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CURRENT DRAFT: Geology of Pluto rewrite

High-resolution New Horizons image showing the chaotic, blocky Al-Idrisi Montes near the western fringes of Sputnik Planitia's convecting glaciers

The geology of Pluto consists of the characteristics of the surface, crust, and interior of the dwarf planet Pluto. With a mean diameter of 2,376.6±1.6 km, Pluto is the largest known object beyond Neptune and the largest known dwarf planet in the Solar System, though Eris is significantly more massive. Pluto's density of 1.85 g/cm3 indicates that Pluto is composed of a significant amount of water, [1] differentiated into an outer icy crust and a probable internal ocean of liquid water that surrounds a rocky core. More volatile compounds such as nitrogen, methane, and ammonia cover much of Pluto's surface, shaping and eroding its terrain. These volatiles also sublimate into Pluto's thin atmosphere, driving weather and climate.

Because of Pluto's great distance from Earth, many details about Pluto remained unknown until 14 July 2015, when the New Horizons spacecraft flew through the Pluto system and began transmitting data back to Earth. When it did, Pluto was found to have remarkable geologic diversity, with New Horizons team member Jeff Moore saying that it "is every bit as complex as that of Mars". [2] The final New Horizons Pluto data transmission was received on 25 October 2016. [3]

Geological history

Pluto is a member of the Kuiper belt, an extensive disk of debris which survived the formation of the Solar System. As such, Pluto's formation and history is closely tied to other Kuiper belt objects (KBOs). Prior to the flyby of New Horizons, the nature of Pluto's formation was unclear and debated. Models of Pluto's early history can be divided into hot start and cold start models. Hot start models advocate for a rapid and violent formation which led to an initial era of rapid internal expansion and an ongoing era of more gradual expansion as Pluto's internal ocean freezes. Cold start models, in contrast, advocate for a slower, more gradual formation; Pluto's internal ocean only formed once enough radiogenic heat built up, leading to an initial era of compression as part of its icy mantle melts. [4]

stuff about pluto's faults being extensional wawawawawa

Initial models of KBO formation predicted very slow growth, taking hundreds of millions of years to create Pluto-sized objects, conflicting with the hot start scenario. More recent models, however, suggest that streaming instability in the Solar protoplanetary disc initiated a very rapid era of accretion into Pluto-sized objects, taking less than 100,000 years to grow planetesimals from ~300 km in diameter to ~1,000 km in diameter. This rapid accretion stage is in agreement with a hot start scenario, and a delayed-onset (after significant amounts of 26Al decayed) rapid accretion stage additionally reconciles the differentiated nature of dwarf planets such as Pluto and the porous, poorly-differentiated nature of smaller KBOs. [4]

Charon impact

Pluto hosts a system of five satellites; Charon, the largest moon of Pluto and roughly half its size, is massive enough that the system's barycenter lies well outside of Pluto. Four smaller circumbinary moons revolve around Pluto and Charon. Charon and the outer moons are thought to be the result of a giant impact between two large similarly-sized planetesimals early in the Solar System's history, likely before Neptune and Uranus began migrating outwards. Following the giant impact, Pluto was likely left rapidly rotating, whilst Charon may have followed a highly-eccentric orbit. The energy from the giant impact would have heated Pluto intensely, possibly raising its global temperature by 50-75K; tidal heating from Charon as its orbit around Pluto dampened would have imparted additional heat. By the end of Charon's orbital evolution around Pluto, both worlds would likely have been differentiated. [5]

Surface

Pluto's surface is highly diverse. Pluto is a reflective object, average Bond albedo of 0.72, [6] [a] but its surface is unusually contrastive in color, with Marc Buie comparing the level of contrast on Pluto to Saturn's moon Iapetus. [8]

Polar caps

Pluto's higher latitudes are largely covered in a layer of deposited soft ice, which forms its extensive polar ice caps.

Dark maculae

Sputnik Planitia

Main article: Sputnik Planitia

Sputnik Planitia is a massive elliptical depression located near Pluto's anti-Charon point.

Western Sputnik mountains

Along the western edges of Sputnik Planitia lie an extensive series of mountain ranges.

Western plains

Eastern plains

Hummocky terrain

Bladed terrain

Tectonics and faults

Ridge-trough system

A great, ancient tectonic system of troughs, plateaus, and mountain ranges hundreds of kilometers wide termed the ridge-trough system (RTS) cuts a roughly north to south great circle around Pluto, following between the 145°-165° E meridians. The RTS is extends for at least 3,200 kilometers across Pluto's surface and is 300 to 400 kilometers wide for much of its length, though it appears to extend further south into the unimaged regions of Pluto and a large section is interrupted by the Sputnik Planitia basin. [9]: 422  That it is so significantly eroded and superceded by the Sputnik Planitia basin indicates that it is the oldest large-scale feature identified on Pluto's surface.

Sputnik-related faults

Cryovolcanism

Hyecho Palus

Internal structure

Subsurface ocean

See also

References

  1. ^ Stern, S.A.; Grundy, W.; McKinnon, W.B.; Weaver, H.A.; Young, L.A. (2017). "The Pluto System After New Horizons". Annual Review of Astronomy and Astrophysics. 2018: 357–392. arXiv: 1712.05669. Bibcode: 2018ARA&A..56..357S. doi: 10.1146/annurev-astro-081817-051935. S2CID  119072504.
  2. ^ "New Pluto images from NASA's New Horizons show complex terrain". Astronomy. 10 September 2015. Retrieved 29 June 2018.
  3. ^ "Pluto Exploration Complete: New Horizons Returns Last Bits of 2015 Flyby Data to Earth". Johns Hopkins Applied Research Laboratory. 27 October 2016. Retrieved 3 December 2016.
  4. ^ a b Bierson, Carver J.; Nimmo, Francis; Stern, S. Alan (June 2020). "Evidence for a hot start and early ocean formation on Pluto". Nature Geoscience. 13 (7): 468–472. Bibcode: 2020NatGe..13..468B. doi: 10.1038/s41561-020-0595-0.
  5. ^ Moore, Jeffrey M.; McKinnon, William B. (May 2021). "Geologically Diverse Pluto and Charon: Implications for the Dwarf Planets of the Kuiper Belt". Annual Review of Earth and Planetary Sciences. 49. Bibcode: 2021AREPS..49..173M. doi: 10.1146/annurev-earth-071720-051448.
  6. ^ Williams, David R. (24 July 2015). "Pluto Fact Sheet". NASA. Archived from the original on 19 November 2015. Retrieved 6 August 2015.
  7. ^ Williams, David R. (16 March 2017). "Earth Fact Sheet". NASA/Goddard Space Flight Center. Retrieved 26 July 2018.
  8. ^ Buie, Marc W. "Pluto map information". Archived from the original on June 29, 2011. Retrieved February 10, 2010.
  9. ^ Schenk, P. M.; Beyer, R. A.; McKinnon, W. B.; Moore, J. M.; Spencer, J. R.; White, O. L.; Singer, K.; Nimmo, F.; Thomason, C.; Lauer, T. R.; Robbins, S.; Umurhan, O. M.; Grundy, W. M.; Stern, S. A.; Weaver, H. A.; Young, L. A.; Smith, K. E.; Olkin, C. (November 2018). "Basins, fractures and volcanoes: Global cartography and topography of Pluto from New Horizons". Icarus. 314: 400–433. Bibcode: 2018Icar..314..400S. doi: 10.1016/j.icarus.2018.06.008. S2CID  126273376.
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