Have we descended from Mars?

Boston: A team of researchers at Harvard and the Massachusetts
Institute of Technology are developing a device that will study
whether life on Earth descended from organisms that were originated on
Mars and carried to our planet aboard meteorites - a theory that would
make all humans of Martian-descent.

MIT research scientist Christopher Carr, postdoctoral associate
Clarissa Lui, head of MIT's Department of Earth, Atmospheric and
Planetary Sciences Maria Zuber and Harvard University molecular
biologist Gary Ruvkuna are working on the proposed instrument called
the 'Search for Extra-Terrestrial Genomes' (SETG).

The MIT researchers' device, which could be carried on future missions
to Mars, 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.

They would separate out the genetic material in order to use standard
biochemical techniques to analyse their genetic sequences. The team
would search for DNA or RNA in the Martian soil, separating any
possible organisms using the same techniques used for forensic DNA
testing on Earth.

Biochemical markers would be used to search for signs of particular,
genetic sequences that are nearly universal among all known life
forms.

SETG would take a sample of Martian soil from below the surface on
Mars, dredged up by a rover equipped with a deep drill.

"It is a long shot," Carr said in a MIT statement. "But if we go to
Mars and find life that is 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 is related to us."

Orbital dynamics show that it is about 100 times easier for rocks to
travel from Mars to Earth than the other way. If life got started on
Mars 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 neighbour planet, where biological traces erased long ago on
Earth might have been preserved in the Martian deep freeze," the
statement said.

The researchers estimate that it could take two more years to complete
the design and testing of a prototype SETG device.

A future mission with a lander or rover equipped with a drill could
potentially carry this life-detection instrument. The team is basing
its idea on several well-established facts.

In the early days of the solar system, the climates on Mars and Earth
were much more similar than they are now, so life that took hold on
one planet could presumably have survived on the other.

Further, an estimated one billion tons of rock have travelled from
Mars to Earth, blasted loose by asteroid impacts and then travelling
through interplanetary space before striking Earth's surface.

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," the MIT statement said.

Recent Mars orbiter and rover missions have shown that Mars once had
abundant water and many of the conditions thought to be needed to
support life.

While the surface of Mars today is too cold and dry to support known
life forms, there is evidence that liquid water may exist not far
below the surface.

"On Mars today, the best place to look for life is in the subsurface,"
Carr added.