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Starts With A Bang

Mostly Mute Monday: The Permanent Shadows of Ceres

The largest asteroid in the Solar System is hiding volatile materials that have never seen the Sun.

“Lots of science fiction deals with distant times and places. Intrepid prospectors in the Asteroid Belt. Interstellar epics. Galactic empires. Trips to the remote past or future.” –Edward M. Lerner

Most worlds in the Solar System, like our own, are significantly tilted as they orbit the Sun.

Image credit: NASA and Calvin J. Hamilton, 1999.

But Ceres, the Solar System’s largest asteroid, is a rare exception, like Mercury and Jupiter.

Image credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA, from the DAWN mission.

Inclined at only 3°, Ceres is so well-aligned that it possesses virtually no seasons, since its orbital eccentricity is small, too.

Image credit: Wikimedia Commons user Orionist, based on NASA data.

While we all wonder about the mysterious white spots in Occator crater, the polar regions offer a tantalizing possibility: permanent shadows.

Image credit: NASA DAWN mission / DLR / German Aerospace Center.

Ceres’ heavily cratered nature indicates an old surface, meaning that lava flows, oceans, or other resurfacing events haven’t occurred for billions of years.

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, via

But asteroids and comets can strike it from all angles, including at the poles.

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, of Ceres’ south pole, presently tipped away from the Sun.

If one of those craters is deep enough, and close enough to the pole itself, the small axial tilt means that sunlight never gets in.

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, of Ceres’ north pole, presently tipped towards the Sun, with permanently shadowed possiblities highlighted by E. Siegel.

At present, Ceres is tilted with its north pole slightly towards the Sun, showing us a number of possible candidates.

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, of Ceres’ north pole, false-colored to indicate topology.

The south pole is tipped away, with topographic maps leaving us wondering about tantalizing, shadowy hints.

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, of Ceres’ south pole, false-colored to indicate topology. The central region is blurred due to a lack of data, though half a Ceres-year in orbit will change that.

Frozen water, dry ice, even solid nitrogen could be present, thriving forever, just a few degrees above absolute zero.

Mostly Mute Monday tells the story of a single astronomical phenomenon or object in visuals, images, video and no more than 200 words.

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