Reorientation of Sputnik Planitia implies a subsurface ocean on Pluto

Abstract

The deep nitrogen-covered basin on Pluto, informally named Sputnik Planitia, is located very close to the longitude of Pluto's tidal axis and may be an impact feature, by analogy with other large basins in the Solar System. Reorientation of Sputnik Planitia arising from tidal and rotational torques can explain the basin's present-day location, but requires the feature to be a positive gravity anomaly, despite its negative topography. Here we argue that if Sputnik Planitia did indeed form as a result of an impact and if Pluto possesses a subsurface ocean, the required positive gravity anomaly would naturally result because of shell thinning and ocean uplift, followed by later modest nitrogen deposition. Without a subsurface ocean, a positive gravity anomaly requires an implausibly thick nitrogen layer (exceeding 40 kilometres). To prolong the lifetime of such a subsurface ocean to the present day and to maintain ocean uplift, a rigid, conductive water-ice shell is required. Because nitrogen deposition is latitude-dependent, nitrogen loading and reorientation may have exhibited complex feedbacks.

Thermal convection as a possible mechanism for the origin of polygonal structures on Pluto's surface

“…Overall, considering a 50% uncertainty on the initial results, leads to an ice layer thickness between 1.9 km and 8.5 km. Interestingly, this independent estimate agrees very well with our previous results and with previous estimates [ Trowbridge et al , ; Nimmo et al , ].…”

“…The exact ice layer thickness is, however, unknown. Assuming that Sputnik Planitia is located on a huge impact crater, as suggested by the formation mechanism proposed by Bertrand and Forget [], Nimmo et al [] propose an upper bound of about 7 km based on impact craters on the Moon and Iapetus, while Trowbridge et al [] suggest a minimum thickness of about 5 km in order to keep the observed icebergs afloat. On the basis of these estimates, we can only exclude ice layer thickness above 10 km.…”

Compaction and Melt Transport in Ammonia‐Rich Ice Shells: Implications for the Evolution of Triton

“…It is thought that tidal heating or convective upwellings may generate eutectic melting beneath chaos terrain on Europa (Sotin et al, 2002), and perhaps beneath double ridges on Europa (Nimmo & Gaidos, 2002). If the volatile-rich near-surface of an icy satellite is reheated, such as during a period of tidal heating or by the onset of solid-state convection in the ice shell, eutectic melts could be generated.…”

“…Many icy satellites and large Kuiper Belt objects are thought to harbor subsurface oceans of liquid water beneath ice shells that are tens to hundreds of kilometers thick (Hammond et al, 2013;Hussmann et al, 2006;Khurana et al, 1998;Kivelson et al, 2002;Nimmo et al, 2016;Postberg et al, 2009). Many icy satellites and large Kuiper Belt objects are thought to harbor subsurface oceans of liquid water beneath ice shells that are tens to hundreds of kilometers thick (Hammond et al, 2013;Hussmann et al, 2006;Khurana et al, 1998;Kivelson et al, 2002;Nimmo et al, 2016;Postberg et al, 2009).…”

“…Our solar system is overflowing with ocean worlds. Many icy satellites and large Kuiper Belt objects are thought to harbor subsurface oceans of liquid water beneath ice shells that are tens to hundreds of kilometers thick (Hammond et al, 2013;Hussmann et al, 2006;Khurana et al, 1998;Kivelson et al, 2002;Nimmo et al, 2016;Postberg et al, 2009). Potential regions of partial melt within the ice shells could be important in influencing the geological and thermal evolution of ocean worlds.…”