Nasa 'missed' life on Mars

Nasa is to send a new rover to Mars

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Two Nasa space probes that visited Mars 30 years ago may have stumbled upon alien microbes on the Red Planet and inadvertently killed them, a scientist claims.

The problem was the Viking space probes of 1976-77 were looking for the wrong kind of life and did not recognise it, the researcher said in a paper presented at a meeting of the American Astronomical Society in Seattle.

The new report, based on a more expansive view of where life can take root, may have Nasa looking for a different type of Martian life form when its next Mars spacecraft is launched later this year, one of the space agency's top scientists said.

Last month, scientists excitedly reported that new photographs of Mars showed geological changes that suggest water occasionally flowed on the planet - the most tantalising sign that Mars is hospitable to life.

In the '70s, the Viking mission found no signs of life. But it was looking for Earth-like life, in which salt water is the internal liquid of living cells. Given the cold dry conditions of Mars, that life could have evolved on Mars with the key internal fluid consisting of a mix of water and hydrogen peroxide, said Dirk Schulze-Mach, author of the new research.

That's because a water-hydrogen peroxide mix stays liquid at very low temperatures (-68°F/-55.56°C ), does not destroy cells when it freezes, and can suck scarce water vapour out of the air.

The Viking experiments of the '70s would not have noticed alien hydrogen peroxide-based life and, in fact, would have killed it by drowning and overheating the microbes, said Schulze-Makuch, a geology professor at Washington State University.

One Viking experiment seeking life on Mars poured water on soil. That would have essentially drowned hydrogen peroxide-based life, Schulze-Makuch said. A different experiment heated the soil to see if something would happen, but that would have baked Martian microbes, he said.

"The problem was that they didn't have any clue about the environment on Mars at that time,'' Schulze-Makuch said. "This kind of adaptation makes sense from a biochemical viewpoint.''