Plutonian Volcanoes

As New Horizons sets its course for the distant Kuiper Belt object 2014 MU69 (it'll get there on January 1, 2019), scientists are still learning one new thing after another about its encounter with Pluto.

Including that Pluto may be like Neptune's moon Triton in having volcanic mountains that occasionally erupt not with magma, but with ice. The two mountains near its south pole haven't been confirmed as "cryovolcanoes," but data available so far show a lot of similarities.

Cryovolcanoes happen when icy slush boils out of a mountain on a planet with a solid icy surface. Triton is regularly affected by Neptune's gravity, producing enough internal friction to create heat that makes the ice nearer the planet's core behave more like magma than like solid rock. As the surface shifts around the slush flows beneath it and sometimes bursts through at thin points near raised peaks.

Pluto lacks such a large nearby gravity source (Neptune its closest neighbor but is usually several million miles too far away to stress it that much), so if the two mountains are cryovolcanoes, the candidate list for the source of the heat is now being explored. The likely candidate is radioactivity in its core, as the elements from which Pluto was formed decay and emit heat in doing so.

It'll be interesting to see what other surprises our far-wandering friend produces as more and more New Horizons data is transmitted and studied.