In other words, the massive accumulation of ice would end up where it causes the least wobble in Pluto's spin axis. If Sputnik Planitia were a large positive mass anomaly-perhaps due to loading of nitrogen ice-it would naturally migrate to Pluto's tidal axis with regard to Charon, Pluto's largest moon, as it approaches a minimum energy state, according to Keane and Matsuyama. And sure enough, in the models, the geographic location of Sputnik Planitia ended up suspiciously close to where one would expect it to be. The two researchers used observations made during New Horizons' flyby and combined them with computer models that allowed them to take a surface feature such as Sputnik Planitia, shift it around on the planet's surface and see what that does to the planet's spin axis. "I think this idea of a whole planet being dragged around by the cycling of volatiles is not something many people had really thought about before," Keane said. In a sense, Pluto is a (dwarf) planet whose shape and position in space are controlled by its weather. Eventually, over millions of years, it will drag the whole planet over." And if you have an excess of mass in one spot on the planet, it wants to go to the equator. "And once enough ice has piled up, maybe a hundred meters thick, it starts to overwhelm the planet's shape, which dictates the planet's orientation. "Each time Pluto goes around the sun, a bit of nitrogen accumulates in the heart," Keane said. Over the course of a Pluto year, nitrogen and other exotic gases condense on the permanently shadowed regions, and eventually, as Pluto goes around the sun, those frozen gases heat up, become gaseous again and re-condense on the other side of the planet, resulting in seasonal "snowfall" on Sputnik Planitia. At Pluto's lower latitudes near the equator, temperatures are almost as cold as minus 400 degrees Fahrenheit, cold enough to turn nitrogen into a frozen solid. Depending on the season, it's either one or the other, while Pluto's equatorial regions are extremely cold, all the time.īecause Pluto is almost 40 times farther from the sun than we are, it takes the little ball of rock and ice 248 Earth years to complete one of its own years. Therefore, the planet's poles get the most sunlight. To understand polar wander on Pluto, one first has to realize that unlike Earth, whose spin axis is only slightly tilted so that the regions around the equator receive the most sunlight, Pluto is like a spinning top lying on its side. For example, if a giant volcano were to grow on Los Angeles, the earth would reorient itself to place L.A. In short, this means that planets like to reorient to place any extra mass closer to the equator, and any mass deficits closer to the pole. Planets like to spin in such a way that minimizes energy. The second way is through true polar wander, where the spin axis remains fixed with respect to the rest of the solar system, but the planet reorients beneath it." "The first-and the one we're all most familiar with-is a change in the planet is a change in the planet's obliquity, where the spin axis of the planet is reorienting with respect to the rest of the solar system. "There are two ways to change the spin of a planet," Keane said. They propose evidence of frozen nitrogen pileup throwing the entire planet off kilter, much like a spinning top with a wad of gum stuck to it, in a process called true polar wander. 17 issue of Nature, these are the conclusions of research by James Keane, a doctoral student at the University of Arizona's Lunar and Planetary Laboratory, and his adviser, assistant professor Isamu Matsuyama. Sputnik Planitia, a 1,000-kilometer wide basin within the iconic heart-shaped region observed on Pluto's surface, could be in its present location because accumulation of ice made the dwarf planet roll over, creating cracks and tensions in the crust that point towards the presence of a subsurface ocean. Maps of Pluto and Charon by NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute. Video: This animation shows how Pluto reoriented in response to volatile ices filling Sputnik Planitia (the left lobe of Pluto's view moreĬredit: Animation by James Tuttle Keane.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |