Organics found on dwarf planet Ceres

Scientists have spotted aliphatic organic molecules across a large swath of the dwarf planet Ceres (Science 2017, DOI: 10.1126/science.aaj2305). The compounds were likely produced on Ceres itself, suggesting that the rich chemistry needed to create life’s building blocks exists throughout the solar system.

An international team led by Maria Cristina De Sanctis at the National Institute of Astrophysics in Rome, examined spectra taken by NASA’s Dawn spacecraft, which has been orbiting Ceres since 2015. Ceres lies in the asteroid belt between Mars and Jupiter.

The team found organics in a 1,000-sq-km area near the crater Ernutet. Dawn’s spectrometer isn’t sensitive enough to identify individual molecules, but the spectra it captured suggest substances rich in aliphatic carbon, such as the mineral asphaltite and kerite, a rubberlike compound.

Scientists have observed extraterrestrial organics on some solar system bodies, such as comet 67P/Churyumov-Gerasimenko, Saturn’s moon Titan, and other asteroids. The new data from Ceres add another source of organics to the growing solar system list.

Sun Kwok, director of the Laboratory for Space Research at Hong Kong University, calls the work “exciting,” saying it confirms the widespread presence of complex organics in the solar system.

De Sanctis and her team also present evidence that the organics may have been produced on Ceres, rather than delivered via cometary impacts, a popular theory for how Earth was seeded with prebiotic compounds. The distribution of the organics across Ceres’s surface is broader than would be expected if they were generated by an impact, the researchers say. And the heat from such an impact would likely have destroyed the organics anyway.

The team hypothesizes that Ceres’s hydrothermal activity, combined with clay and ammonia-bearing hydrated minerals on the dwarf planet, produced the organics.

In a perspective accompanying the report, Michael Küppers at the European Space Agency notes that as a dwarf planet, Ceres may still harbor internal heat from its formation period and may even contain a subsurface ocean. “This opens the possibility that primitive life could have developed on Ceres itself,” he writes.