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Asked by renick to Colm, Eoin, Joseph, Lauren, Stephen on 12 Nov 2013.
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Lauren Mc Keown answered on 12 Nov 2013:
Good question 🙂 Because we don’t know whether life exists on other planets, we have to base our ideas on what sustains life here! First of all we need an energy source – and we have that with the Sun. NASA have stated that life conditions include “extended regions of liquid water” – we all need water to survive, right? We also need the right conditions for the assembly of organic molecules – similar to Earth’s conditions. When studying optimal places for life to take place, scientists also consider places where the atmosphere contains gases which we need to live such as oxygen and gases which are good for Earth’s complex needs, which allows biodiversity to stay balanced. For example, plants can use carbon dioxide in the process of forming sugars and oxygen.
Currently what are known as the “terrestrial” or rocky planets are under investigation for habitable characteristics, but other places such as some of Saturn’s moons like Titan and Enceladus are under deep inspection for characteristics that may resemble those here on Earth such as the presence of water, a thick atmosphere and clouds in the case of Titan, and geologic activity in the case of Enceladus.
However these aren’t the only planets/moons under investigation – in the early 1990’s, planets outside our own Solar system (yes, ones other than Mercury, Venus, Earth, Mars…etc) were discovered! These are known as extrasolar or exo – planets. A mission called Kepler was sent out to investigate these and so far has found 11 BILLION of Earth – sized planets orbiting a sun – like star. They’re pretty far away so we might never know if they do have life conditions but I’ll leave it up to you to ponder the chances of one of these few billion hosting life…
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colm bracken answered on 14 Nov 2013:
Hi renick, great question. First of all we look for liquid water. This can only happen if the planet lies in what we call ‘the Goldilocks Zone’. Earth lies in this zone whereas Venus is just a bit too close to the Sun (too hot like Daddy Bear’s porridge) and Mars lies a bit too far away from the Sun (too cold like Mammy Bear’s porridge). We are at just the right distance for liquid water to be possible (Just right like Baby Bear’s porridge). The position of this zone depends on the size of the star.
Another thing that is probably essential is a large planet like Jupiter. Jupiter does the job of cleaning up all the dangerous leftovers from the beginning of the solar system. If Jupiter was not around then the Earth would still be getting bombarded with large asteroids on a regular basis. Life would simply not have enough time to evolve into complex form. -
Joseph Roche answered on 15 Nov 2013:
There is a concept called “carbon chauvinism” which is the idea that we think all life should be made from carbon because we are made from carbon. We think it would be difficult for life to originate from other elements (although silicon might work), but really we may not be considering all the possibilities. That’s the cool part – life elsewhere might be (and probably is) in a form we cannot even imagine.
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