Tuesday, February 27, 2001

Finding Evidence of Life in the Solar System

by Maryann Ashworth and Amanda O’Connor

Why would we want to build an instrument that can detect traces of life on other planets? An “in situ” instrument has numerous advantages. The most important being that we know we can analyze a sample that is brought back from outer space.  This extremely cautious procedure presents many problems.  The most important being whether or not the sample will actually be in good condition to analyze. There have been two major crashes of Mars explorations in the last five years leading to the belief that “in situ” would pose no difficulty.  We are guaranteed that the sample can at least be analyzed by stabilizing its condition from the first impact. Since it is more feasible to analyze the sample “in situ,” Dr. Fogel began to think about how to build such an instrument.
Obviously, the first step in building an instrument that can determine if there is life on another planet begins right here on Earth. Earth environments such as hydrothermal springs and vents are homes for Archae. It has been hypothesized that the creation of Archae and Eubacteria were most likely how life started on Earth.  This is also a clue as to how life could have been started or is started on other planets.  Scientists can also use current-day landscapes to scientifically work backwards. Dr Fogel discussed taking a modern environment and analyzing the relationships within that environment that have survived geologic time to indicate the time period when there were first signs of life.
Scientific data such as chemical clues that exist as biochemical remains and inorganic remains were discussed. Biochemical remains range from large molecules (living cells) to isotopic patterns formed by living organisms.  One important fact was that organic remains are present as biominerals (calcium carbonate, for example) or gases such as oxygen and methane that are produced in quantity solely by living organisms.
The next question that was posed was if biosignatures survive the geologic record. If they do not, then what does and how would we recognize it? Dr. Fogel performed a number of experiments observing the rate of carbon and nitrogen decay and concluded that bacterial signatures overprinted plant signatures. Fortunately, the microbial record will survive.