Search for aliens

Photo: nation.com.pk

One of the best chances for finding life in the solar system is on Jupiter's moon Europa.

On page 190 of the Observer's Book of Astronomy, published in 1962, author Patrick Moore wrote about Mars:

• "The planet cannot be regarded as overwhelmingly hostile, and the existence of vegetation can hardly be denied, although as yet there is no positive proof.”

This statement, by a leading figure in astronomical writings, reflects accurately the thinking of the time.

Knowing what we know today about Mars, we wonder what this conclusion was based on. It also shows how much our ideas have changed regarding places to look for extraterrestrial life.

In 1877, astronomer Giovani Schiaparelli observed linear features on Mars that he described as "canali,” the Italian word for "channels.”This word can describe naturally occurring features.

However, somewhere this word was mistranslated into English as canals, which are different things entirely.

Thus was born the idea of the Martians fighting the drying up of their world by setting up a global water management system based on a complex network of canals.

In 1894, Percival Lowell built an observatory near Flagstaff, Ariz., just to map the canals and study Mars.

This created a widespread belief that the Red Planet had living things on it, and in a plethora of science fiction stories, some of those living things compared our warm, wet world with their cold, dry world and decided a move was in order.

Lowell and many others since saw that in the Martian spring, a wave of darkening moved equatorward from the polar caps. This was explained as vegetation greening up as meltwater was released by the warming poles.

This opinion was supported by our eyes making grey look green when seen against a red background.

Our delusions were shattered when spacecraft sent us back closeup pictures of Mars, firstly from nearby space and then from the planet's surface.

Mars was indeed wet and warm once, and there could have been life, but today as yet we have found no sign of it other than the odd trace of methane that is sometimes detected.

The story is a good illustration of how our search for extraterrestrial life has evolved. We used to think that we were most likely to find life in the solar system on the planet most like ours.

Today, many scientists think the most likely locations are Europa, a moon of Jupiter, and Enceladus, one of Saturn's moons.

Both are so far from the sun they should be frozen solid. However, they are getting a lot of heating from the continuous gravitational kneading due to the tidal forces generated as they orbit their giant, host planets.

Our interest in these objects has been triggered by what we have seen in our own oceans.

Around the Mid-Atlantic Ridge and assorted other places on the bottom of our deep oceans, outflows of hot, mineral-rich waters are supporting communities of bizarre creatures who owe nothing to the sun's light or heat.

The heat released by tidal forces inside Europa and Enceladus must be doing the same thing.

Fly-bys by our space probes suggest that under the icy envelopes of these bodies there are deep, dark oceans.

Moreover, there is no reason to suppose that those outflows of hot, mineral-rich water are not happening on Europa and Enceladus.

Therefore, could there also be communities of bizarre creatures living around them?

Enceladus gives us another line of evidence. The tidal heating is enough to drive eruptions of water through the icy surface and into space.

Spacecraft have analyzed this water and found it to contain the organic, chemical building blocks of life, just as we would find in the water of our own oceans.

Although our search for Martian life goes on, we now realise that when we do find life elsewhere in the solar system, there is a good chance it won't be on Mars.

Maybe the Martians will be us.

• Jupiter and Saturn lie low in the southern sky after dark.
• The moon will be New on the 30th.

This article is written by or on behalf of an outsourced columnist and does not necessarily reflect the views of Castanet.