NASA’s audacious Pluto probe New Horizons has been a spectacular success by any standard.
After NASA’s New Horizons spacecraft arrived at Pluto back in July of last year, it spent the next three weeks carrying out a series of observations looking back at Pluto and its moons, slowing down only once in a while to send back low-bandwidth data regarding the solar wind and space dust it observed. However, well over 90% of the data that the probe had collected during its flyby, including most of the high-resolution imagery, remained out of reach for the time being, stored aboard the New Horizon’s digital recorders.
New Horizons reveals its trove of new data on Pluto
That all changed beginning in September, when New Horizons began returning gigabits of glorious data on Pluto. One photo showed the dwarf planet surrounded by a blue haze for a thousand miles above its surface. Astronomers had known Pluto had an atmosphere for a decade or so, but until now, the color and size of the atmosphere were not known.
Researchers have now also confirmed that Pluto is indeed a sphere. According to Francis Nimmo, a planetary scientist at the University of California, Santa Cruz, this likely means that dwarf planet had a relatively warm subsurface or even a liquid ocean. Astronomers know this because a planet of solid rock and ice, would have developed a bulge around its middle after billions ad billions of rotations, but Pluto has not.
The New Horizons team has been counting impact craters on Pluto’s surface in order to assist them in estimating the ages of various areas. Regions such as the pockmarked Cthulhu Regio show the signs of heavy meteor bombardment, and are likely very old; other areas are only moderately cratered and thus probably middle-aged; a few others, such as the smooth Sputnik Planum, are almost certainly young, just a few hundred million years old.
The notable geological diversity of the planetlet suggests it has been geologically active for much of its four-billion-year history, and also poses the the question of how these tectonic processes came about. It had been assumed that something as small and cold as Pluto could not have a molten core or liquid subsurface required for that kind of movement, but it is clear there has been plenty of geological action on Pluto. Two of the peaks on Pluto named Norgay Montes and Hillary Montes, are around eleven thousand feet tall, and their height and the steepness of their sides suggest that they may be composed of frozen water/ice. The New Horizons science team noted that the types of topographies observed would almost certainly require geological processes.
Also of note, the dwarf planet has two conical mountains with circular craters in the middle of them. Researchers suggest that these features are cryovolcanoes, that is, volcanoes that emit methane and nitrogen ice instead of molten rock like on Earth. Cryovolcanoes have also been found on Neptune’s largest moon Triton. Pluto’s surface is also dotted with so-called exotic ices, substances that become solid at much lower temperatures than water, and some of these structures show signs of glacial flow. Some of the high-resolution surface images also show a patch of glistening, blister-like bubbles covering the surface of Sputnik Planum. Astronomer Oliver White, of Ames, commented in a recent presentation at an American Astronomical Society conference, that these blisters may actually be water icebergs floating on a sea of glacially flowing nitrogen ice.
The only “disappointment” the New Horizons data has provided so far is that there is no sign that Pluto has any traces of a ring system. The system’s moons, however, are quite mysterious, with tiny Nix, Styx, Hydra, and Kerberos all having unusual orbits compared to most planetary moons.
Perhaps rthe best news for astronomers is that they have only received about half the data so far; it will be almost another year before they have retrieved the entire New Horizons data trove.