Space - Tullamore Astronomical Society
Space - Tullamore Astronomical Society
Space - Tullamore Astronomical Society
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Goldilocks and the (many) more than three<br />
planets: some notes on Astrobiology<br />
By Girvan McKay, <strong>Tullamore</strong> AS<br />
What is Astrobiology? I hope I hear you ask.<br />
According to my encyclopaedia: Astrobiology is defined<br />
as: “The multi-disciplinary study of the origin,<br />
distribution and destiny of life in the universe. It<br />
addresses the questions of how does life begin and<br />
develop, does life exist elsewhere in the universe, and<br />
what is life’s future on Earth and beyond. It is a major<br />
goal of NASA’s science programmes.”<br />
The study of Astrobiology (also known as<br />
Exobiology) is above all associated with the name of the<br />
late Carl Sagan, who is also regarded as the first<br />
astrobiologist. In a way it’s a little strange to refer to it<br />
as a study, since to study anything you have to have<br />
some data to study. In this sense Astrobiology is like<br />
Theology, which purports to be the study of God. But if<br />
God, by definition, is invisible and unknowable, what is<br />
there to study? It isn’t even possible to prove the<br />
existence of God by either argument or research.<br />
The same applies to Astrobiology. We don’t<br />
know whether there is any kind of life outside of our<br />
own planet Earth. But in both cases, the search still goes<br />
on. Also, in both cases, it’s a matter of faith rather than<br />
proof. We haven’t as yet found any evidence of<br />
extraterrestrial life. Within our own solar system<br />
investigations are still being carried on to see if there is<br />
any evidence of existing or extinct life on Mars. So far<br />
nothing has been found although US scientists claim to<br />
see signs that there was once water there, and liquid<br />
water often indicates the presence of life. There are also<br />
hopes that there might be liquid water under the surface<br />
crust of Europa, Jupiter’s second satellite.<br />
You’ll realise, of course, that the search for life<br />
doesn’t necessary mean the search for intelligent life.<br />
Probably most astrobiologists would be happy if they<br />
discover any kind of life elsewhere in the solar system or<br />
outside it. They would be jumping up and down with<br />
joy if even all they found were something like a<br />
bacterium, an amoeba, a fungus, a lichen, a slime mould<br />
or anything else that was alive, even if it couldn’t read,<br />
write or think and looked like something in your dist bin<br />
or on mouldy cheese.<br />
Also associated with Carl Sagan and<br />
Astrobiology is the SETI programme, although this is<br />
the search for extraterrestrial intelligence - in other<br />
words for intelligent life, not just any kind of life. Back<br />
in November 2001 I gave a talk on ‘Life in the Universe’<br />
in which I mentioned the SETI programme. For those of<br />
you who weren’t at that TAS lecture or who fell asleep<br />
during it, I’ll digress for a moment to say something<br />
about SETI.<br />
SETI was a research programme originally<br />
managed by NASA’s Ames Research Centre. It was<br />
aimed at using large radio telescopes to try and detect<br />
artificially generated radio signals from interstellar<br />
space. (I’m quoting here from another article in my<br />
encyclopaedia.) The hypothesis behind the belief that<br />
life might exist elsewhere in our galaxy is based on<br />
telescopic and spacecraft evidence that organic<br />
molecules are common in space and also on the<br />
hypothesis that planetary formation is a common byproduct<br />
of star formation. The SETI programme was<br />
first proposed in 1959 and thirty very limited searches<br />
were carried out. It was an American astronomer called<br />
Frank Drake who in 1960 was the first person to conduct<br />
a radio search for signals from extraterrestrial<br />
civilisations.<br />
Drake is mainly associated with an equation he<br />
proposed to organise this search. (By the way, Drake<br />
says himself that he only meant his equation as a<br />
gimmick and he was surprised when it was taken<br />
seriously and is now included in astronomy textbooks.)<br />
Here is the equation:<br />
N = R* fp n e fl fi f c L<br />
The factors indicate the following: R* , the number of<br />
stars; fp , the number of stars with planets; n e , the<br />
number of planets with habitable environments; fl , the<br />
fraction of these on which life has originated; fi , the<br />
number with intelligent life;<br />
Réalta – Volume 7, Issue 2 – November/December 2005 – <strong>Tullamore</strong> <strong>Astronomical</strong> <strong>Society</strong> 17