No.
The surface of Comet 67P as seen by the Rosetta probe. [Credit: ESA/Rosetta/MPS for OSIRIS Team... [+]
Oh, I suppose you want more than that (though I'm tempted to say "hell no" and leave it at that). It's a fairly easy claim to dismiss: comets aren't very hospitable to life as we know it, so ordinarily we wouldn't even be having this conversation. However, a pair of astronomers claimed in a talk at the National Astronomy Meeting in Wales that certain aspects of Comet 67P/Churyumov-Gerasimenko are best explained by the presence of microorganisms.
Suffice to say it's a radical claim, and one which would require a lot of evidence to convince researchers. After all, we only know of one world where life exists —Earth — and no obvious signs of life anywhere else in the universe (yet). While life thrives in a huge variety of environments on Earth, from deep underground to undersea volcanic vents to clouds high in the atmosphere, our space probes haven't found any microbes or little tentacled monsters on
The basis for the new claim is twofold: the recent discoveries by the Philae lander of organic molecules on Comet 67P, and the potholes that are actively forming on the comet's surface. The two researchers, Max Wallis of the University of Cardiff and Chandra Wickramasinghe of the Buckingham Centre for Astrobiology, claim that the comet's changing surface is most likely produced by microbes, similar to those found under the ice on Earth.
While colloquially "organic" refers to agricultural practices, to scientists it simply refers to molecules including the element carbon. Comets are covered in organic molecules, making them look quite dark up close. Though organic compounds are essential to life as we know it, life isn't required to make organics. And that's the first problem with Wallis' and Wickramasinghe's claim: organic molecules are very common in the Solar System and beyond, without any need for living things to make them.
The second problem is that we know comets are active bodies. The most famous feature of a comet is its twin tails of gas and dust, which are created when the Sun bombards it with light and the particles known as the solar wind. This bombardment heats the comet's surface and knocks material loose. The potholes and jets the Rosetta probe sees forming on the surface of Comet 67P are almost certainly due to that process, not the presence of life under the ice.
The third problem is that one of the researchers, Wickramasinghe, sees life everywhere he looks. His was the false claim several years ago that a Martian meteorite contained diatoms — single-celled plant life. He has also claimed that SARS came from space. To put it mildly, we should take any of his claims about life in the Solar System with enough salt to fill the ocean on Uranus.
But you don't have to take my word for it: planetary scientists and astrobiologists, including Rosetta's science lead Matt Taylor, have expressed polite skepticism over the claims of cometary life. While Comet 67P is a very interesting world, with some mysterious aspects, there's absolutely no reason to think that life is responsible for any of the features we see.
So what would be a clear sign of life? The answer is tricky, but the short version is that we should be looking for very unusual chemicals or chemicals in abundances that couldn't be made by non-living processes. For example, Earth's oxygen atmosphere couldn't have existed without microbes that altered the chemical balance of the air, because molecular oxygen (O2) wasn't present in the earliest days of our planet. Organic molecules are common without life: we need to see stuff that is the result of living things breathing or pooping or dying and decaying. Comet 67P doesn't have those signs.
Philae is the surface-operations part of the European Space Agency's Rosetta mission. It landed on Comet 67P last year, and recently woke up from its inadvertent hibernation.
