Dawn observations indicate Ceres is geologically active
NASA’s Dawn spacecraft, which has been orbiting Ceres for three years, has observed changes on the dwarf planet’s surface indicating it is a dynamic, geologically active world. Two separate studies published in the journal Science Advances discuss these changes with one centering on the changing amounts of water ice and the other discussing the formation and distribution of carbonates.
The probe’s Visible and Infrared Spectrometer (VIR) found water ice in 12 sites on Ceres’ surface. According to NASA, a study showed these these concentrations were especially high in the northern wall of the 12-mile (20-kilometer) wide Juling Crater. Between April and October 2016, the level of water ice on that crater wall noticeably increased.
Andrea Raponi of the Institute of Astrophysics and Planetary Science (INAF) in Rome, who led the first study, said Dawn detected changes in the amount of exposed water ice on Ceres’ surface in many areas.
“This is the first direct detection of change on the surface of Ceres,” Raponi said in a NASA release. “The combination of Ceres moving closer to the Sun in its orbit, along with seasonal change, triggers the release of water vapor from the subsurface, which then condenses on the cold crater wall. This causes an increase in the amount of exposed ice. The warming might also cause landslides on the crater walls that expose fresh ice patches.”
Surface water ice on Ceres is stable in the long term only if it is in permanent shadow.
Led by Giacomo Carrozzo, also of the Institute of Astrophysics and Planetary Science, the second study used Dawn’s VIR to look at changes in Ceres’ crust and surface, specifically focusing on areas rich in sodium carbonates. According to NASA, these are abundant on the dwarf planet’s surface in bright areas such as Occator Crater, Oxo Crater, and Ahuna Mons, and formed within an ocean.
The dwarf planet is believed to have once harbored a subsurface ocean that could still exist today.
According to NASA, this discovery marks the first time hydrated carbonates have been found on any solar system body other than Earth. Interestingly, hydrated carbons last at most several million years before dehydrating.
“This implies that the sites rich in hydrated carbonates have been exposed due to recent activity on the surface,” Carrozzo said.
The diverse materials on Ceres’ surface, including water ice and carbonates, suggest the dwarf planet’s crust is not uniform. According to NASA, crustal variations could have been caused by the freezing of an underground ocean, impacting objects, or even cryovolcanism.
“Changes in the abundance of water ice on a short timescale, as well as the presence of hydrated sodium carbonates, are further evidence that Ceres is a geologically and chemically active body,”said Cristina de Sanctis, also of the Institute of Astrophysics and Planetary Science and VIR team leader.
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.