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Updated 10:00 AM August 14, 2006




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Mars' surface probably can't support life

The question of whether the planet Mars can support life has entranced lay people and scientists for years. New research suggests that dust devils and storms on the Red Planet produce oxidants that would render its surface uninhabitable for life as we know it.
This view of Mars, the sharpest photo ever taken from Earth, reveals small craters and other surface markings only about a dozen miles (a few tens of kilometers) across. The black diagonal section of missing data at about the eight o'clock position is a part of the ACS camera's coronograph, which is designed to block light from bright stars so that fainter objects near the stars can be studied. (Photo courtesy NASA, J. Bell (Cornell U.), and M. Wolff (Space Science Inst.))

"As a consequence, any nascent life (microorganisms, for example) or even prebiotic molecules would find it hard to get a foothold on the surface of Mars, as the organic material would be scavenged efficiently by the surface oxidants," says Sushil Atreya, professor in the Department of Atmospheric Oceanic and Space Sciences (AOSS).

The results also explain inconsistencies in earlier space experiments that sought to determine if Mars had once or currently supports life. Mars is thought to have been created with the same ingredients that on Earth led to the formation of molecules associated with life. Yet, organic molecules never have been detected on Mars' surface, Atreya says.

Atreya is lead author on one of two papers published last month in the journal Astrobiology that discuss the findings. Atreya's paper is called, "Oxidant Enhancement in Martian Dust Devils and Storms: Implications for Life and Habitability."

The research was conducted by the AOSS, the Goddard Space Flight Center of NASA and the University of California, Berkley, with several other universities and institutes participating.

The first Astrobiology paper calculated the excess carbon monoxide, hydroxyl and eventually hydrogen atoms produced when electric fields generated by dust devils and storms cause carbon dioxide and water molecules to split. Hydrogen and hydroxyl have been known to play a key role in the production of hydrogen peroxide in the Martian atmosphere.

Gregory Delory, senior fellow at the Space Sciences Laboratory at UCLA, Berkeley, is first author of that paper, with co-authors Atreya and William Farrell of Goddard Space Flight Center, in Greenbelt, Md. The paper is called "Oxidant Enhancement in Martian Dust Devils and Storms: Storm Electric Fields and Electron Dissociative Attachment."

Atreya's team calculated that the amounts of hydrogen peroxide produced during these reactions would be large enough to result in its condensation—essentially hydrogen peroxide would snow from the sky and contaminate the planet when it fell.

Atreya's paper suggests that the hydrogen peroxide would scavenge organic material from Mars, and it could also accelerate the loss of methane on the planet, requiring a larger source to explain the recent detection of this gas on Mars. "Methane is a metabolic byproduct of life as we know it, but presence of methane does not by itself imply existence of life on a planet," Atreya says.

Scientists regard Mars as Earth's closest relative. "Of all the planets in the solar system, Mars resembles the Earth most. And outside of the Earth, it has the best chance of being habitable now or in the past when the planet may have been warmer and wetter," Atreya says. Presence of life below the surface of Mars at any time is not ruled out by this research.

The research also helps explain contradictory results in a series of experiments in 1970s that suggested microscopic life might have been present in Martian soil. Called the Viking Project, the primary objective was to determine if there was life—past or present—on Mars. Biological experiments conducted by the two landing units, Viking 1 and 2, yielded conflicting results.

In addition to lead authors Atreya and Delory, co-authors of both papers are Farrell, and Nilton Renno and Ah-San Wong (U-M), Steven Cummer (Duke University), Davis Sentman (University of Alaska), John Marshall (SETI Institute), Scot Rafkin (Southwest Research Institute) and David Catling (University of Washington).

The research was funded by NASA's Mars Fundamental Research Program and NASA Goddard internal institutional funds.

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