Space - Tullamore Astronomical Society

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