Occator Crater, measuring 57 miles (92 kilometers) across and 2.5 miles (4 kilometers) deep, contains the brightest area on Ceres. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI
Scientists from NASA’s Dawn mission unveiled new images from the spacecraft’s lowest orbit at Ceres, including highly anticipated views of Occator Crater, at the 47th annual Lunar and Planetary Science Conference in The Woodlands, Texas, on Tuesday. Occator Crater, measuring 57 miles across and 2.5 miles deep, contains the brightest area on Ceres, the dwarf planet that Dawn has explored since early 2015. The latest images, taken from 240 miles above the surface of Ceres, reveal a dome in a smooth-walled pit in the bright center of the crater. Numerous linear features and fractures crisscross the top and flanks of this dome. Prominent fractures also surround the dome and run through smaller, bright regions found within the crater.
Ralf Jaumann, planetary scientist said: “The intricate geometry of the crater interior suggests geologic activity in the recent past, but we will need to complete detailed geologic mapping of the crater in order to test hypotheses for its formation.” The team also released an enhanced color map of the surface of Ceres, highlighting the diversity of surface materials and their relationships to surface morphology. Ceres does not have as many large impact basins as scientists expected, but the number of smaller craters generally matches their predictions. The blue material highlighted in the color map is related to flows, smooth plains and mountains, which appear to be very young surface features.
Ceres’ Haulani Crater (21 miles, 34 kilometers wide) is shown in these views from the visible and infrared mapping spectrometer (VIR) aboard NASA’s Dawn spacecraft. Credits: NASA/JPL-Caltech/UCLA/ASI/INAF
“Although impact processes dominate the surface geology on Ceres, we have identified specific color variations on the surface indicating material alterations that are due to a complex interaction of the impact process and the subsurface composition,” Jaumann said. “Additionally, this gives evidence for a subsurface layer enriched in ice and volatiles.”
Data relevant to the possibility of subsurface ice is also emerging from Dawn’s Gamma Ray and Neutron Detector (GRaND), which began acquiring its primary data set in December. Neutrons and gamma rays produced by cosmic ray interactions with surface materials provide a fingerprint of Ceres’ chemical makeup. The measurements are sensitive to elemental composition of the topmost yard (meter) of the regolith.
This map shows a portion of the northern hemisphere of Ceres with neutron counting data acquired by the gamma ray and neutron detector (GRaND) instrument aboard NASA’s Dawn spacecraft. Credits: NASA/JPL-Caltech/UCLA/ASI/INAF
In Dawn’s lowest-altitude orbit, the instrument has detected fewer neutrons near the poles of Ceres than at the equator, which indicates increased hydrogen concentration at high latitudes. As hydrogen is a principal constituent of water, water ice could be present close to the surface in polar regions. But the subsurface does not have the same composition all over Ceres, according to data from the visible and infrared mapping spectrometer (VIR), a device that looks at how various wavelengths of sunlight are reflected by the surface, allowing scientists to identify minerals.
This colorized global map of Ceres was created from a clear-filter mosaic. Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Haulani Crater in particular is an intriguing example of how diverse Ceres is in terms of its surface material composition. This irregularly-shaped crater, with its striking bright streaks of material, shows a different proportion of surface materials than its surroundings when viewed with the VIR instrument. While the surface of Ceres is mostly made of a mixture of materials containing carbonates and phyllosilicates, their relative proportion varies across the surface.
Dawn scientists also reported in an LPSC scientific session that the VIR instrument has detected water at Oxo Crater, a young, 6-mile-wide feature in Ceres’ northern hemisphere. This water could be bound up in minerals or, alternatively, it could take the form of ice. This water-bearing material could have been exposed during a landslide or an impact – perhaps even a combination of the two events. Dawn will continue to observe this area.
http://www.nasa.gov/feature/jpl/bright-spots-and-color-differences-revealed-on-ceres
Recent Comments