Pluto’s mountains of ice surrounded by a sea of frozen nitrogen
Click for original image.
Cool image time! Though we only have a limited archive of high resolution pictures of Pluto that were taken when New Horizons did its close fly-by of the planet in July 2015, it is worthwhile sometimes to take a second look at some of those images. The picture to the right, cropped and annotated to post here, was taken during that July 14, 2015 fly-by, and shows a mountainous region dubbed Al-Idrisi Montes on the shore of a white frozen ocean. The red dotted line indicates a large trench that separates the Al-Idrisi mountains from the mountainous region to the west.
Sounds similar to an arctic shoreline here on Earth, doesn’t it? Not in the least. Those mountains, ranging from 600 to 9,000 feet high, are made of frozen ice, which on Pluto are as hard as granite due to the endless cold. And the white frozen ocean is frozen nitrogen, broken into polygon shaped blocks. Even stranger: those ice mountains might even be floating in that nitrogen sea! A paper from 2019 [pdf] looked at the New Horizons data and concluded as follows:
Evidence suggests that the Al-Idrisi mountains may have been uplifted by the formation of
the western trench feature. Solid state convection appears to be our best supposition as to how the Al-Idrisi Montes reached their heights.
In other words, as that large trench/depression formed, convection (the bubbles you see when you simmer tomato sauce) pushed these mountains of ice upward to float above the “sea level” of that nitrogen sea.
At least, that’s one hypothesis. The scientists who wrote this paper admit their “our hypothesis still remains in need of study and this trench-mountain system warrants serious further research.” In other words, we simply don’t know enough to have a definitive understanding of the geology of this extremely alien planet.
