The search for life outside of the Earth is an oft used justification for space exploration. This justification does not have the immediate benefits of economics (creating jobs), industry growth such as in telecommunications or navigation, prestige politics and national security, or practical science (such as experiments in space medicine). Even so, it is believed that one of the fundamental motivators of humanity is insatiable curiosity, and that discovering life on other worlds would be a major change in our view of the universe.
A few days ago, according to an article on DNA India, it was reported that scientists on the Chandrayaan-1 program, India’s first unmanned lunar spacecraft, found signs of organic material, including carbon compounds, on the lunar surface. They believe these signs might point to current life, or the decay of once living organisms on the moon. The article notes that amino acids, the building blocks of life on Earth, were also found in Apollo-11-returned lunar soil samples. The article notes that further research is needed to confirm these findings.
Recently, as well, was the discovery that levels of methane in the Martian atmosphere are not maintained by material from meteors. Methane gets destroyed 600 times faster on Mars than on Earth, though why this occurs is unknown. This is both good and bad for potential Martian organisms. The levels of methane on Mars must be replenished rapidly, either by release from meteor material, release from volcanism, other chemical processes, or in the metabolic waste of microorganisms. Volcanism has been ruled out due to the lack of detection of other chemicals in the atmosphere that would be released with methane, and meteors have been ruled out as not being able to account for enough of the chemical. Chemical and biological processes are left. However, with the rates at which methane is destroyed on Mars, many scientists believe that other organic chemicals, a necessity of living organisms, would be rapidly destroyed as well.
Finally, space science continues to discover new worlds where the potential for life exists. Titan, a moon of Saturn, is full of complex organic chemicals, and the Jovian moon Europa, and Saturnian moon Enceladus might harbor under-ice oceans which may contain living organisms. According to an article on Space.com, two more super-Earths (planets with more mass than Earth but less than gas giants) have been discovered in other star systems. Astronomers are moving steadily toward the discovery of terrestrial-mass sized planets. This does not mean these extra-solar planets contain life, however, or that life cannot be discovered on worlds vastly different from Earth.
It should be noted that there is a lot of hype around reporting on the search for life (and this article is probably guilty of this as well). What, however, is the benefit of conducting this search? Is it worth the time and funding that is needed to make these discoveries? Will the discovery of life on another world make a difference to human society here on Earth? If life is not common in the universe, or is only found on Earth, how will the ongoing lack of evidence of life on other worlds affect humanity? Finally, the search for life on other worlds is part and parcel of the scientific understanding of various planetary environments. Is the scientific study of these other environments and their comparison with Earth’s environment worth the effort?