Bright spots on Ceres

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

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

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]

  1. ^ Staff (13 July 2015). "USGS: Ceres nomenclature" (PDF). USGS. Retrieved 16 July 2015.
  2. ^ 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.