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Are we all Martians?

Many planetary scientists say it’s conceivable that all life on Earth is descended from organisms that originated on Mars and were carried here aboard meteorites.

india Updated: Mar 24, 2011 14:31 IST

Many planetary scientists say it’s conceivable that all life on Earth is descended from organisms that originated on Mars and were carried here aboard meteorites.

And if that’s the case, an instrument being developed by researchers at MIT and Harvard could provide the clinching evidence.

In order to detect signs of past or present life on Mars - if it is in fact true that we’re related - then a promising strategy would be to search for DNA or RNA, and specifically for particular sequences of these molecules that are nearly universal in all forms of terrestrial life.

That’s the strategy being pursued by MIT research scientist Christopher Carr and postdoctoral associate Clarissa Lui, working with Maria Zuber, head of MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS), and Gary Ruvkun, a molecular biologist at the Massachusetts General Hospital and Harvard University, who came up with the instrument concept and put together the initial team.

Lui presented a summary of their proposed instrument, called the Search for Extra-Terrestrial Genomes (SETG), at the IEEE Aerospace Conference this month in Big Sky, Montana.

The idea is based on several facts that have now been well established. First, in the early days of the solar system, the climates on Mars and the Earth were much more similar than they are now, so life that took hold on one planet could presumably have survived on the other.

Second, an estimated one billion tons of rock have traveled from Mars to Earth, blasted loose by asteroid impacts and then traveling through interplanetary space before striking Earth’s surface.

Third, microbes have been shown to be capable of surviving the initial shock of such an impact, and there is some evidence they could also survive the thousands of years of transit through space before arriving at another planet.

So the various steps needed for life to have started on one planet and spread to another are all plausible. Additionally, orbital dynamics show that it’s about 100 times easier for rocks to travel from Mars to Earth than the other way. So if life got started there first, microbes could have been carried here and we might all be its descendants.

If we are descendants from Mars, there might be important lessons to be learned about our own biological origins by studying biochemistry on our neighbor planet, where biological traces erased long ago here on Earth might have been preserved in the Martian deep freeze.

The MIT researchers’ device would take samples of Martian soil and isolate any living microbes that might be present, or microbial remnants (which can be preserved for about up to a million years and still contain viable DNA), and separate out the genetic material in order to use standard biochemical techniques to analyze their genetic sequences.

“It’s a long shot,” Carr concedes, “but if we go to Mars and find life that’s related to us, we could have originated on Mars. Or if it started here, it could have been transferred to Mars.” Either way, “we could be related to life on Mars. So we should at least be looking for life on Mars that’s related to us.”