Top 10 Places To Find Alien Life

There are billions of stars in our own galaxy and even more in galaxies beyond. Is there is a good chance of finding life beyond Earth?

Over 22,000 meteorites have been documented on Earth, and many of them have been found to contain organic compounds, some even containing what astrobiologists believe are fossil remains of bacteria in meteorites. If the fossilised remains of bacteria are confirmed, this gives excellent evidence to support the theory of panspermia, which is the idea that life came from outer space and that planets exchanged life. Bacteria on Earth survive in extreme environments, from sulphuric volcanoes to the icy depths of the Arctic.

Mars has long been a target for extraterrestrial life hunters, but its arid and barren landscape has turned our attention away from finding little green Martian men to finding simpler life forms. One of the key ingredients to life is water, and with the recent discovery of water on Mars, the likelihood of finding life, albeit micro-bacterial, has significantly increased. Because Mars's surface is uninhabitable with a thin atmosphere, cold temperatures, an oxidising environment and harmful UV radiation, it's a tough place to live. Below the surface, however, conditions may be more favourable, and that is where we are likely to find life today. Perhaps there was life on the surface in the past, but today, it will be living below ground.

Europa has recently emerged as one of the top locations in the Solar System for potential conditions for supporting life. It is believed that an ocean could be hiding beneath Europa's icy surface, one that may contain high levels of hydrogen peroxide, which can break down to form an oxygen-rich environment.

It is thought that bacteria could live under the surface clustered around hydrothermal vents driven by geothermal energy, much like we see on Earth, or from gravitational forces caused by Jupiter's gravity.

NASA scientists had declared Callisto a "dead and boring moon" until the discovery of a possible salty ocean beneath its surface.

NASA's Galileo spacecraft flew by Jupiter's second-largest moon in 1996 and 1997 and found that Callisto's magnetic field varied, indicating currents. In 2001, Galileo detected that an asteroid had struck the moon, forming the Valhalla impact basin. Usually, such an impact would cause intense shock waves to ripple through the planetary body, but Galileo couldn't find any evidence of this, leading scientists to theorise that a watery ocean could have softened the blow.

Could this frigid moon provide a welcoming environment for life? Scientists are looking closer at this Saturn moon and finding more and more potential building blocks for basic life there, despite Titan's surface temperature of -185° C.

NASA's Huygens probe detected what looked like liquid methane on the mini planet's surface in 2005. In May 2010, two teams of scientists announced that NASA's Cassini orbiter showed Titan was harbouring an unusual chemical combination of hydrogen and acetylene.

When Cassini did a fly-by through one of Enceladus's geysers spewing ice and gas in 2009, the probe detected carbon, hydrogen, nitrogen, oxygen and even salt - all key elements for supporting living organisms. Theumes' temperature and density could indicate a warmer, watery source beneath the surface.

Some estimates show that the Milky Way alone harbours around 400 billion stars and countless exoplanets, and that's just within our galaxy. So, there could be billions of habitable cosmic bodies out there.

Kepler has discovered many, many exoplanets, some of which are located within the habitable zone of their star, including KOI-1686.01 (Kepler Object of Interest), which is a similar size to Earth and sits in roughly the same orbit as its parent star where liquid water can exist. Other potential exoplanets include Kepler-62e and Gliese 667 Cc.

The Orion Nebula is a stellar nursery in the Milky Way which has recently been investigated as a potential gold mine for finding life.

In May 2010, the European Space Agency's Herschel Space Observatory announced that the Orion Nebula showed signs of having life-enabling organic chemicals. Looking through the data collected by the telescope, astronomers were able to detect a pattern of spikes for various life-supporting molecules: water, carbon monoxide, formaldehyde, methanol, dimethyl ether, hydrogen cyanide, sulphur oxide and sulphur dioxide.

While life may not exist in the nebula itself, these organic compounds can potentially seed nearby exoplanets with life-giving compounds.

In 2005, an international team of astronomers discovered that dying red giant stars could act like a defibrillator and bring icy planets back from the dead. This rebirth could also lead to new breeding grounds for life, albeit challenging.

Red Giants pose problems for life, including the possibility of tidal lock and severe solar radiation flares, but in terms of detectability, they show particular interest for planet hunters as a transiting terrestrial-class world in the habitable zone of a red dwarf is going to block a larger part of the star's light than a similarly sized world orbiting a larger star.

The universe is an unimaginably vast space filled with planets, stars, nebulae, gas, dust, comets - and it's impossible for us ever to explore it all.

Are we even looking for the right "stuff"? Astrophysicist Stephen Hawking theorises that life could exist that is not carbon-based. If that's the case, is it possible that we have already found "life" and missed it as we were looking for "ourselves"?

The quest to find life beyond this planet continues. If aliens are found, let's hope they're friendly.