A recently released high-resolution swath of Pluto taken by NASA’s New Horizons spacecraft shows all kinds of wonderful things in Sputnik Planum, the informal name given to the icy plains dominating the left side of Pluto’s big “heart”. The strip reveals features less than half a city block in size
Sputnik Planum is at a lower elevation than most of the surrounding area by a couple of miles, but not completely flat. Its surface is separated into cells or polygons 10 to 25 miles wide (16-40 km), and when viewed at low sun angles, the cells are seen to have slightly raised centers and ridged margins, with about 100 yards (91.4 meters) of overall height variation.
Mission scientists believe the pattern of the cells stems from the slow thermal convection or churning of the nitrogen-dominated ices that fill Sputnik Planum. A reservoir that’s likely several miles or kilometers deep in some places, the solid nitrogen is warmed at depth by Pluto’s modest internal heat, becomes buoyant and rises up in great blobs, and then cools off and sinks again to renew the cycle.
“This part of Pluto is acting like a lava lamp,” said William McKinnon, deputy lead of the New Horizons Geology, Geophysics and Imaging team, from Washington University in St. Louis, “if you can imagine a lava lamp as wide as, and even deeper than, Hudson Bay.”
Computer models by the New Horizons team show that these blobs of overturning solid nitrogen can slowly evolve and merge over millions of years. The ridged margins, which mark where cooled nitrogen ice sinks back down, can be pinched off and abandoned.
The “X” feature is likely one of these – a former quadruple junction where four convection cells met. Numerous, active triple junctions can be seen elsewhere mosaic image strip.
In other much more local news, I wanted to let regular readers know I’ve been working on a book on a deadline. That’s the reason the blog may occasionally not get updated or otherwise suffer. The topic is naked eye astronomy — all the wonders you can see at night without any other equipment than eyeballs, a star map and flashlight. It’s set to come out in September. Thanks for your patience!