Are we looking for Martian life in all the wrong places?

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Mosaic of Mars created from over 100 images obtained by the Viking Orbiters in the 1970s(Credit: NASA)

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A new study suggests that we may be searching in the wrong place for signs of life on Mars, when we examine rocks excavated by meteor impacts for organic compounds. The research could allow space agencies to select landing sites for future missions that are more likely to yield samples containing the markers of ancient, or even present-day life.

When NASA searches for life on Mars, the search focuses on trying to detect tiny organic compounds, which are most likely to be discovered encased in Martian rock. However, compounds that may have existed in rocks located on the surface of Mars would have been degraded by radiation from the Sun.

Consequently, rocks that had been buried deep beneath the surface, and recently (at least in geological terms) brought to the surface by powerful meteor strikes, are considered prime targets for rovers such as Curiosity as they trundle along looking for signs of life.

The new study, undertaken by scientists from Imperial College London and the University of Edinburgh, aimed to test whether biological compounds encased in Martian rock could survive the extreme conditions created in the aftermath of a meteor strike.

Impact craters such as the one pictured above have the capacity to excavate rocks that would ordinarily be inaccessible to Mars exploration missions(Credit: NASA/JPL-Caltech/Univ. of Arizona)

The team placed various organic compounds contained in an analogue of Martian rock inside a piston cylinder device, and subjected them to the temperature and pressure that would be exerted on the sample, if it were to be ejected by the impact of a 10-m (33-ft) meteor impact.

Following chemical analysis of the samples, it was discovered that a meteor strike of this magnitude would destroy certain types of organic compounds, but that others would survive. Traces of long chain hydrocarbon dominated-matter, which comprises algal and microbial life, were degraded to the extent that they were undetectable. However, organic compounds known as aromatic hydrocarbons, which are found in plant life, survived the tests relatively unscathed.

The knowledge that meteor impacts have the capacity to erase the hallmarks of life that may once have been contained in excavated rocks could aide space agencies when selecting the landing sites for future missions to the Red Planet. Further research may identify certain families of impact sites best suited to discovering clues to life on Mars, and which ones to avoid.

Moving forward, the team intends to test a wider range of impact intensities in order to determine the extent to which the size of the meteor, the angle at which it struck, and the depth at which the sample is buried has an effect on an organic compound's ability to survive an impact.

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