Not all talks at LPSC are about Mars. Monday, the highlight of the meeting was the exploration of all the places where oceans might exist beyond the Earth, and some of the oceans being discussed really made Earth feel like a dry desert world.

Let’s take a look at Pluto. Doctoral researcher Adeen Denton presented a new analysis of New Horizons images that hint at Pluto having a 150-km deep ocean beneath its icy crust. For comparison, the deepest point in the Earth’s ocean is the Challenger Deep in the Mariana Trench, which is just eleven kilometers deep.

These results are thanks to a new analysis of Pluto’s low-resolution side. During the New Horizon’s flyby, the mission got extremely good images on one side of Pluto and lower resolution images of Pluto’s other side while the mission was further away. There are a lot of tricks of the trade that allow folks to eek more information out of images, and over time, as our software gets better, we’re able to reprocess things and learn more. Well, in reprocessing the low-res side of Pluto, they found a fascinatingly located region with a fascinatingly disrupted-looking terrain.

That location? Exactly opposite from Sputnik Planum, the smooth heart-shaped region imaged in such amazing detail. Many researchers have proposed that Sputnik Planum is actually an impact basin. If this is the case, when Pluto was hit by whatever it was hit by, the impact would have generated shockwaves that traveled through and around the planet. On other planets, we have seen a crater on one side, and a disrupted terrain on the antipode – the opposite side – where the shock waves came together and tossed the land around. 

Different kinds of land, planetary core material, and stuff in-between can all transport these waves in different ways. Denton ran what she calls a “small army” of Pluto simulations that each had oceans of different thickness and cores of either serpentine or other materials that don’t matter because it was a core of serpentine and an ocean 150-km thick that produced the disruptions actually seen, we think, in the low-res images of Pluto.

Understanding the interplay of water, rock, and heat was a recurring theme throughout this meeting, and when it comes to the interplay of heat and ice, melting is a common result. This comes into particular play with Neptune’s moon Triton. Larger than Pluto, this captured Kuiper Belt Object had to somehow drop a ton of kinetic energy as it went from orbiting the Sun to orbiting Neptune. While this can partially be explained if Triton, like Pluto, was in a binary system with another large body, that doesn’t explain everything. 

Triton would have started in a highly elliptical orbit, going backward around Neptune, and that orbit would have become circularized over time through tidal effects that change the orbit while heating the world. Presented by Noah Hammond, new research finds that this process would have taken billions of years, and depending on the composition of Triton, potentially could have completely melted this world’s ice. In what was the sweetest analogy of the conference so far, researchers discussed how we can tell what is happening by comparing how the ice melted with how ice cream melts.

Specifically, think of how ice cream melts and spreads when placed on a hot pie. The top stays structured, but the entire surface spreads, and the edges change. All it will take to figure out if this is true is better images from a spacecraft. A mission named Trident is currently proposed, and if it is funded and makes it to Triton, its images of the meltiness will help us one day sort just what Triton is made of by looking at how it dissipated heat, like ice cream on a pie.

More Information

Antipodal Terrains Produced by Sputnik Planitia-Forming Impact Imply Pluto Has a Thick Ocean and Hydrated Core

Intense Geologic Activity on Triton for Billions of Years After Orbital Capture