One of the most prominent features of Pluto is Sputnik Planum, a flat landscape on the left side of the dwarf planet’s icy “heart.” Measuring about 745 miles across, it appears smooth and young. It is devoid of any impact craters that usually accumulate on older planetary surfaces. Two different studies published in the journal Nature indicate Pluto’s heart is beating, at least geologically.
Why Sputnik Planum looks so young
Images captured by New Horizons revealed a network of polygonal shapes that all rise in their centers. Prof Bill McKinnon from Washington University in St Louis, author of one of the studies, said the polygons could be the consequence of convection under Sputnik Planum, which is a huge reservoir of malleable nitrogen ice. Convection is like a slow motion bubbling.
Why does Sputnik Planum look perpetually youthful? Scientists said it’s because warm nitrogen ice continuously rises from under the Sputnik Planum. The fresh ice reaches the surface and spreads sideways to erase craters. Prof Bill McKinnon calculated that Sputnik Planum’s surface is completely repaved every 500,000 to 1 million years. It’s a surprisingly fast geological process. Researchers were not expecting this on a frigid planet that is about 40 times farther from the sun than Earth.
Radioactive elements in Pluto’s interior provide energy for convection
The temperature on Pluto’s surface is an extremely frigid -235 degrees Celsius. Since the planum ices also contain small amounts of methane and carbon monoxide, besides nitrogen, they are capable of flowing even at such a low temperature. The subsurface-convection requires a lot of energy. Scientists believe that decaying radioactive elements in Pluto’s interior produce the necessary energy to promote the continuous churning of nitrogen ice.
Alexander Trowbridge of Purdue University, author of the second study, explained convention as a process similar to a pot of oatmeal warming on the stove. The surface of the oatmeal separates into polygonal terrain. And the centers of the polygons rise slightly. As soon as you turn off the stove, the polygon center collapses. A similar process is active on Pluto’s Sputnik Planum, which creates the polygonal shape and help keep the region young.