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— CH. 1 · DISCOVERY AND DETECTION —

Bright spots on Ceres

~3 min read · Ch. 1 of 6
6 sections

  • On the 9th of December 2015, scientists reported that the bright spots on Ceres may be related to a type of salt. The Dawn spacecraft identified these features during its orbital phase around the dwarf planet. Early in the mission, high albedo values sparked speculation about outgassing or ice deposits. These spots reflect light at an intensity four times greater than the average surface of Ceres. A cluster known as Spot 5 stands out within Occator crater at coordinates 19.86 degrees north latitude and 238.85 east longitude.

  • Spectroscopic data confirms the spots consist primarily of hydrated magnesium sulfate and sodium carbonate rather than pure ice. Near-infrared spectra reveal large amounts of sodium carbonate alongside smaller quantities of ammonium chloride or ammonium bicarbonate. Arizona State University researchers proposed that briny water erupted from the interior and sublimated to leave behind only the salt deposits. An informal NASA poll conducted in May offered ideas including ice, volcanos, geysers, salt deposits, rock, or other possibilities before consensus formed. Reflectivity studies from September 2015 suggest that the spots are probably salts rather than ice.

  • Scientists propose that briny water erupted from a deep interior reservoir and sublimated to leave behind salt deposits. 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. Further analysis indicates two sources: melting of crustal ices by impact and a deeper brine reservoir near or in the mantle. Hanami planum is a topographic high but a gravity low indicating isostatic compensation likely by buried ices.

  • The brightest cluster of spots known as Spot 5 is located within an crater called Occator at 19.86 degrees north latitude and 238.85 east longitude. The spot in the center of the crater is named Cerealia Facula while the group of spots to the east carries the name Vinalia Faculae. These names were approved by the International Astronomical Union on the 26th of November 2016. A haze fills around half of Occator crater without extending over its rim periodically appearing around Spot 5 adding credence to outgassing theories. Dimmer spots are located towards this crater's eastern rim while the largest component sits in the center.

  • Observations of transient hazes suggest recent or ongoing cryovolcanism releasing vapor into space from beneath the crust. A haze that fills around half of Occator crater does not extend over its rim and appears periodically around Spot 5. Andrew Rivkin noted in Sky & Telescope magazine that at low angles a haze can be seen inside but not outside of the crater. He speculated that this could be sublimated vapor from ice possibly linked to the bright spots. NASA confirmed in August 2020 that Ceres was a water-rich body with a deep reservoir of brine percolating to the surface causing the bright spots including those in Occator crater.

  • Dawn images led to widespread reports in media about the bright spots including news sources astronomy magazines and science magazines. An informal NASA poll during May offered ideas for the nature of the spots such as ice volcanos geysers salt deposits rock or other. 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. Articles appeared in outlets like Gizmodo and Sky & Telescope discussing the mystery before scientific consensus settled on salt deposits as the primary explanation.

Common questions

What are the bright spots on Ceres made of?

The bright spots on Ceres consist primarily of hydrated magnesium sulfate and sodium carbonate rather than pure ice. Spectroscopic data confirms these deposits formed when briny water erupted from the interior and sublimated to leave behind only the salt.

When did scientists report that the bright spots on Ceres may be related to a type of salt?

Scientists reported that the bright spots on Ceres may be related to a type of salt on the 9th of December 2015. Reflectivity studies from September 2015 suggest that the spots are probably salts rather than ice.

Where is Spot 5 located within Occator crater on Ceres?

Spot 5 stands out at coordinates 19.86 degrees north latitude and 238.85 east longitude within Occator crater. The spot in the center of the crater is named Cerealia Facula while the group of spots to the east carries the name Vinalia Faculae.

How were the names for the bright spots on Ceres approved by the International Astronomical Union?

These names were approved by the International Astronomical Union on the 26th of November 2016. The central spot received the name Cerealia Facula and the eastern group was designated Vinalia Faculae.

