Hey everyone! Time for an article about THE WARMING EFFECTS OF CARBON DIOXIDE IN THE ATMOSPHERE! Because no-one’s done that for a while.
The interesting twist here, of course, is that the atmosphere in question is the one that currently swaddles Mars like a threadbare blanket. The Martian atmosphere is thin, so thin that it doesn’t carry out any sort of meaningful greenhouse effect, which is one of the reasons the Red Planet is so much colder than Earth. But recent findings suggest that under the surface of the planet much of the rock is carbon-heavy, which may mean that the atmosphere once was, too.
This has led people - including us – to say that it means it is more likely that life once existed on the planet, and even that it may still hide in its hidden depths. That’s true, but it’s not direct evidence in any sense that life happened: merely that the conditions were more suited to life, in one of the forms that we might expect to find it. The problem with Mars, from the point of view of developing life, is that it is cold, and dry. But, according to Dr Lewis Dartnell, an astrobiologist at UCL, it has not always been thus.
“The extensive landscape evidence for flowing water (ie. the great channels, flood plains and crater lakes) suggest that the atmosphere was much thicker in the past, allowing water in the liquid state,” he says. But this would have been billion of years ago, and billions of years ago the Sun was much dimmer. “It would have been even harder for Mars to insulate itself enough to be warm and wet”, he says. The apparent conflict between those two facts is known as the “faint young Sun paradox”; a similar problem faced scientists researching the early life of the Earth.
On Earth, it is hypothesised, the warm, wet conditions needed for life to start were provided by a thick overcoat of carbon dioxide, carbonyl sulphide and other greenhouse gases. Later, these gases were used by early plant-like life, and the air was filled with oxygen.
On Mars, it seems, something similar – up to a point – may have happened. Satellite examinations of a meteorite crater on the surface of Mars suggest that the minerals buried deep below the crust – four miles below, in fact – are rich in carbonates. This suggests that there may once have been a carbon-rich atmosphere.
Life, as we know it, needs warmth, and carbon, and water. It seems more likely, now, that Mars had all of those things, so it is more likely that Mars could have supported life. But, as Dr Dartnell puts it: “This geological evidence for ancient abundant carbon dioxide certainly supports the predictions of a thicker greenhouse atmosphere.
“But it only tells us that the conditions on Mars would have been more conducive for life – it does not provide any supporting evidence that life ever arose.”
If convincing evidence for Martian life is found, it will be, I think quite literally, the biggest news in human history. It will mean it is very likely that the stars are teeming with life – if it can arise twice, independently*, in one little solar system – and will significantly raise the chances that intelligent life is common too. Each of these little suggestive hints that it has happened are fascinating. But we’re not there yet.
*Independently, of course, is the key. If it transpires that either Mars seeded us or we seeded Mars, via some huge meteor collision blasting microbe-covered rocks into space and having them land on the other planet, that will be fascinating, but it will say nothing about how likely life is elsewhere in the universe.http://blogs.telegraph.co.uk/culture/tomchivers/100047939/mars-carbon-dioxide-and-ancient-global-warming-and-you-know-martians/