Organic-rich materials found on Ceres by NASA’s Dawn orbiter are native to the dwarf planet, according to new research led by Southwest Research Institute planetary researcher Simone Marchi.
Dawn data show a region around Ceres’ Ernutet crater where organic concentrations have been discovered; the color coding shows the surface concentration of organics, as inferred from the visible and near infrared spectrometer; the inset shows a higher resolution enhanced color image of the crater acquired by Dawn’s framing camera; regions in red indicate higher concentration of organics. Image credit: NASA / JPL-Caltech / UCLA / ASI / INAF / MPS / DLR / IDA.
Ceres, the largest object in the main asteroid belt, is believed to have originated about 4.5 billion years ago at the dawn of the Solar System.
Studying its organics can help explain the origin, evolution, and distribution of organic species across our planetary system.
The very location of Ceres at the boundary between the inner and outer Solar System and its intriguing composition characterized by clays, sodium- and ammonium-carbonates, suggest a very complex chemical evolution.
The role of organics in this evolution is not fully understood, but has important astrobiological implications.
“The detection of localized, organic-rich material close to the Ernutet crater poses an interesting conundrum,” Dr. Marchi said.
“Was the organic material delivered to Ceres after its formation? Or was it synthesized and/or concentrated in a specific location on Ceres via internal processes?”
“Both scenarios have shortfalls, so we may be missing a critical piece of the puzzle,” he said.
Dr. Marchi and his colleagues the University of Chicago, Southwest Research Institute, and the Istituto Nazionale d’Astrofisica in Italy investigated the viability of organics delivery to Ceres via asteroidal and cometary impactors.
They explored a range of impact parameters, such as impactor sizes and velocities, using iSALE shock physics code simulations.
These models indicated that comet-like projectiles with relatively high impact velocities would lose almost all of their organics due to shock compression.
Impacting asteroids, with lower incident velocities, can retain between 20% and 30% of their pre-impact organic material during delivery, especially for small impactors at oblique impact angles.
However, the localized spatial distribution of organics on Ceres seems difficult to reconcile with delivery from small main belt asteroids.
“These findings indicate that the organics are likely to be native to Ceres,” Dr. Marchi said.
The researchers presented their results on October 18, 2017 at the 49th Meeting of the AAS Division for Planetary Sciences in Provo, Utah.
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Simone Marchi et al. 2017. On the origin of the organic-rich material on Ceres. 49th Meeting of the AAS Division for Planetary Sciences, abstract # 306.02
