New Horizons: Pluto may have ice volcanoes

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Wright Mons is located south of Sputnik Planum on Pluto NASA/JPL-JHU/SWRI

Two possible ice volcanoes have been identified on the surface of Pluto.

They are seen in images returned from the New Horizons probe, which flew past the dwarf planet in July.

The mountains are several km high and tens of km across, and each has what appears to be a depression in the top.

Unlike volcanoes on Earth that spew molten rock, Pluto’s volcanoes – if that is what they are – would likely release an icy slush of substances such as water, nitrogen, or methane.

The mission team still needs to do further work to confirm the discovery.

What would help in particular is information on the composition of the materials making up the local terrain.

Previous claims

However, New Horizons has not yet returned all its data from the flyby.

Only about 20% of its observations have been downlinked to Earth so far.

But if cryo-volcanism can be established it is an exciting discovery.

While the phenomenon has been postulated to occur on several outer Solar System bodies, nothing convincing has been detected.

The two candidates at Pluto are found just south of Sputnik Planum, the smooth plain on the planet’s equator.

They have been informally called Wright Mons and Piccard Mons.

On Earth or Mars, their shape recalls shield volcanoes – broad volcanoes that are built from repeat eruptions of low-viscosity fluids.

Mars analogy

As well as their putative calderas, they display a hummocky texture on their flanks that may represent old “lava” flows.

How recently they have been active, no-one can say currently.

“It’s just astounding that in all of the exploration that we have done, that the nearest neighbour analogy to these constructs occurs on Mars,” commented Prof Alan Stern, the principal investigator on the New Horizons mission.

“You have to look all the way to the other Red Planet to find something similar.

“Across all the worlds of the middle Solar System, we’ve seen nothing like this. It’s truly amazing.”

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