Did life on Earth begin on Mars?

US scientists are planning an experiment for a future mission to Mars – to find out if we are all Martians. They want to test the theory that life began on the Red Planet and was then carried as simple bugs to Earth.

Mars pictured with the Hubble space telescope

Mars pictured with the Hubble space telescope (NASA/ESA)

The scientists are designing a testing kit to search for DNA and similar evidence that would identify any organisms on Mars.

Planetary scientists know that the climates on Earth and Mars were more similar in the solar system’s distant past. In fact Mars was probably more friendly for life early on as the planet is further from the Sun and would have cooled down first when it formed. They know that there was plenty of water on Mars and that oceans once covered much of the planet.

They also know that chunks of Mars have been blasted from its surface by asteroid impacts and later fallen to Earth as meteorites. There have been claims that some of these space rocks contain microbial fossils, though there is still hot debate.

It is possible for bits of Earth to reach Mars as meteorites too, but the nature of orbital dynamics means it is about a hundred times easier for martian rocks to reach us. It is estimated that a billion tons of Mars has reached Earth thanks to asteroid impacts.

In January 2009, NASA revealed that plumes of methane had been detected on Mars which could have a biological origin.

The new US experiment plans to look for microbes in martian soil, whether alive or preserved in the martian deep freeze. It will then separate out genetic material and analyse it.

The technique, called the Search for Extra-Terrestrial Genomes (SETG) has been designed by Christopher Carr, Clarissa Lui and Maria Zuber of Massachusetts Institute of Technology and Gary Ruvkun, a molecular biologist at the Massachusetts General Hospital and Harvard University.

Dr Carr said: “It’s a long shot, 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.

“We could be related to life on Mars so we should at least be looking for life on Mars that’s related to us.”

The experiment will also be able to tell if any bugs found on Mars are infectious and so might present a hazard to astronauts or if brought back to Earth in rock samples.

The team expect to spend two years developing their instrument before it is ready to be sent to Mars on a NASA probe.

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