{"id":15056,"date":"2016-11-24T21:30:36","date_gmt":"2016-11-24T13:30:36","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/study-shows-pluto-should-be-counted-among-solar-systems-ocean-worlds\/"},"modified":"2016-11-24T21:30:36","modified_gmt":"2016-11-24T13:30:36","slug":"study-shows-pluto-should-be-counted-among-solar-systems-ocean-worlds","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/study-shows-pluto-should-be-counted-among-solar-systems-ocean-worlds\/","title":{"rendered":"Study shows Pluto should be counted among solar system\u2019s ocean worlds"},"content":{"rendered":"
\"The
The expanse of Sputnik Planitia, the bright region visible in this image of Pluto, might cover an ocean of slushy water-ice. Credit: NASA\/JHUAPL\/SWRI<\/figcaption><\/figure>\n

Scientists believe they can explain how an ocean of water is lurking beneath an ice sheet inside Pluto\u2019s prominent heart-shaped region, an iconic frozen landscape discovered during the New Horizons spacecraft\u2019s flyby last year.<\/p>\n

A slushy buried sea under the icy plains of Sputnik Planitia would help counterbalance the gravitational weight of the dwarf planet\u2019s largest moon Charon, which stays fixed above the opposite side of Pluto, researchers reported last week in the journal Nature.<\/p>\n

Fed by computer model results and observations from New Horizons, the studies also present evidence that Pluto rolled over in the aftermath of a cataclysmic collision with a comet or another icy object that carved out the basin that became Sputnik Planitia, a 600-mile-wide (1,000-kilometer) feature that forms the left half of Pluto\u2019s bright heart.<\/p>\n

It turns out a mass of ice that filled Sputnik Planitia could have pulled Pluto off balance, re-orienting the dwarf planet to have the subsurface ocean facing almost perfectly away from Charon.<\/p>\n

\u201cThe New Horizons data say it\u2019s not only opposite Charon, but it\u2019s really close to being almost exactly opposite,\u201d said Richard Binzel, a co-investigator on the New Horizons mission from MIT. \u201cSo we asked, what\u2019s the chance of that randomly happening? And it\u2019s less than 5 percent that it would be so perfectly opposite. And then the question becomes, what was it that caused this alignment?\u201d<\/p>\n

It may be counterintuitive to think of Sputnik Planitia, a low-elevation plain surrounded by craggy mountain ranges, as a bulging bulk of mass capable of balancing the strong tidal tug from Charon.<\/p>\n

\u201cIt\u2019s a big, elliptical hole in the ground, so the extra weight must be hiding somewhere beneath the surface. And an ocean is a natural way to get that,\u201d said Francis Nimmo, professor of Earth and planetary sciences at the University of California, Santa Cruz.<\/p>\n

\"The
The geologic structure beneath the surface of Sputnik Planitia, which is believed to be an ancient impact basin that has since filled in with volatile ices. On Pluto, it is possible that the thinned crust is overlying a liquid water ocean. Credit: James Keane\/University of Arizona<\/figcaption><\/figure>\n

Nimmo was the lead author of a paper published Nov. 16 in Nature describing the new findings.<\/p>\n

The impact that formed Sputnik Planitia triggered an upwelling of water that pushed up against a weakened top layer of icy crust, Nimmo writes.<\/p>\n

\u201cAt that point, there is no extra mass at Sputnik Planitia,\u201d Nimmo said in a press release from UC Santa Cruz. \u201cWhat happens then is the ice shell gets cold and strong, and the basin fills with nitrogen ice. That nitrogen represents the excess mass.\u201d<\/p>\n

Pluto takes 248 Earth years to complete one trip around the sun in its distant, oblong orbit. That makes the dwarf planet\u2019s seasons last more than a half-century, and because Pluto spins on its side, its poles experience decades of direct sunlight and complete darkness each orbit, creating dramatic temperature extremes.<\/p>\n

Pluto\u2019s equatorial regions, including Sputnik Planitia, have more consistent temperatures, as low as minus 400 degrees Fahrenheit, or minus 240 degrees Celsius, cold enough to freeze nitrogen.<\/p>\n

As the seasons change on Pluto, nitrogen frozen on the surface heats up to become vapor, then travels through Pluto\u2019s tenuous atmosphere and falls as snow on Sputnik Planitia, adding more mass to the region.<\/p>\n

\u201cEach time Pluto goes around the sun, a bit of nitrogen accumulates in the heart,\u201d said James Keane, a doctoral student at the University of Arizona\u2019s Lunar and Planetary Laboratory who wrote a separate paper published in Nature last week outlining how Pluto rolled into its current orientation after the creation of Sputnik Planitia.<\/p>\n

\u201cOnce enough ice has piled up, maybe a hundred meters (330 feet) thick, it starts to overwhelm the planet\u2019s shape, which dictates the planet\u2019s orientation,\u201d Keane said in a story posted on the University of Arizona\u2019s website. \u201cAnd if you have an excess of mass in one spot on the planet, it wants to go to the equator. Eventually, over millions of years, it will drag the whole planet over.\u201d<\/p>\n

The fresh deposits of nitrogen snow and convective heat from the deep interior create fissures and cracks \u2014 fault lines \u2014 in the ice in Pluto\u2019s heart.<\/p>\n

Scientists lean toward the presence of an underground ocean to fully account for the mass clumped at Sputnik Planitia. Without an ocean there, the mass needed to align Sputnik Planitia with the location of Charon would require an \u201cimplausibly thick\u201d layer of nitrogen ice more than 25 miles (40 kilometers) thick, Nimmo wrote in Nature.<\/p>\n

\u201cWe tried to think of other ways to get a positive gravity anomaly, and none of them look as likely as a subsurface ocean,\u201d Nimmo said.<\/p>\n

So what is Pluto\u2019s hypothesized ocean like?<\/p>\n

\u201cPluto is small enough that it\u2019s just about almost cooled off but still has a little heat, and it\u2019s about 2 percent the heat budget of the Earth, in terms of how much energy is coming out,\u201d Binzel said in a story posted on MIT\u2019s website. \u201cSo we calculated Pluto\u2019s size with its interior heat flow, and found that underneath Sputnik Planitia, at those temperatures and pressures, you could have a zone of water-ice that could be at least viscous. It\u2019s not a liquid, flowing ocean, but maybe slushy. And we found this explanation was the only way to put the puzzle together that seems to make any sense.\u201d<\/p>\n

Email the author.<\/i><\/b><\/p>\n

Follow Stephen Clark on Twitter: @StephenClark1.<\/strong><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

The expanse of Sputnik Planitia, the bright region visible in this image of Pluto, might cover an ocean of slushy water-ice. Credit: NASA\/JHUAPL\/SWRI Scientists believe they can explain how an ocean of water is lurking beneath an ice sheet inside Pluto\u2019s prominent heart-shaped region, an iconic frozen landscape discovered during the New Horizons spacecraft\u2019s flyby […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[2],"tags":[1861,2173,2174,1561,2848,2612],"class_list":["post-15056","post","type-post","status-publish","format-standard","hentry","category-news","tag-jhuapl","tag-kuiper-belt","tag-new-horizons","tag-planetary-science","tag-pluto","tag-swri"],"acf":[],"_links":{"self":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/15056"}],"collection":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/comments?post=15056"}],"version-history":[{"count":0,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/posts\/15056\/revisions"}],"wp:attachment":[{"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/media?parent=15056"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/categories?post=15056"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/starpath.global\/blog\/wp-json\/wp\/v2\/tags?post=15056"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}