Astrobiology

According to NASA, "Astrobiology is the study of the origins, evolution, distribution, and future of life in the universe." It is a huge subject and hence involves a multi-disciplinary approach with scientists from many fields having to work together to find out just if and where life does exist beyond the Earth. To introduce us to the subject Dr Mike Leggett from Milton Keynes Astronomy Society gave us an overview of the science and some of the latest developments. To narrow down the possible list of places to look - the Universe is a pretty big place, after all - it is logical to look for other planets with suitable conditions for life as we know it. So, the body needs to have adequate amounts of liquid water, environmental conditions that are conducive for the formation of complex organic molecules and some sort of energy source that the life forms can tap into to sustain themselves.

Of course this does not preclude the search for life in our own Solar System. In fact the science could develop to a stage whereby we could identify those chemical environments that are on the verge of playing host to life. At present the shortest odds on places to find life are beneath the surface of Mars or on the moons Titan or Europa. Closer to home on our own planet scientists are discovering life in the most unlikely of places: Antarctic deserts, deep within cave systems, in hot bubbling acidic pools and in the dark deep depths of the ocean where no light can reach. A lot of the organisms that can cope with these extreme environments have been named "extremeophiles". These organisms look similar to bacteria under the microscope but they are a distinct type of life known as Archaea. These are among the earliest forms of life that appeared on Earth nearly 4 billion years ago.

At present there is some controversy related to an ice-core drilling operation in the Antarctic. British and Russian scientists identified Lake Vostok back in 1996. The lake is 250km long, 500m at its deepest and is capped by a 4km thick ice sheet. It is thought that conditions in the lake may resemble those in the predicted ocean below Europa's icy surface. Drilling had stopped a short distance above the lake's surface but now the Russian team want to continue and break through. Other scientists are horrified at this suggestion as the drill is bound to be highly contaminated with surface bacteria and engineering fluids used to keep the drill hole from freezing up.The drillers want to go ahead as they say that the lake is sterile as it has too much oxygen to allow for life. They did find some microbes in the ice cores directly above the lake but they are saying that these have been introduced from the surface somehow. If the lake is found to be sterile it will be the first lifeless body of water found on Earth.

One less contentious sample-return mission is that of the Stardust spacecraft. It has successfully flown through the tail of Comet Wild- 2 capturing a sample of the debris. In early 2006 it will return to Earth and drop a capsule containing the sample into the atmosphere. Hopefully if all goes to plan it will parachute to the ground somewhere in the desert west of Salt Lake City, USA. Primarily the mission is aimed at the analysis of cometary material relating to the formation of the Solar System but it may give hints regarding the possibilities of life "out there".