Reorientation of Sputnik Planitia implies a subsurface ocean on Pluto

Area of Science:

• Planetary Science
• Geophysics
• Astrobiology

Background:

• Sputnik Planitia on Pluto is a large, nitrogen-covered basin near the planet's tidal axis.
• Its current location suggests reorientation due to tidal and rotational forces.
• The basin presents a negative topography but requires a positive gravity anomaly for reorientation.

Purpose of the Study:

• To investigate the formation and current state of Sputnik Planitia.
• To determine the conditions necessary for the basin's observed gravity anomaly and location.
• To assess the role of a potential subsurface ocean in Pluto's geological evolution.

Main Methods:

• Analysis of gravitational anomalies and topographic data.
• Modeling of impact basin formation and planetary reorientation.
• Assessment of subsurface ocean dynamics and shell properties.

Main Results:

• A positive gravity anomaly in Sputnik Planitia is explained by shell thinning and ocean uplift, assuming an impact origin and a subsurface ocean.
• Without a subsurface ocean, an implausibly thick nitrogen layer would be required to explain the gravity anomaly.
• A rigid, conductive ice shell is necessary to maintain a long-lived subsurface ocean and its associated uplift.

Conclusions:

• The presence of a subsurface ocean is a likely explanation for Sputnik Planitia's characteristics.
• A subsurface ocean on Pluto could have persisted to the present day.
• Complex feedbacks between nitrogen deposition, loading, and planetary reorientation may have influenced Pluto's geological history.