Long-term Evolution of Sputnik Planitia: Cryo-clastic Eruptions and their Implications
Abstract
The Sputnik Planitia (SP) impact basin [1] on Pluto is currently the location of an extensive deposit of volatile ices of N2, CO and CH4 [2]. Those ices are undergoing solid-state convection as evidenced by the organization of surface features into cellular structures tens of kilometers across [3, 4]. SP is a positive mass anomaly that migrated to its current position after a process of and sub-basin crustal thinning and volatile infilling [1, 5]. This scenario neglects the potentially important effects of endogenic heat flow, especially as might be enhanced due buried heat from the impact. Such upward heat flow would delay infilling of SP with volatile ices, and could result in interspersed episodes of infilling and removal of volatile material. The volatile ices would form an insulating layer, and the basal temperature (and corresponding vapor pressure of the N2 ice) would increase as the layer depth increased. For a heat-flow enhancement of just 5x over present-day endogenic heat flow, the vapor pressure of N2 will exceed the overburden stress at depths less than 1km. Such overpressure at the base of a nascent SP volatile-ice layer would lead to geyser-like activity and depletion of the volatiles. Later, thicker ice layers could perhaps effectively confine the N2 vapor. Truly violent releases of material could result, yielding episodic increases in atmospheric bulk, and transport of liquid and solid material entrained in the gas flow (what might be termed a "cryo-clastic" eruption mechanism). Such eruptions would be significantly supersonic and have significant horizontal velocity components. As a result, the flows could travel ballistically over distances comparable to Pluto's radius before falling back to the surface. Geomorphic signatures should result, although examples of the resulting landforms may not exist on the other explored bodies of the solar system. One Plutonian landform that might have been formed via this mechanism is the bladed terrain of Tartarus Dorsa. References [1] Nimmo et al., Nature v540 (2016). [2] Grundy et al., Science v351 (2016). [3] Stern et al., Science v350 (2015). [4] McKinnon et al., Nature v534 (2016). [5] Keane et al., Nature v540 (2016).
- Publication:
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AAS/Division for Planetary Sciences Meeting Abstracts #50
- Pub Date:
- October 2018
- Bibcode:
- 2018DPS....5050607S