Wikipedia

Bright spots on Ceres

Several bright surface features (also known as faculae) were discovered on the dwarf planet Ceres by the Dawn spacecraft in 2015.

Cerealia and Vinalia Faculae stand out against the dark surface in Occator crater

The brightest cluster of spots ("Spot 5") is located in an 80-kilometer (50 mi) crater called Occator.[1][2] The largest and brightest component of the cluster is in the center of the crater, with dimmer spots located towards this crater's eastern rim. Early in the orbital phase of the Dawn mission, the high albedo of these spots was speculated to be due to some kind of outgassing,[3] and subsequent closer images helped scientists determine that it is a material with a high level of reflection, and suggested ice and salt as possibilities.[4] These bright features have an albedo of about 40%, four times brighter than the average of Ceres's surface.[5]

On 9 December 2015, scientists reported that the bright spots on Ceres may be related to a type of salt, particularly a form of brine containing hydrated magnesium sulfate (MgSO4·6H2O); the spots were also found to be associated with ammonia-rich clays.[6] Arizona State University scientists have proposed that the bright spots are best explained as resulting from briny water erupted from Ceres's interior that subsequently sublimated, leaving behind only the salt deposits.[7] Near-infrared spectra of these bright areas are consistent with a large amount of sodium carbonate, (Na
2CO
3) and smaller amounts of ammonium chloride (NH
4Cl) or ammonium bicarbonate (NH
4HCO
3). These materials have been suggested to originate from the recent crystallization of brines that reached the surface from below.[8][9][10][11] In August 2020, NASA confirmed that Ceres was a water-rich body with a deep reservoir of brine that percolated to the surface in various locations causing the "bright spots", including those in Occator crater.[12][13]

The bright material is only millions of years old; cryovolcanism may not have stopped completely as there is evidence of hydrated NaCl, and a thin haze, observed through variation in brightness, still present today, thought to be due to sublimating ice. Ice would not last long in such warm conditions exposed to the vacuum of space, so that would suggest it is being brought to the surface to this day.[14][15]

Spot 5

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Further information: Occator (crater)

The brightest cluster of spots ("Spot 5") is located in an 80-kilometer (50 mi) crater called Occator,[1][2] which is located at 19.86° N latitude; 238.85 E longitude.[1][2]

 
Spots on Ceres from different angles

The spot in the center of the crater is named Cerealia Facula,[16] and the group of spots to the east - Vinalia Faculae.[17] These names were approved by International Astronomical Union 26 November 2016.

Alan Duffy of Swinburne University suggested "a meteorite strike either shook covering material off the salty ice or heated it so that salty water rose to the surface as a geyser. The water escaped into space and now, only the salt remains."[18] A haze that fills around half of Occator crater and that does not extend over its rim[19] periodically appears around Spot 5, the best known bright spot, adding credence to the idea that some sort of outgassing or volcanism is occurring.[20][21]

Dawn's images led to widespread reports in the media about the bright spots, including in news sources,[22] astronomy magazines,[23] and science magazines.[24] An informal NASA poll during May offered the following ideas for the nature of the spots:[25] ice, volcanos, geysers, salt deposits, rock, or other.[26]

Asteroid specialist A. Rivkin noted, in an article by Sky & Telescope magazine, that at low angles a haze can be seen in but not outside of the crater, and speculated that this could be sublimated vapor from ice, possibly linked to the bright spots.[27]

Reflectivity studies from September 2015 suggest that the spots are probably salts rather than ice, implying that Ceres's interior is somehow delivering fresh salt to the surface.[28]

Further analysis of Dawn's low-altitude data indicates two sources: melting of crustal ices by impact, and a deeper brine reservoir (of sodium carbonate and/or ammonium chloride[29]),[30] near or in the mantle.[31][32][30] Hanami planum is a topographic high but a gravity low, indicating isostatic compensation, likely by buried ices.[29][33]

