Monday, 23 January 2012

Kepler 22-b: how Earth-like?

Kepler-22b is the first exoplanet to be discovered which has 3 basic characteristics fairly similar to those of Earth:

Size: not too different - 2.4 times the diameter and 7.1 times the volume, assuming it is spherical. Its mass is not given on my Exoplanet iPhone app presumably because of the way it was detected.

Parent star: yellow dwarf,  similar to our sun (but G5 as opposed to G2V)

Orbit:  in the ‘habitable’ zone. If it had our atmosphere its surface temperature would be a comfortable, life-supporting 22 deg C

From  the Exoplanet i-phone app, the orbit seems to be circular since its eccentricity is listed as zero; but I’m wondering if this is a mistake because I’ve not come across any media reports which highlight this. A fairly circular, rather than highly elliptical, orbit is quite significant because it is a necessary (though far from sufficient) condition for advanced carbon-based life to develop. Too oval-shaped a path round the sun results in extremes of temperature which would probably limit the range of life forms which could be established, or even rule out any at all.

If the temperature could be directly measured and turned out to be anything like 22 deg C it would be headline news because it would probably mean it had an Earth-like atmosphere, and our atmosphere is a product of the mix of animals and plants on its surface over billions of years as well as plate tectonics and protection from comic rays. In fact to be habitable in the sense of having life as we know it the planet would have to have life on it in the first place to produce the right temperature range. One might call this habitable zone tautology. The conditions for life are produced by life. A planet needs life on it to produce the right temperature, along with the right astronomical conditions, but it needs the right temperature to sustain life.  But as stated elsewhere on this blog (see Our precious planet  and Earth-like planets: is the universe teaming with life?  ) a wide range of conditions have to be met for life to have a chance of  evolving. Since writing those posts  I’ve come across additional conditions and will try to put together a more exhaustive list for a future posting.

As these exoplanet discoveries roll in there are three questions to keep in mind regarding the frequency of extraterrestrial life:

  • How many planets apart from Earth, if any, have the necessary surface conditions for life of even the most elementary kind to get started (anaerobic bacteria etc., which don’t breathe oxygen)?

  • How many planets, if any,  have the necessary conditions for these to evolve into higher, oxygen-breathing forms, perhaps culminating in self-conscious intelligent beings?

  • How many, if any, already have advanced extraterrestrial life on them?

So the first step is to look at our own solar system, preferably by manned exploration. If bacteria or other life forms are found, say, on Mars or below the ice on the Jovian satellite Europa, it will indicate that bacteria may be common in the universe but that very special conditions are needed for it to evolve into something more exciting. It could even be that dormant bacteria are generated in some extraordinary way by stellar or interstellar processes then pushed by light pressure through the universe until they reach a truly Earth-like planet , a process known as panspermia– although it is still possible that the Earth alone is the magic crucible of creation. It will certainly be worth continuing with SETI, although hopefully in a more imaginative way than looking for modulated radio waves.

If no bacteria or, even viruses, are found anywhere else in our solar system it will point to life here being truly unique unless some other form of non-biological life beyond our imagination and powers of detection has evolved.

I’m sure some of the readers of this post know more about astrobiology than me so please use the comments box  so we can all benefit from your input. Alternatively just send an email to the address below.

Author, 2077 AD