{"id":15808,"date":"2020-06-23T13:43:17","date_gmt":"2020-06-23T12:43:17","guid":{"rendered":"https:\/\/ounews.co\/?p=15808"},"modified":"2020-06-23T13:43:17","modified_gmt":"2020-06-23T12:43:17","slug":"life-inside-pluto-hot-birth-may-have-created-internal-ocean-on-dwarf-planet","status":"publish","type":"post","link":"https:\/\/www.open.ac.uk\/blogs\/news\/science-mct\/life-inside-pluto-hot-birth-may-have-created-internal-ocean-on-dwarf-planet\/","title":{"rendered":"Life inside Pluto? Hot birth may have created internal ocean on dwarf planet"},"content":{"rendered":"

David Rothery<\/a>, Professor of Planetary Geosciences at The Open University<\/a>, discusses what it means to discover internal oceans on Pluto and other planets in the solar system.<\/p>\n

Pluto, along with many other dwarf planets in the outer solar system, is often thought of as dark, icy and barren \u2013 with a surface temperature of just \u2212230\u00b0C. But now a new study,\u00a0published in Nature Geoscience<\/a>, suggests that the body has had a warm interior ever since it formed, and may still have a liquid, internal ocean under its icy crust.<\/p>\n

It could mean that other sizeable icy dwarf planets may have had early internal oceans too, with some possibly persisting today. This is exciting, as where there\u2019s warm water, there could be life.<\/p>\n

\"\"
Near-sunset view of Pluto\u2019s rugged, icy mountains and flat plains.<\/span>\u00a0NASA\/Johns Hopkins University Applied Physics Laboratory\/Southwest Research Institute<\/a><\/span><\/figcaption><\/figure>\n

As soon as NASA\u2019s New Horizon\u2019s probe began to send back its haul of pictures and other data from its\u00a02016 flyby of Pluto<\/a>, it became clear that this is\u00a0one of the most interesting worlds<\/a>\u00a0ever seen. Beneath its haze-layered atmosphere is a frigid, cratered surface of impure water-ice and one major impact basin (Sputnik Planitia) that has been flooded by frozen nitrogen.<\/p>\n

The water-ice crust is cut by numerous fractures, all of which appear to be the result of stretching of the surface. Those cracks in the ice provided the first hints that there might be liquid water flowing underneath, in the form of an internal ocean between the icy shell and rocky core. More evidence\u00a0soon emerged<\/a>\u00a0in favour of this, such as hints that the icy shell has been able to re-orient itself, gliding over an essentially frictionless (hence liquid) interior.<\/p>\n

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Artist\u2019s impression showing Pluto\u2019s interior. An ocean of liquid water between the icy crust and rocky core.<\/span>\u00a0Pam Engebretson\/Physics Org<\/span><\/span><\/figcaption><\/figure>\n

If it does have an internal ocean, Pluto is far from unique. Evidence for present-day oceans inside icy moons such as Jupiter\u2019s\u00a0Europa<\/a>, and Saturn\u2019s\u00a0Titan<\/a>\u00a0and\u00a0Enceladus<\/a>\u00a0is so strong that few scientists doubt the likelihood of an ocean inside Pluto for at least part of its history.<\/p>\n

Cracking time<\/h2>\n

The insight offered by the new study comes from studying maps of Pluto\u2019s shape and features. The researchers discovered that cracks in its surface are of all ages \u2013 right back to the most remote times we can see, soon after the surface formed, possibly 4.5 billion years ago.<\/p>\n

Scientists have assumed that Pluto grew by slowly accumulating icy material that condensed when the outer solar system was forming. In such a scenario, no internal ocean could have formed until trapped heat generated by radioactive decay in the rocky core had built up sufficiently to melt the overlying ice.<\/p>\n

In that situation, the oldest geological faults on the surface would have certain specific characteristics (dubbed\u00a0compressional features<\/a>). This is because turning the lower part of the ice into liquid water, which is denser and occupies less volume, would have placed the overlying ice into compression.<\/p>\n

Other types of fractures interpreted as \u201cextensional cracks<\/a>\u201d could begin to form only when the top of this ocean began to freeze as its heat escaped to space. The pressure of the ice forced the interior to expand slightly, stretching and cracking the surface a little. However, Pluto\u2019s surface is cut by what appear to be extensional cracks only, right back to the most ancient times.<\/p>\n

\"\"<\/a><\/p>\n
<\/div>
Part of a map of Pluto\u2019s topography (dark = low, bright = high). The dark (low) area in the east is part of Sputnik Planitia. Ancient north-south troughs run to its west; more obvious narrower and younger cracks run obliquely.<\/span>\u00a0Paul Schenk<\/span><\/span><\/figcaption><\/figure>\n

The authors therefore argue that the young Pluto grew to its present size by accumulating tiny pieces of material in a so-called \u201cpebble accretion\u201d process that was energetic and rapid enough to cause melting at the base of the ice layer. This is termed a \u201chot start\u201d, though all it means is \u201cjust warm enough for water-ice to melt\u201d.<\/p>\n

The crust, from the first moment that it became stable, never experienced compression. Instead, its surface suffered extension as liquid water at top of the ocean froze onto the base of the ice shell during Pluto\u2019s first half billion years.<\/p>\n

Ocean freezing may then have paused for about the next billion years because the build-up of radioactive heat was temporarily able to balance the rate of heat escape to space. But ever since then, as Pluto\u2019s radioactive heat production dwindled over time, the roof of the ocean continued to freeze. The thickness of the ice shell has maybe doubled to about 180km. The surviving ocean is likely a 200km thick layer between the ice and the rock.<\/p>\n

Oceans and life<\/h2>\n

Internal oceans are fascinating, not just because of how changes in volume can stretch or compress the surface, but because they are potential habitats for life. It is irrelevant that Pluto\u2019s surface temperature is extremely low, because any internal ocean would be warm enough for life.<\/p>\n

This could not be life depending on sunlight for its energy, like most life on Earth, and it would have to survive on the probably very meagre chemical energy available within Pluto. So while we can\u2019t rule out there could be life inside Pluto, Europa and Enceladus are likely to be better contenders, since they have\u00a0more chemical energy available<\/a>.<\/p>\n

David Rothery<\/a>, Professor of Planetary Geosciences, The Open University<\/em><\/a><\/p>\n

This article is republished from\u00a0The Conversation<\/a>\u00a0under a Creative Commons license. Read the\u00a0original article<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

David Rothery, Professor of Planetary Geosciences at The Open University, discusses what it means to discover internal oceans on Pluto and other planets in the solar system. Pluto, along with many other dwarf planets in the outer solar system, is often thought of as dark, icy and barren \u2013 with a surface temperature of just […]<\/p>\n","protected":false},"author":19,"featured_media":15812,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[14,16],"tags":[861,1065,1525,1640,1643,1794,2115,2200],"class_list":["post-15808","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-science-mct","category-space","tag-faculty-of-stem","tag-higher-education","tag-news-home","tag-ou-home","tag-ou-news","tag-professor-david-rothery","tag-stem","tag-the-conversation"],"_links":{"self":[{"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/posts\/15808","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/users\/19"}],"replies":[{"embeddable":true,"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/comments?post=15808"}],"version-history":[{"count":0,"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/posts\/15808\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/media\/15812"}],"wp:attachment":[{"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/media?parent=15808"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/categories?post=15808"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.open.ac.uk\/blogs\/news\/wp-json\/wp\/v2\/tags?post=15808"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}