See also

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References

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  1. ^ a b c Staff (13 July 2015). "USGS: Ceres nomenclature" (PDF). USGS. Retrieved 16 July 2015.
  2. ^ a b c Staff (6 July 2015). "Planetary Names: Crater, craters: Occator on Ceres". USGS. Retrieved 16 July 2015.
  3. ^ LPSC 2015: First results from Dawn at Ceres: provisional place names and possible plumes
  4. ^ Feltman, Rachel (10 July 2015). "The weird white spots on Ceres might not be ice after all". The Washington Post. Retrieved 24 July 2015.
  5. ^ Rayman, Marc (8 April 2015). Now Appearing At a Dwarf Planet Near You: NASA's Dawn Mission to the Asteroid Belt (Speech). Silicon Valley Astronomy Lectures. Foothill College, Los Altos, CA. Retrieved 7 July 2018.
  6. ^ Landau, Elizabeth (9 December 2015). "New Clues to Ceres' Bright Spots and Origins". NASA. Retrieved 10 December 2015.
  7. ^ "Deep freeze puts the squeeze on dwarf planet Ceres". 15 December 2015.
  8. ^ Landau, Elizabeth; Greicius, Tony (29 June 2016). "Recent Hydrothermal Activity May Explain Ceres' Brightest Area". NASA. Retrieved 30 June 2016.
  9. ^ Lewin, Sarah (29 June 2016). "Mistaken Identity: Ceres Mysterious Bright Spots Aren't Epsom Salt After All". Space.com. Retrieved 30 June 2016.
  10. ^ De Sanctis, M. C.; et al. (29 June 2016). "Bright carbonate deposits as evidence of aqueous alteration on (1) Ceres". Nature. 536 (7614): 54–57. Bibcode:2016Natur.536...54D. doi:10.1038/nature18290. PMID 27362221. S2CID 4465999.
  11. ^ Vu, Tuan H.; Hodyss, Robert; Johnson, Paul V.; Choukroun, Mathieu (July 2017). "Preferential formation of sodium salts from frozen sodium-ammonium-chloride-carbonate brines – Implications for Ceres' bright spots". Planetary and Space Science. 141: 73–77. doi:10.1016/j.pss.2017.04.014. ISSN 0032-0633.
  12. ^ McCartney, Gretchen; JHautaluoma, Grey; Johnson, Alana (10 August 2020). "Mystery Solved: Bright Areas on Ceres Come From Salty Water Below". NASA. Retrieved 12 August 2020.
  13. ^ McCartney, Gretchen (11 August 2020). "Mystery solved: Bright areas on Ceres come from salty water below". Phys.org. Retrieved 12 August 2020.
  14. ^ Krummheuer, Birgit (6 March 2017). "Cryovolcanism on Dwarf Planet Ceres". Max Planck Institute for Solar System Research.
  15. ^ De Sanctis, M; Ammannito, E; Raponi, A; Frigeri, A; Ferrari, M; Carrozzo, F; Ciarniello, M; Formisano, M; Rousseau, B; Tosi, F.; Zambon, F.; Raymond, C. A.; Russell, C. T. (10 August 2020). "Fresh emplacement of hydrated sodium chloride on Ceres from ascending salty fluids". Nature Astronomy. 4 (8): 786–93. Bibcode:2020NatAs...4..786D. doi:10.1038/s41550-020-1138-8. S2CID 225442620.
  16. ^ "Cerealia Facula". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
  17. ^ "Vinalia Faculae". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
  18. ^ "A. Duffy – Cosmos – What on Ceres are those bright spots?". Archived from the original on 15 October 2015. Retrieved 15 June 2015.
  19. ^ "Chris Russel at". Archived from the original on 24 July 2015. Retrieved 25 July 2015.
  20. ^ Rivkin, Andrew (21 July 2015). "Dawn at Ceres: A haze in Occator crater?". The Planetary Society. Retrieved 24 July 2015.
  21. ^ Dawn at Ceres: A haze in Occator crater? Posted by Andrew Rivkin
  22. ^ Amos, Jonathan (2 March 2015). "Bright spotlight on Dawn mission to Ceres". BBC News. Retrieved 2 June 2015.
  23. ^ Beatty, Kelly (3 March 2015). "Bright Spots on Ceres Intrigue Scientists". Sky & Telescope. Retrieved 2 June 2015.
  24. ^ Witze, Alexandra (18 March 2015). "Bright Spots on Ceres Could Be Active Ice". Scientific American. Retrieved 2 June 2015.
  25. ^ Staff (25 May 2015). "What's the spot on World Ceres?". NASA. Archived from the original on 15 October 2015. Retrieved 25 May 2015.
  26. ^ Cofield, Calla (22 May 2015). "What Are Those Bright Spots on Ceres? Go Vote!". Space.com. Retrieved 25 May 2015.
  27. ^ Sky and Telescope magazine - Dawn Sees Ceres Bright Spots and More By Emily Poore July 30, 2015
  28. ^ Ceres' Mysterious Bright Spots Aren't Made of Ice After All. Gizmodo, 1 October 2015
  29. ^ a b Raymond, C; Ermakov, A; Castillo-Rogez, J; Marchi, S; Johnson, B; Hesse, M; Scully, J; Buczkowski, D (2020). "Impact-driven mobilization of deep crustal brines on dwarf planet Ceres". Nature Astronomy. 4 (8): 741–47. Bibcode:2020NatAs...4..741R. doi:10.1038/s41550-020-1168-2. S2CID 211137608.
  30. ^ a b Schenk, P; Scully, J; Buczkowski, D; Sizemore, H; Schmidt, B; Pieters, C; Neesemann, A; O'Brien, D (2020). "Impact heat driven volatile redistribution at Occator crater on Ceres as a comparative planetary process". Nature Communications. 11 (1): article 3679. Bibcode:2020NatCo..11.3679S. doi:10.1038/s41467-020-17184-7. PMC 7417549. PMID 32778649.
  31. ^ Quick, Lynnae C.; Buczkowski, Debra L.; Ruesch, Ottaviano; Scully, Jennifer E.C.; Castillo-Rogez, Julie; Raymond, Carol A.; Schenk, Paul M.; Sizemore, Hannah G.; Sykes, Mark V. (1 March 2019). "A Possible Brine Reservoir Beneath Occator Crater: Thermal and Compositional Evolution and Formation of the Cerealia Dome and Vinalia Faculae". Icarus. 320: 119–135. doi:10.1016/j.icarus.2018.07.016. S2CID 125508484.
  32. ^ Scully, J; Schenk, P; Castillo-Rogez, J; Buczkowski, D (2020). "The varied sources of faculae-forming brines in Ceres' Occator crater emplaced via hydrothermal brine effusion". Nature Communications. 11 (1): article 3680. Bibcode:2020NatCo..11.3680S. doi:10.1038/s41467-020-15973-8. PMC 7417532. PMID 32778642.
  33. ^ Park, R; Konopliv, A; Ermakov, A; Castillo-Rogez, J (2020). "Evidence of non-uniform crust of Ceres from Dawn's high-resolution gravity data". Nature Astronomy. 4 (8): 748. Bibcode:2020NatAs...4..748P. doi:10.1038/s41550-020-1019-1. S2CID 225387929.
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