It’s four months since New Horizons flew past Pluto, capturing the 2015 photo of the year (probably) as it went. But what have we learned? Well, Pluto might have ice volcanoes, certainly has spinning top moons, and the Edgeworth-Kuiper Belt may be filled with bigger rocks than first imagined.
“The New Horizons mission has taken what we thought we knew about Pluto and turned it upside down,” said Jim Green, director of planetary science at NASA Headquarters in Washington.
Green was speaking at a major meeting of astronomers following months of New Horizons research.
Why the outlandish claims of revolutionary thinking?
Pluto, as seen from the Long Range Reconnaissance Imager aboard NASA’s New Horizons spacecraft
Cryovolcanoes, as cool as they sound
Well, first up, let’s look at two features that Green’s team think might be cryovolcanoes, emitting slurries of water, ice, ammonia, nitrogen or methane from their tops.
From satellite imagery, they are basically two massive mountains with holes at their top, looking pretty much like what volcanoes look like on Earth.
“If they are volcanic, then the summit depression would likely have formed via collapse as material is erupted from underneath,” said Oliver White of the New Horizons team.
“The strange hummocky texture of the mountain flanks may represent volcanic flows of some sort that have travelled down from the summit region and onto the plains beyond, but why they are hummocky, and what they are made of, we don’t yet know.”
Gif of Pluto images from New Horizons approach
Volcanoes add clues to Pluto’s surface, and beyond
If Pluto proves to have volcanoes, it will provide an important new clue to its geologic and atmospheric evolution – nothing like this has ever been seen in the deep outer solar system.
Of course, that’s because we’ve never gotten close enough to look, properly, with New Horizons’ work revealing that Pluto’s surface enjoys a varying age range, from ancient to intermediate to relatively young.
Now in historical terms that would mean Ancient Egypt, Middle Ages and Industrial Revolution. But we’re not talking history, we’re taking geology.
Locations of more than 1,000 craters mapped on Pluto by NASA’s New Horizons mission, via NASA/JHUAPL/SwRI
And the only way to establish age is counting the crater impacts, with the fairly understandable assumption that the more the impacts, the older the region.
Some of the surface, so, is estimated at 4bn years old, right when Pluto was formed, with other areas as young as 10m years old.
This area is on the left hand side of Pluto’s heart, with other areas falling in between those two ages. By the way the heart on Pluto drew some pretty genius gifs from around the web.
Edgeworth-Kuiper Belt, we hardly knew you
However, what’s somewhat more surprising is how, by counting the crater impacts, scientists can get a better grasp on just how populated the Edgeworth-Kuiper Belt is with asteroids, dwarf planets and rocks.
So now, rather than thinking that Edgeworth-Kuiper Belt objects are compilations of several small rocks, the New Horizons team thinks they were “born large”.
The last thing discovered by the team is Pluto’s bizarre collection of spinning moons. Spinning, spinning, spinning moons.
Rather than syncing up with Pluto – which is how our moon reacts to Earth, and indeed most moons react to their planetary parents – the smaller moons out there are spinning around like madmen.
Too much torque
Charon, the larger of the moons, exerts such a strong torque that it messes with their orbits and may even send them crashing into each other, thus creating Hydra.
“Pluto’s moons behave like spinning tops,” said co-investigator Mark Showalter of the SETI Institute in Mountain View, California.
“We suspect from this that Pluto had more moons in the past, in the aftermath of the big impact that also created Charon,” said Showalter.
Volcano image via Shutterstock