When it comes to life outside Earth, all eyes are on Mars and Europa, but new organisms may be lurking even at the edge of the Solar System.
Analysis so far seems to indicate a liquid ocean beneath the frigid surface of Pluto, which could mean life exists there, although not as we know it. Professor William McKinnon from Washington University in St. Louis is the co-author of two of four new Pluto studies published this week in Nature. He argues that in the dwarf planet's viscous ocean, there might be microorganisms.
“What I think is down there in the ocean is rather noxious, very cold, salty and very ammonia-rich – almost a syrup,” Mckinnon said in a statement. “In fact, New Horizons has detected ammonia as a compound on Pluto’s big moon, Charon, and on one of Pluto’s small moons. So it’s almost certainly inside Pluto.”
In previous studies, he showed that nitrogen ice on the surface of the dwarf planet experienced constant forces that change the region known as Sputnik Planitia, the famous heart of Pluto. According to McKinnon’s latest paper, based on the orientation and gravity of Pluto, the ocean is 950 kilometers (600 miles) across and 80 kilometers (50 miles) thick.
The ocean was formed via an ancient impact that provided a space for the ocean to fill. However, the ocean would have quickly frozen if it was made of ice, so a different composition is required.
“All of these ideas about an ocean inside Pluto are credible, but they are inferences, not direct detections,” McKinnon added. “If we want to confirm that such an ocean exists, we will need gravity measurements or subsurface radar sounding, all of which could be accomplished by a future orbiter mission to Pluto. It’s up to the next generation to pick up where New Horizons left off!”
Given the dramatic differences between Earth and Pluto, the little critters that might inhabit the ocean are likely not what you would expect.
“Life can tolerate a lot of stuff: It can tolerate a lot of salt, extreme cold, extreme heat, etc. But I don’t think it can tolerate the amount of ammonia Pluto needs to prevent its ocean from freezing – ammonia is a superb antifreeze,” he continued.
“It’s no place for germs, much less fish or squid, or any life as we know it. But as with the methane seas on Titan – Saturn’s main moon – it raises the question of whether some truly novel life forms could exist in these exotic, cold liquids.”
There are many icy bodies at the edge of the Solar System, and if oceans can survive on Pluto, there might be many more interesting geologies left for us to discover.