Exobiology / Space

Poor little Pluto?

There are a lot of Pluto aficionados out there. I’m not a Pluto super-fan, but I still think of it as a planet — “My Very Easy Method Just Speeds Up Naming Planets”, but only if Pluto counts! But there’s also a sort of general feeling that Pluto is small, boring, not worth noticing.

That comes a little unstuck when you consider the fact that Pluto has been surprising researchers lately, with the news that it has recently been racked with volcanic activity, ejecting masses of water into space. Recently, when we’re talking about astronomy and geology, is relative: I don’t mean Pluto’s volcanoes erupted last Wednesday when I say it “recently” erupted (though for all I know, they did). When you’re thinking about the whole solar system, “recently” can mean a million years ago. We’re talking about the long haul!

Anyway, so what’s the evidence for these icy volcanoes, and what do they mean? The team had pictures of Pluto’s surface and atmosphere taken by the New Horizons flyby in 2015. They analysed the wavelengths of light from these photos, trying to identify what elements were present. This works because everything absorbs or reflects light in certain amounts, and with precise measurements, you can say what the light is reflecting off by seeing how much light has been reflected. In this case, what the team found were traces of ammonia.

Why does ammonia tell us that there has been recent activity on Pluto? Ammonia is quite fragile as a molecule, and usually breaks down in less than a billion years. If it’s present, something has made it recently (geologically recently). With that and the fact that the ammonia traces are clustered around in Pluto’s surface, the team put two and two together and came up with volcanism.

Virgil Fossa

Virgil Fossa, the crack in Pluto through which ammonia may have been spewed sometime in the recent past. On the right, this version of the image shows red, yellow, orange and purple pixels correspond to higher concentrations of ammonia in water ice. Image via ScienceNews.org.

But why is ammonia exciting? Most people just know it as a bad smell, and a component of cleaning products. But ice that’s full of molecules like ammonia can lead to the creation of various organic molecules that lie at the heart of life as we know it. Your DNA is made up of nucleotides, thymine and cytosine and guanine and adenine, and various experiments have found that those nucleotides can be created in exactly the situations that are theorised to exist (or have existed) on Pluto.

This is definitely still a maybe, and even if it’s true, it doesn’t mean there’s life on Pluto. It only means that (some of) the conditions for life can arise in places other than Earth, and that tells us something important in the search for life elsewhere. We’re not going to be invaded by Plutonians any time soon.

But it’s still pretty cool. Really cool. Like… the surface of Pluto, down at -233 C.

Yep, I know, I need to work on my jokes. Science has looked for my sense of humour, but the results of experiment have been rather contradictory.


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