Dawn spacecraft finds evidence of organic materials on Ceres
NASA’s Dawn spacecraft has detected evidence of organic materials on Ceres, a dwarf planet that is the largest object in the main asteroid belt between Mars and Jupiter. Researchers using Dawn’s visible and infrared mapping spectrometer (VIR) discover the material in and around a crater in Ceres’ northern hemisphere named Ernutet. Organic materials are of interest to scientists because they are necessary, but not sufficient, components of life on Earth.
Organic materials have previously been found inside certain meteorites and inferred from telescopic observations of certain asteroids. Ceres shares many attributes in common with meteorites rich in water and organics; in particular, a group of meteorites called carbonaceous chondrites. The discovery of organics on Ceres strengthens the connection between the dwarf planet, these meteorites, and their parent bodies.
“This is the first clear detection of organic molecules from orbit on a main belt body,” said Maria Cristina De Sanctis, lead author of the study, based at the National Institute of Astrophysics, Rome. The discovery is reported in the journal Science.
Data presented in the new study supports the idea that organic materials are native to Ceres. Carbonates and clays previously found on Ceres provide evidence for chemical activity in the presence of water and heat. It is possible that the organics were similarly produced in a warm, water-rich environment.
Essence of organics
The discovery of organics on Ceres adds to the ingredients found on the dwarf planet that are associated with life in the past. Previous studies have found hydrated minerals, carbonates, water ice, and ammoniated clays that must have been altered by water. Salts and sodium carbonate, such as those found in the bright areas of Occator Crater, are also thought to have been carried to the surface by liquid.
“This discovery adds to our understanding of the possible origins of water and organics on Earth,” said Julie Castillo-Rogez, Dawn project scientist based at NASA’s Jet Propulsion Laboratory in Pasadena, California.
Location of organics
The organic materials on Ceres are primarily located in an area covering approximately 400 square miles (about 1,000 square kilometers). A very strong signal of organics is visible on the floor of Ernutet Crater, on its southern rim and in an area to the southwest, just outside of the crater. There are smaller organics-rich areas several miles (∼11 kilometers) west and east of the crater. Organics were also located in a small portion of Inamahari Crater, approximately 250 miles (400 kilometers) from Ernutet.
Dawn’s VIR instrument was able to detect the organic material because of its special signature in near-infrared light. In enhanced, visible-light images taken by Dawn’s framing camera, the organic material associated with areas that appear redder than the rest of Ceres. The unique nature of these regions stands out even in low- resolution images from the VIR instrument.
“We’re still working on understanding the geological context for these materials,” said study co-author Carle Pieters, professor of geological sciences at Brown University, Providence, Rhode Island.
Continuation of mission
After completing nearly two years of observations at Ceres, Dawn is now in an extremely elliptical orbit of the dwarf planet, going for an altitude of 4,670 miles (7,529 kilometers) up to nearly 5,810 miles (9,350 kilometers). On February 23, Dawn will raise its orbit to approximately 12,400 miles (20,000 kilometers), about the same height as GPS satellites above Earth.
The spacecraft will also shift into a different orbital plane, allowing Dawn to study Ceres in a new geometry. In late spring, Dawn will view Ceres with the Sun directly behind the spacecraft, so that Ceres will appear brighter than before, possibly revealing more clues about its nature.
Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.