that there are places in eternal shadow at the Moon’s poles,” he told Cosmos Online. “That means exceptionally low temperatures at, and some depth below, the surface there. Ice deposits have been inferred from observations by satellites around the Moon and by radar from Earth.”

“Doubly dark spots”

The dark spots are ‘craters-within-craters’ that are never exposed to sunlight, making them a chilly -248ºC. They are therefore ideal for freezing water and gases such as nitrogen, carbon dioxide or methane, and preserving traces of life undisturbed by sunlight and solar winds.

The best bet for finding evidence of life is within the Shackleton Crater at the Moon’s south pole, said Houtkooper, who presented his idea at the 2008 European Planetary Science Congress in Germany.

This evidence could come in the form of organic molecules, fossil remains, dead organisms, or even organisms in a dormant state that could be revived, such as bacterial spores, he said.

It is even possible that microbes could have survived for a short while after impact, argued Houtkooper. Although there is no atmosphere to support life today, a temporary, thin atmosphere could have formed shortly after an impact event, as water and gases from the space rock vaporised, he claimed.

Indian Moon probe

Experts have described the theory as possible, but a long shot.

“The microbial system on Earth extends to a depth of several kilometres into the crust, and so rocks blasted off the Earth by asteroid impacts could well have contained microbes,” said astrobiologist Malcolm Walter from the University of New South Wales in Sydney.

“I’d be very conservative about this idea [though],” said Lewis Dartnell, an astrobiologist at University College London (UCL) in the United Kingdom. “If, say, a comet landed right in the middle of a crater, then it’s possible”.

While Houtkooper agreed the idea is controversial, he maintains that there’s a good chance that remains of life could be found – and the proof may not be far away. India’s Chandrayaan-1 space probe launched in October is tasked specifically with looking for ice deposits at the lunar poles.


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