Bright spots on Ceres

• 1. Discovery And Detection

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  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.

• 2. Chemical Composition Analysis

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  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.

• 3. Geological Formation Theory

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  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.

• 4. Occator Crater Specifics

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  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.

• 5. Ongoing Volcanic Activity

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  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.

• 6. Media And Public Reception

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  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.