New Horizons image shows where huge nitrogen ice blobs merged on Pluto's surface

The newest image of Pluto's ice fields offers a fascinating glimpse of what researchers believe is the movement of huge, solid nitrogen ice blobs on the surface of the distant dwarf planet.

Received by scientists from NASA's New Horizons spacecraft on Christmas Eve, the composite photo depicts part of the expansive icy plain that makes up the left side of Pluto's famous heart-shaped region. Sometimes called the Sputnik Planum, the plain consists of massive ice "blobs" — made up of solid but mobile nitrogen ice — that appear on Pluto's surface as amorphous shapes that rub against one another. 

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NASA scientists theorize that the blobs are a product of the convection of a kilometres-deep layer of nitrogen ice that rises and falls as it is heated from below by the dwarf planet's modest internal temperature. William McKinnon, deputy lead of NASA's New Horizons geology team, said in a news release that "this part of Pluto is acting like a lava lamp, if you can imagine a lava lamp as wide as, and even deeper than, the Hudson Bay."

Computer models show that over time the blobs change shape and even merge with neighbouring formations — and that's where the newest image gets interesting. 

In the bottom left corner of the composite photo, an "X" formation marks where four of the blobs likely met and eventually merged into one another, reinforcing prevailing theories about the nature of geologic activity in this region of Pluto.

You can explore the entire image, which captures an expanse 80 kilometres wide and 700 kilometres long and shows several other interesting surface features, here.

NASA also released an image of Pluto's so-called Viking Terra area this week.

The composite photo was created using images taken from two different cameras on board New Horizons and shows high concentrations of deep red tholins — aerosol particles that form through reactions in Pluto's atmosphere involving methane and nitrogen — in the bases of craters and in channels.

In thick deposits, tholins are generally considered immobile and it remains unclear how the particles are migrating to certain areas.

Researchers think the particles are being carried along by subsurface ice flows or blown around by Pluto's considerable winds, eventually settling in low lying regions. 

Check out a larger version of the composite image here.