Ever since we started seriously entertaining the idea that life might exist elsewhere in the universe, we have posited that one of the requirements is liquid water. After all, it is a requirement on Earth, at least for life as we know it.
Without complicating things too much, let鈥檚 assume that is true. We used to think liquid water was a rarity, just as we thought planets orbiting other stars was unusual.
Why we would have ever thought that once we started to understand the universe is governed by certain laws is, I believe, a hangover of the faith-based concept that humans are somehow unique.
Last week, scientists confirmed yet another moon in our very own solar system harbours liquid water under a thick crust of ice. Ganymede, Jupiter鈥檚 largest moon and the biggest in the solar system appears to have a subsurface ocean 100 kilometres deep according to evidence obtained from the Hubble Space Telescope.
That brings the number of moons in the solar system with liquid water to three.
We also now know that Mars used to have liquid water.
It is starting to appear that rather than water being an exception, it is probably a rule.
The same thing could be said about planets. The more we look the more we find until one must extrapolate that they are pretty much everywhere.
This really should come as no surprise. After all, stars and galaxies and novae and nebulae and black holes etc. etc. exist everywhere. Why wouldn鈥檛 planets and water?
As one NASA researcher put it: 鈥淭he solar system is now looking like a pretty soggy place.鈥�
So, if planets and water are becoming a rule, by extension so should life. If the conditions for life exist, the chances that it will develop are probably pretty darn good.
Even our experience here on Earth kind of suggests the same. Every few months we discover life in places we never thought it could, in lightless caves, on vents in deep ocean trenches, under Antarctic ice.
It puts me in mind of one of the great lines in cinematic history, albeit from perhaps not one of the great movies.
In the 1997 Jodie Foster film Contact, the young version of Foster鈥檚 character Ellie asks, 鈥淒ad, do you think there鈥檚 people on other planets?鈥�
Her dad responds: 鈥淚 don鈥檛 know, Sparks. But I guess I鈥檇 say if it is just us... seems like an awful waste of space.鈥�
An awful waste of space indeed.
