It's very probable that alien life exists out there. But when we finally encounter such life forms, how do we know that the figure we're staring at is indeed an alien?

The US National Academy of Sciences is convinced that trying to search for any life forms similar to those on Earth would cause us to easily miss the actual aliens that take on a more bizarre appearance.

NASA commissioned a report from the National Research Council regarding the search of alien life forms. The resulting report's gist can be summed up as thus: "Nothing is quite as it seems."

Space experts said that those looking for aliens should be searching with an open mind. "The purpose of this whole report was to be able to look for life on other planets and moons with an open mind ... and not maybe miss some other life form because we are looking for some obvious life form", said John Baross, a professor of oceanography for the University of Washington.

Recent discoveries of organisms lurking in places where life shouldn't be possible under normal circumstances (called extremophiles) are changing the scientists' perception on where and how life exists in outer space. Prof. Baross also added that the existence or non-existence of water is not necessary critical in the search of alien life.

With so many concepts cropping up with each new discovery in outer space, it's entirely possible that strange chemicals such as methane and ammonia are being used by other organisms in the same way as humans and most Earth-dwelling creatures use oxygen. "There are so many theories about what life is and what could be a living system," Prof. Baross said.

For the meantime, NASA as well as other groups are still on the search for alien life forms. Robots dropped off in Mars are hard at work looking for water, or traces of water. Telescopes scan the outer space for planets with bodies of water.

NASA has been advised to look within our own solar system again for clues of life, such as Venus or even Saturn's moons, Titan and Enceladus. Baross said that it would be best to try and think out of the box for a bit, and find other ways or possibilities on how life exists on other planets besides water.