The Search for Alien Life
Most people have looked up at a starry sky and wondered whether there is life beyond our own blue planet. Is our world a unique oasis of life or are there other planets that harbour life?
In recent years advances in two areas of science have caused quite a stir with those interested in finding alien life.
SEARCH FOR EXTRASOLAR PLANETS
One of the basic questions when looking for extra terrestrial life is:
How many planets are there outside of our own solar system?
Is our sun unique with its oddball family of worlds orbiting around it or do other stars also have orbiting planets?
In the 1990s astronomers found evidence of the first exoplanet (a planet orbiting another star). Since then over 5000 exoplanets have been found in over 4000 solar systems. Many of these planets are roughly earth size and many appear to be orbiting in the 'Goldilocks Zone' - not to close to their star where water would evaporate and not to far away so that any water would be frozen.
If we have found so many of these planets on our doorstep then there are likely to be many trillions of these worlds spread out around different galaxies. This seems to greatly increase the chance of alien life existing somewhere.
ASTROBIOLOGY
This is another branch of science that has advanced rapidly. Astrobiology seeks to understand the origins and evolution of life on earth and whether life exists elsewhere.
One area of research covers the search for life in earth's most hostile environments. We know that life flourishes in the rainforests and temperate zones of earth but these types of environments aren't found on any other planets in our solar system. What would be exciting is the discovery of life at the bottom of frozen lakes in Antarctica or organisms living deep in the earth's rocky crust because these environments can be found on other planets.
Recently some new residents were discovered in Idaho. They consume hydrogen, breathe carbon dioxide and belch methane (so there goes the neighbourhood).
They are tiny organisms called Methanogens and they live in the earth's crust 660ft below the (Idaho) surface.
Their discovery is extremely significant because they survive without the need for sunlight or oxygen. They may be exactly the type of life we should look for when we search for extraterrestrial life.
EUROPA - A MOON OF JUPITER
When looking for life in our solar system, scientists have focused a lot of attention on Mars as being a potential cradle of alien species. However, another world that has caught the eye is Europa, one of Jupiter's moons. When the Galileo probe visited Jupiter and its attendant Galilean moons, Europa was thought to be a frozen ball of rock and ice. However pictures taken by the probe clearly revealed a series of cracks and fissures across the moon's surface. There is only one other place in the solar system that has this appearance, the frozen arctic seas on earth. It appears that deep below the icy surface Europa has a system of giant oceans. The composition of these oceans is unknown but there is a chance they support life.
How do we know that life could survive below massive permanent layers of ice in oceans with no light reaching them? Because in similar conditions here on earth astrobiologists have also found life.
Lake Vostok is a huge lake that lies under ice that is 10 times as deep as the Empire State Building is tall. By drilling over 11,000 metres down samples were taken of freshwater ice and microbes were found living in these samples. So the saying "Where there's water there's life" has been taken as far as we can push it on earth. The belief that liquid water may exist on Europa and was once prevalent on the Martian surface gives astrobiologists hope that the discovery of alien life may not be too far away.
