Though we can't yet be certain, the evidence is mounting that Mars could support primitive life. Are we alone in the universe, or is there other life out there? It is a question that the we have always struggled to answer. As our technological prowess has grown, simple wonder has given way to scientific examination of the possibilities. In 1896, Nikola Tesla posited that radio could be used to communicate with extraterrestrial life, and in 1899 he recorded cosmic radio waves. In 1961, Dr. Frank Drake from essayup formulated an equation to mathematically predict the number of intelligent civilizations sufficiently advanced to communicate across interstellar space. Various Search for Extra-Terrestrial Intelligence, or SETI, programs have been ongoing ever since, listening for any sign of intelligent life. And despite the lack of intelligent transmissions from elsewhere in our own solar system, many scientists think that there are several promising places to look for more primitive life, including our neighboring planet Mars. The Red Planet Mars has long held a special place in our quest for other life. In the 19th century, astronomers believed they saw a network of channels on Mars, leading amateur astronomer Percival Lowell to speculate that these were the remains of a long dead civilization. Later observations using better telescopes proved that these channels did not exist, and the first flyby of Mars by the spacecraft Mariner 4 showed the surface of Mars to be barren and desert-like. In the late 1970s, the Viking spacecraft landed on Mars and carried out experiments to look for signs of microscopic life in the soil of Mars, but the results were inconclusive. One of the experiments produced results that could have been consistent with microbes in the soil, but the scientific consensus was that the results were easily explained by the presence of a strong oxidant is in the soil. The oxidant would react with the water added to the soil in the experiment, mimicking a possible result if a microorganism were present. The Meteorite Then, in 1996, a team of NASA scientists studying a meteorite of Martian origin designated ALH84001 published a paper indicating that the meteorite showed possible evidence of ancient life: small, uniformly-sized deposits of magnetite crystals found only in association with biological activity on Earth and structures that resembled fossilized nanobacteria. A 2009 followup analysis by NASA affirmed the conclusion that ancient life was the most plausible explanation for the materials and structures. The Phoenix In 2008, the Phoenix Mars Lander landed in the polar region of Mars. When it analyzed a soil sample, scientists found it to be much more alkaline than expected. According to the lead investigator for the experiment, Sam Kounaves, "We basically have found what appears to be the requirements, the nutrients, to support life" in the soil. "It is the type of soil you would probably have in your back yard, you know, alkaline. You might be able to grow asparagus in it really well." A Look at the Soil's Reactivity Now a team led by Richard Quinn of NASA's Ames Research Center and the SETI Institute in Mountain View, California, has analyzed the data to determine how oxidizing the Martian soil is. Oxidants strip the electrons from other atoms; this process can damage or destroy complex molecules like DNA. Because of the Viking results and Phoenix' own detection of the chemical perchloride, which can sometimes act as an oxidant, scientists had suspected that the soil might be highly oxidizing. But according to the results of the study, the overall reactivity of the soil is comparable to that of the soils of Earth. That doesn't mean that there is, or ever was, life on Mars. But the evidence is mounting. Add to that recent evidence from the High Resolution Imaging Science Experiment (HiRISE) camera on board NASA's Mars Reconnaissance Orbiter that there still may be liquid water flowing just under the surface of the red planet, and scientists are growing more and more hopeful. Quinn described the evidence as "very positive in terms of the potential for life to get a foothold." And on Earth, we find that once it has a foothold, life holds on tenaciously. Might we find something similar on Mars? Although we aren't sure yet, the evidence is growing.