Pluto may have two ice volcanoes that spew water ice, nitrogen, ammonia, and methane onto the dwarf planet’s surface, NASA announced today. The potential volcanoes were spied near Pluto’s South Pole, in images taken by NASA’s New Horizons spacecraft during its July flyby. NASA scientists used the photos to measure the mountains, they are several miles high and tens of miles wide, with large holes in their summits. “On Earth that generally means one thing a volcano,” said Oliver White, New Horizons postdoctoral researcher at NASA’s Ames Research Center. Scientists have seen cryovolcanoes like these before throughout our Solar System, especially on icy moons like Triton and Enceladus.
They’re just like the volcanoes here on Earth, but they spew melted, icy materials rather than piping hot magma. These frozen eruptions happen when heat builds up inside the core of a moon, usually, it’s the result of a host planet pushing and pulling on a moon, creating friction and heat. When the internal pressure is high enough, the volcanoes serve as a release valve, shooting out plumes that are a hundred or more degrees warmer than the frigid surface. But when these materials make it to the surface, they quickly freeze and solidify. Pluto’s not a moon that orbits another planet, though, so it’s not clear what the energy source is for its cryovolcanoes. There are a few ideas, though. One is that elements left over from when Pluto first formed more than 4 billion years ago may be radioactively decaying inside the dwarf planet, and warming things up in the process. Radioactive decay could also explain why Pluto looks to be a geologically active world. There are very few craters on the dwarf planet’s surface, meaning that somehow, the surface is moving and resurfacing itself over time. That hints at a possible energy source coming from inside Pluto.
Pluto isn’t the only thing puzzling scientists. Its moons behave pretty unexpectedly, too. Pluto has one large moon, Charon, and four smaller moons, Styx, Nix, Kerberos, and Hydra. Pluto and Charon actually orbit around each other because they are pretty similar in size. The four smaller moons spin wildly around the planetary system. Hydra, for example, rotates 89 times as it completes one trip around Pluto. The moons also wobble like “spinning tops,” thanks to the gravitational pulls of both Pluto and Charon. NASA thinks that the four wobbly moons are the results of mergers of two or more moons meaning Pluto once had even more satellites than it does now. New Horizons geologists combined images of Pluto’s surface to make 3-D maps that indicate two of Pluto’s most distinctive mountains could be cryovolcanoesice volcanoes that may have been active in the recent geological past. “It’s hard to imagine how rapidly our view of Pluto and its moons are evolving as new data stream in each week. As the discoveries pour in from those data, Pluto is becoming a star of the solar system,” said mission Principal Investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado. “Moreover, I’d wager that for most planetary scientists, any one or two of our latest major findings on one world would be considered astounding. To have them all is simply incredible.” The two cryovolcano candidates are large features measuring tens of miles or kilometers across and several miles or kilometers high. “These are big mountains with a large hole in their summit, and on Earth that generally means one thing a volcano,” said Oliver White, New Horizons postdoctoral researcher at NASA’s Ames Research Center in Moffett Field, California. “If they are volcanic, then the summit depression would likely have formed via collapse as material is erupted from underneath.
The strange hummocky texture of the mountain flanks may represent volcanic flows of some sort that have traveled down from the summit region and onto the plains beyond, but why they are hummocky, and what they are made of, we don’t yet know.” While their appearance is similar to volcanoes on Earth that spew molten rock, ice volcanoes on Pluto are expected to emit a somewhat melted slurry of substances such as water ice, nitrogen, ammonia, or methane. If Pluto proves to have volcanoes, it will provide an important new clue to its geologic and atmospheric evolution. Pluto’s surface varies in age from ancient, to intermediate, to relatively young according to another new finding from New Horizons. To determine the age of a surface area of the planet, scientists count crater impacts. The more crater impacts, the older the region likely is. Crater counts of surface areas on Pluto indicate that it has surface regions dating to just after the formation of the planets of our solar system, about four billion years ago.
But there also is a vast area that was, in geological terms, born yesterday meaning it may have formed within the past 10 million years. This area, informally named Sputnik Planum, appears on the left side of Pluto’s “heart” and is completely crater-free in all images received, so far. New data from crater counts reveal the presence of intermediate, or “middle-aged,” terrains on Pluto, as well. This suggests Sputnik Planum is not an anomaly that Pluto has been geologically active throughout much of its more than 4-billion-year history. “We’ve mapped more than a thousand craters on Pluto, which vary greatly in size and appearance,” said postdoctoral researcher Kelsi Singer, of the Southwest Research Institute (SwRI) in Boulder, Colorado. “Among other things, I expect cratering studies like these to give us important new insights into how this part of the solar system formed.” The New Horizons mission also is shedding new light on Pluto’s fascinating system of moons, and their unusual properties. For example, nearly every other moon in the solar system including Earth’s moon is in synchronous rotation, keeping one face toward the planet. This is not the case for Pluto’s small moons. Pluto’s small lunar satellites are spinning much faster, with Hydra its most distant moon rotating an unprecedented 89 times during a single lap around the planet. Scientists believe these spin rates may be variable because Charon exerts a strong torque that prevents each small moon from settling down into synchronous rotation.
Another oddity of Pluto’s moons, scientists expected the satellites would wobble, but not to such a degree. “Pluto’s moons behave like spinning tops,” said co-investigator Mark Showalter of the SETI Institute in Mountain View, California. Images of Pluto’s four smallest satellites also indicate several of them could be the results of mergers of two or more moons. “We suspect from this that Pluto had more moons in the past, in the aftermath of the big impact that also created Charon,” said Showalter.
For more information please visit: www.nasa.gov
Comments are closed.