Question

If arqueobacteria are the first forms of life to look for on Mars, how do we propose to find and recognize them?

As you may already know, arqueobacteria are ancient anaerobic microbes. They can withstand extreme heat and oxygen deprivation; in fact, arqueobacteria are believed to be among the first organisms to survive the hostile atmosphere of the early Earth, one with little oxygen and plenty of carbon dioxide. Since the atmosphere of present-day Mars is replete with carbon dioxide (over 90%) some scientists believe that if any microbial life is to be found on Mars, it may bear some resemblance to arqueobacteria or other extremophilic bacteria here on Earth. For this reason, Mars-landed experiments (current and future) plan to investigate several aspects of the Martian surface for evidence of microbial life. For example, because of the connection between water and any plausible Martian biology, it will be of utmost importance to find out how much water is (and perhaps used to be) present on the surface. Methods such as X-ray and gamma-ray spectroscopy may inform us in this respect. Likewise, mass spectrometry may tell us how much biogenic elements (carbon, hydrogen, oxygen and nitrogen) may be present on the surface. Also, if life ever exerted a global geochemical effect on Mars like it did on Earth, we would expect to find its signature in the gases trapped in the polar ice caps. Lastly, since many scientists speculate that life could be hiding in the warmer subsurface, searching for possible life on Mars might also necessitate a drilled sample to be returned to Earth. While this only a short list of the tests NASA has in store for Mars, you can see the detailed summary of NASA’s Mars exobiology strategy at: http://cmex-www.arc.nasa.gov/MarsNews/mars_papers/Docs/mars_strat.html Anna Lee Strachan, NASA Astrobiology Institute
March 7, 2002