Dawn’s closest views of Ceres show bright craters
Ceres’ Haulani Crater, with a diameter of 21 miles (34 kilometers), shows evidence of landslides from its crater rim. (Click to enlarge) Image & Caption Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
NASA’s Dawn spacecraft has provided scientists with spectacular close-up images of Ceres from its lowest mapping orbit of 240 miles (385 kilometers) above the dwarf planet’s surface. The images provide the best views so far of several craters and other features on Ceres. Haulani Crater, which has a diameter of 21 miles (34 kilometers), shows evidence of landslides from its crater rim. Smooth material and a central ridge stand out on the crater’s floor. An enhanced false-color image has given researchers new insight into materials and how they relate to surface morphology. This image shows rays of bluish material around the crater’s rim. In these images, the color blue has been associated with young features on Ceres.
“Haulani perfectly displays the properties we would expect from a fresh impact into the surface of Ceres. The crater floor is largely free of impacts, and it contrasts sharply in color from older parts of the surface,” said Martin Hoffmann, co-investigator on the Dawn framing camera team, based at the Max Planck Institute for Solar System Research, Göttingen, Germany.
Hualani is an unusually shaped crater with straight edges on its rim. Most craters on other planetary bodies, including Earth, are circular in shape. The straight edges of Haulani, and also some other craters on Ceres, are the result of pre-existing stress patterns and faults beneath the surface.
Oxo Crater is unique because of the relatively large “slump” in its crater rim. (Click to enlarge) Image & Caption Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI
Among the interesting features on the surface of Ceres are a number of bright spots which some scientists think may be salt deposits. The brightest cluster of these spots is in the center of a 57 mile (92-kilometer) crater called Occator. Dawn’s close-up view shows a dome in a smooth-walled pit in the bright center of the crater. Many linear features and fractures crisscross the top and flanks of the dome. Prominent fractures also surround the dome and run through smaller bright regions within the crater.
The second-brightest feature on Ceres is tiny Oxo Crater, which is only 6 miles (10 kilometers) wide. The small crater lies near the 0-degree meridian that defines the edge of many maps of Ceres. Oxo is also unusual because of the relatively large “slump” in its crater rim, where a mass of material has dropped below the surface. Dawn mission scientists are investigating the signatures of mineral on the crater floor, which appear different than elsewhere on Ceres.
“Little Oxo may be poised to make a big contribution to understanding the upper crust of Ceres,” said Chris Russell, principal investigator of the mission, based at the University of California, Los Angeles.
The Dawn spacecraft remains healthy in its lowest orbit around Ceres. It is taking new images and acquiring other data as it circles Ceres once every 5.4 hours.
Video courtesy of NASA
Jim Sharkey
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.
Has anyone considered the possibility that these “craters” may not have been formed by impacts? We all know that water expands when freezing. Conversely, ice contracts when melting. If a pocket of ice begins to melt just below the hard sealed crust of Ceres, then the crust above the pocket of water would be subjected to an inward force. As the ice melts below the surface of Ceres, a vapour region would likely form at the top section of the newly formed liquid water pocket. This vapour region might tend to erode the underneath side of the crust. As the crust thins locally and the water pocket grows, a section of the crust may eventually collapse or creep slowly inward, allowing the vapour from the water pocket to escape at the edges of the collapsing region. This would explain the shining streaks along the periphery or walls of the collapsed region. After collapse, the pocket of water may continue to grow causing further wall thinning of the central part of the collapsed region. Eventually the thin crust would crack allowing the vapour to escape from the water pocket. This would explain the salt deposits at the centre of the “crater”. I think this might be a more likely theory than impacts. There are several mechanisms available to explain why the ice pockets begin to melt in the first place.