To wrap up the series, we’ll look at what origin of life theories mean for the search for extraterrestrial life and what kind of clues could indicate that life may have been or may be present on other planets.
Introduction
So besides coming up with potential models in the lab or on a computer for how life arose on Earth, what else are scientists doing to delve deeper into the field of astrobiology and to get a clearer view of how life could have originated in the universe?
Well, for one thing, they are most certainly not giving up on refining the models we’ve touched on in this series, nor are they giving up on looking for evidence that could support one or more of these models. Indeed, recently it was announced that the amino acid glycine was found among material collected from a comet in space. Being an amino acid, glycine is an important molecule related to life, as amino acids are the building blocks of proteins and proteins are the workhorses of cellular processes. Particles from the comet Wild-2 were collected in 2004, sent to Earth in 2006 and analyzed with great care before data was confirmed. This find adds evidence to the idea that life may have had an extraterrestrial origin and “found” its way to Earth on objects like comets.
Extreme Environments
But so many places in the universe, and even on primitive Earth, are and were so very hostile: freezing temperatures, highly acidic conditions, etc. Venus has clouds of sulfur, and Titan, one of Saturn’s moons, has lakes made of methane (among other things). How could life have originated and survived either in the universe or on early earth? Well, in the 1970s, scientists started making startling discoveries of organisms living in extreme conditions on the present day Earth. These organisms were dubbed the “extremophiles.” Each of life’s three domains, the archaea, bacteria, and eukaryotes, has examples of extremophiles.
For example, organisms have been found at a depth of nearly 1200 feet in Antarctica’s frozen Lake Vostok, in the highly salty Dead Sea in Israel, in hot springs in Yellowstone National Park as well as around the volcano, Mount Vesuvius, in Italy, The bacteria living around the volcano not only have to deal with high temperatures, but with incredibly acidic conditions as well. Microbes have also been found living four miles below the surface in Washington State, USA; they feed off hydrogen gas to survive. Many more examples of extremophiles have been discovered since the 1970s. 
Biosignatures
Well, fine. So we have the building blocks of life being present in the universe, and we have organisms that could potentially survive the harsh conditions found throughout the universe. But what if life was only present for a short period of time on a planet? How would we know we should study a planet because it once harbored life in the distant past?
Scientists are very creative people and they have come up with ways of studying the chemistry and geology of a location to find what are called “biosignatures”, biochemical signs that are the result of life processes. The most famous of these attempts to study biosignatures in space took place in the 1970s, when the Viking Landers were sent to Mars. The Landers were equipped with a host of tools to study Martian soil in order to determine if its geochemistry offered any evidence that it had been influenced by life. The results were inconclusive, but the idea paved the way for more experimentation of this nature. Today, an instrument called Urey: Mars Organic and Oxidant Detector is being prepped by the European Space Agency to be sent to Mars in 2013 for similar experiments.
Astrobiology: Origins of Life on Earth and in the Cosmos
This multiple part series will explore the theories on the origin of life on earth, what these theories could mean for the presence of extraterrestrial life and how astrobiologists are searching for life on other planets.