The discovery of water, possible fossils, organic compounds and a re-examination of the Viking 1 and 2 Labeled Release (LR) life detection experiments indicate that the probability of past and present Martian life is more than possible. In fact, per Gilbert V. Levin, Ph. D., creator of the 1976 Viking LR life detection experiments, the results conclusively show "microbial life exists in the top layer of the Martian surface."[1]
Beginning in 1976, a number of experiments aimed at detecting life were performed on board the Viking Landers. It was performed nine times (four times on Viking 1 and five times on Viking 2, with the landers being 4000 miles apart)
Strong positive results were found in all nine tests. When the radiolabeled 14C nutrient solution was injected into the Martian soil, the evolution of radiolabeled gas, likely Carbon Dioxide (CO2), consistent with biological metabolism was detected. Since then it has been proven that water, an essential ingredient for life, lies beneath the Martian surface, a terrain dominated by ice, and can be found in the Martian soil. On July 31, 2008 lab tests conducted aboard NASA's Phoenix Mars Lander detected the presence of liquid water in a sample of soil taken from a two inches deep trench. The argument for life on Mars was further advanced in 2001 when Hungarian scientists Tibor Ganti, Eors Szathmary, and Andras Horvath claimed to have discovered evidence of living organisms on Mars after analyzing 60,000+ photographs taken by the Mars Global Surveyor (MGS) probe. The pair stated that the spots were likely organisms living under the Martian icy surface
"These spots indicate that on the surface below the ice there are such organisms which, absorbing solar energy, are able to melt the ice and create conditions of life for themselves," Ganti told Reuters. "During the harsh Martian winters, when temperatures plummet to minus-328 Fahrenheit, these so-called Mars Surface Organisms are protected by a thick blanket of ice which then melts as the planet's early summer temperatures climb to just above zero. This repeat action, the team asserts, strengthens their suggestion of fixed, biological causes of spot formations" strongly suggesting "the life cycle of some kind of plant life
Phil Christensen of Arizona State University dismissed this premise. Instead, he attributed the cause to jets of Carbon Dioxide (CO2) bursting from the planet's polar cap as the Martian climate warmed each spring resulting dust and sand to fall to the surface in large splotches.
Nevertheless, Viking Lander cameras also appeared to show the presence of life. Also in 2005, two NASA scientists - Carol Stoker and Larry Lemke - made a case for the existence of Martian life during a presentation. The discovery of sulfate jarosite (a mineral found in terrestrial hot springs and acidic water bodies known to harbor life) and other salt minerals by Opportunity at Merdani Planum, an area believed to have once been submerged under water further bolstered their belief that Martian life could exist in underground ecosystems consisting of standing water
Additional evidence supporting the theory of present-day Martian life is the presence of desert varnish or coatings on some of the planet's rocks that are similar to compounds secreted by terrestrial microorganisms
Based on recent discoveries of extremophiles that thrive in the most inhospitable environments on Earth, a re-examination of the LR experiments, photographic evidence of possible present day Martian life forms, the presence of liquid water on Earth's neighbor, the existence of biological byproduct gases in the planet's thin atmosphere, and the likely existence of Martian fossils, it appears that the Earth may not be the only planet that harbors living organisms
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