“You are the salt of the earth. But remember that salt is useful when in association, but useless in isolation.” -Israelmore Ayivor

When NASA’s Dawn spacecraft began photographing Ceres, one big surprise emerged: the presence of a spectacularly and unusually bright spot at the bottom of Occator crater. As we got closer, we discovered it was a series of spots in the lowlands of the crater bed, and that there were other suspicious, smaller bright spots elsewhere on the surface.

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, converted from Nature Publishing Group press’s YouTube channel.

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, converted from Nature Publishing Group press’s YouTube channel.

The science is now in, and it’s not self-luminous, nor is it ice of any type, but rather these are salt crystals, deposited and brought to the bottom by water that solidifies on the crater floor.

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, from A. Natheus et al. (2015), Nature 528, 237–240.

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, from A. Natheus et al. (2015), Nature 528, 237–240.

Here’s the science of what we know, along with the new questions the discovery raises!

Comments

  1. #1 PJ
    Perth, west Oz
    December 9, 2015

    Yay !!! Got the salts right.
    As for OXO, it appears to be residing in a depression, ergo a similar process to Occator would be taking place.

  2. #2 Omega Centauri
    December 9, 2015

    wikipedia lists the escape velocity from Ceres as .51KM/sec. I’m guessing the speed of sound of water vapor is .2km/sec. The tail of the Maxwellian distribution of water vapor molecules ought to be well enough populated that the rate of leakage into interplanetary space ought to be pretty high. Do you really think the vapor is recondensing and washing salts into the depressions? Something akin to briny mudpots bubbling brine onto the surface would seem more intuitive. Is the subsurface temperature likely to be high enough for brine to be liquid?

  3. #3 Denier
    United States
    December 9, 2015

    @PJ #1

    I’m declaring victory on this one. Published May 19, 2015 proving that I can appropriate other people’s ideas and pass them off as my own with ridiculous speed.

  4. #4 PJ
    Perth, west Oz
    December 9, 2015

    @16 on that page, I did declare it to be salts, but not as we know it. My own educated guess without poaching someone elses work, naughty person. 😉

  5. #5 PJ
    Perth, west Oz
    December 16, 2015

    The closest spectroscopic analysis shows it is close to epsom salts.

  6. #6 Matt Galloway
    United States
    August 31, 2016

    Hmm do the great salt flats in the US glow in the middle of the night to the point they are visible from space? No. Yet the spots on Ceres still glow when Occator is in full night. There may be salt there but there is also energy of some sort emitting light. See PIA19584. MYSTERY UNSOLVED.

  7. #7 PJ
    Perth, west Oz
    August 31, 2016

    It was stated above the salts are not self-luminous, therefore do NOT glow in the dark.
    Nice fudged photo, though.
    🙂

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