Why do hazes appear around Spot 5 in Occator crater on Ceres?

A haze fills around half of Occator crater without extending over its rim periodically appearing around Spot 5 adding credence to outgassing theories. Observations suggest recent or ongoing cryovolcanism releasing vapor into space from beneath the crust.

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All sources

29 references cited across the entry

  1. 1webNew Clues to Ceres' Bright Spots and OriginsElizabeth Landau — NASA — 9 December 2015
  2. 2webDeep freeze puts the squeeze on dwarf planet Ceres15 December 2015
  3. 3webMystery Solved: Bright Areas on Ceres Come From Salty Water BelowGretchen McCartney et al. — NASA — 10 August 2020
  4. 4newsMystery solved: Bright areas on Ceres come from salty water belowGretchen McCartney — 11 August 2020
  5. 5webUSGS: Ceres nomenclatureStaff — USGS — 13 July 2015
  6. 6webPlanetary Names: Crater, craters: Occator on CeresStaff — USGS — 6 July 2015
  7. 7inlineLPSC 2015: First results from Dawn at Ceres: provisional place names and possible plumes
  8. 8newsThe weird white spots on Ceres might not be ice after allRachel Feltman — July 10, 2015
  9. 9speechNow Appearing At a Dwarf Planet Near You: NASA's Dawn Mission to the Asteroid BeltMarc Rayman — 8 April 2015
  10. 10newsRecent Hydrothermal Activity May Explain Ceres' Brightest AreaElizabeth Landau et al. — NASA — 29 June 2016
  11. 11newsMistaken Identity: Ceres Mysterious Bright Spots Aren't Epsom Salt After AllSarah Lewin — 29 June 2016
  12. 12journalBright carbonate deposits as evidence of aqueous alteration on (1) CeresM. C. De Sanctis — 29 June 2016
  13. 13journalPreferential formation of sodium salts from frozen sodium-ammonium-chloride-carbonate brines – Implications for Ceres' bright spotsTuan H. Vu — July 2017
  14. 14journalFresh emplacement of hydrated sodium chloride on Ceres from ascending salty fluidsM De Sanctis et al. — 10 August 2020
  15. 15webA. Duffy – Cosmos – What on Ceres are those bright spots?
  16. 16webChris Russel at
  17. 17newsDawn at Ceres: A haze in Occator crater?Andrew Rivkin — The Planetary Society — 21 July 2015
  18. 19newsBright spotlight on Dawn mission to CeresJonathan Amos — BBC News — 2 March 2015
  19. 20webBright Spots on Ceres Intrigue ScientistsKelly Beatty — 3 March 2015
  20. 21webBright Spots on Ceres Could Be Active IceAlexandra Witze — 18 March 2015
  21. 22webWhat's the spot on World Ceres?Staff — NASA — 25 May 2015
  22. 23webWhat Are Those Bright Spots on Ceres? Go Vote!Calla Cofield — 22 May 2015
  23. 24inlineSky and Telescope magazine – Dawn Sees Ceres Bright Spots and More By Emily Poore July 30, 2015
  24. 25inlineCeres' Mysterious Bright Spots Aren't Made of Ice After All. Gizmodo, 1 October 2015
  25. 26journalImpact heat driven volatile redistribution at Occator crater on Ceres as a comparative planetary processP Schenk et al. — 2020
  26. 27journalA Possible Brine Reservoir Beneath Occator Crater: Thermal and Compositional Evolution and Formation of the Cerealia Dome and Vinalia FaculaeLynnae C. Quick et al. — 2019-03-01
  27. 28journalThe varied sources of faculae-forming brines in Ceres' Occator crater emplaced via hydrothermal brine effusionJ Scully et al. — 2020
  28. 29journalImpact-driven mobilization of deep crustal brines on dwarf planet CeresC Raymond et al. — 2020
  29. 30journalEvidence of non-uniform crust of Ceres from Dawn's high-resolution gravity dataR Park et al. — 2020