By J. M. Sinclair

Does life really exist on Mars? It almost seems like about once every decade, some group of scientists comes up with unequivocal proof that it does, at least in a microbial form, only to be shot down a few months later by another group of scientists during peer review. We still don't know the answer, but the claims from scientists are accelerating and moving in favor of microbial life existing on a planet that just a few years ago was thought to be completely dead.

19th century theories

The controversy begins in 1854, when Trinity College, Cambrige fellow William Whewell formulated a theory that Mars may have oceans and land, and even life. In 1877, Giovanni Schiaparelli thought he observed canals on Mars, followed by others, culminating in Percival Lowell's claims that the canals were irrigation canals created by an advanced civilization. This set the stage for H.G. Wells, and Orson Welles, to scare the dickens out of the world with fictional accounts of Martians attacking the earth. The canals turned out to not exist at all, having been artifacts created by the imprecise optics of their telescopes, and the water and continents were long gone.

The space age

In 1976 NASA's Viking landers became the first human made objects to survive the descent to the surface of Mars and begin taking measurements and photographs. The spacecraft were equipped with life detecting experiments that included four experiments. The first two experiments gave negative results, but the third experiment did not. Designed to inject nutrients into the Martian soil and see if anything ate it, the experiment showed that something did indeed eat and metabolize the material. The fourth experiment  was also negative. So what made the third experiment show a positive result, and the others a negative? Scientists ultimately concluded that it was a chemical reaction due to some strange 'superoxidant' that could react directly with water. This does not happen on earth, due to the presence of humidity. The nature of this hyperoxidant has never been explained, nor has the effect been reproduced exactly as it was on Mars in the laboratory, however similar experiments with other chemicals seem to suggest that it could happen. One of the designers of the experiments, Gilbert Levin, countered that there may have been bacteria detected by the instruments, but that they were so few in number that only one experiment was capable of seeing them. In any case, the debate rages on.

A stone's throw from the Martian surface

Even more compelling research was released in 1996 by another group of NASA scientists. Examining a meteorite named ALH84001, the scientists determined that microscopic images seemed to show tiny primitive fossilized bacteria. In addition, organic particles were found in abundance. While not automatically indicative of life, these particles, known as PAHs were different from those normally found in meteorites. Icing the cake were the discovery of tiny clumps of minerals that look very similar to those created by bacteria on earth, with the variety and distribution over such a small area making it unlikely that anything other than a bacteria could have created them. Chemical analysis of the meteorite itself showed that it had to have originated on Mars, with no other candidates in the solar system coming close to the chemistry seen in this rock, which is identical to that of the chemistry of rocks on Mars. Tiny bubbles found in the meteorite contained gas that was identical to the Martian atmosphere as measured by Viking, and the meteorites even show evidence of shock created when the meteorites were ejected from Mars by the impact of an asteroid.

As is typical of the debate regarding Martian life, the fossil findings have been surrounded by a great deal of doubt and controversy from the scientific community. The evidence put forth by the NASA team has yet to be accepted as fact. In 2004, a European team confirmed earlier observations that methane exists in the Martian atmosphere. What's interesting here is that methane can't last very long in that planet's atmosphere without being broken down, so the gas had to be replenished by some process on Mars. There are only three things that can do it, Life, Volcanos and a strange reaction called 'Serpentinization'. Most current theories seem to suggest that Mars is volcanically dead, though recent evidence may suggest otherwise. Serpentinzation itself is odd, because the process requires liquid water, where the mineral olivine is converted into serpentine. This may happen below the surface of Mars, but if it is the case, it would prove that liquid water exists somewhere below the surface of Mars. Liquid water may mean life. The last option is that life itself creates the methane. Whichever is the case, the mechanism of methane generation on Mars will be extremely important to furthing our knowledge of Mars.

Hydrogen Peroxide?

Now the controversy heats up again. A new claim by Joop Houtkooper at the University of Geissen in Germany suggests that a bizarre form of bacteria exists that survives the extreme temperatures on Mars by filling its cells with a mixture of water and hydrogen peroxide, creating a sort of anti-freeze. A common chemical used on earth to kill bacteria, hydrogen peroxide may just allow these tiny creatures to thrive on mars. Houtkooper even goes so far as to suggest that 0.1 percent of Mar's soil is biological in origin, and that the creatures exist by using the perioxide to gather minute amounts of water from the planet's atmosphere. When exposed to too much water, the creatures would overhydrate and die, producing the results seen by the experiments on Viking.

Biological use of hydrogen peroxide is not unknown on earth. Certain types of beetle use a solution of peroxide and water to deter predators with a jet of steam. The problem with peroxide is that it is also generally deadly to bacteria, leading to its anti-septic properties. Just a few days after the release of Houtkooper's research, the controversy is already raging with a number of scientists coming out against the paper, and calling into question the credibility of the researchers.

A new chance at detecting life

In 2008, NASA's Phoenix Lander will touch down on on the cold polar region of Mars. Onboard the craft is an experiment that will drill into the surface of mars, and try to find a zone of habitability where bacteria could exist. While this experiment probably won't settle the question, it will tell us if the upper soils of Mars can support bacterial life, adding more fuel to the fire in the century old debate on whether life exists on Mars. The pendulum continues to swing back and forth on the question, but with so many claims now being debated, it seems almost likely that microbial life does exist on Mars. Perhaps they aren't anywhere near the surface, and exist deep below the harsh atompshere, but never the less Mars continues to be the most likely candidate in our solar system, other than the earth, where life may be found.

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