Ceres' surface features were likely created by interior activity

Freezing of internal ocean and impacting objects are unlikely to have created chains of pits.
By Laurel Kornfeld | Nov 11, 2017
Ceres' surface features, such as chains of pits and secondary craters, were likely created by the movement of materials in the dwarf planet's interior as far back as one billion years ago, according to a new study of data returned by NASA's Dawn mission.

Secondary craters are are formed from materials ejected out of larger craters. They often appears in clusters surrounding primary craters produced by impacts.

Linear features are those that appear linear on a map, including ditches, streams, tracks, etc.

In the most recent study, scientists on the Dawn mission produced a map showing more than 2,000 linear features 0.6 miles or longer located near primary craters.

Upon analyzing these features, the scientists successfully divided them into two categories. The first and most common category are chains of secondary craters, strings of round, sunken areas created by materials that primary craters ejected.

Less common are chains of pits, which are created by fractures beneath the surface.

Both types of linear features look similar; however, pit chains tend to be irregular and lack raised rims while secondary crater chains are more round and usually surrounded by rims.

Because the pit chains are created by interior rather than exterior activity, they alone can inform scientists as to the interior evolution of the dwarf planet.

Findings of the study support the theory that hundreds of millions to a billion years ago, subsurface materials within Ceres welled upward toward the surface, in the process fracturing the crust.

"As this material moved upward from underneath Ceres' surface, portions of Ceres' outer layer were pulled apart, forming the fractures," explained science team associate Jennifer Scully of NASA's Jet Propulsion Laboratory in California.

Subsurface material may have been less dense than the material surrounding it, causing the former to well up, forming the pit chains.

Other possible scenarios to which Ceres' surface features could be attributed are less likely. Freezing of a subsurface ocean would have caused pit chains to be scattered evenly across Ceres's surface, which is not the case.

Had an impacting object caused the surface fractures, the impactors would have been large and left behind evidence, none of which is present on the small planet.

Further research will use computer models to test whether and how interior upwelling could have occurred near the fractures.

Findings of the study, whose lead author is Scully, have been published in the journal Geophysical Research Letters.

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