It may be the largest object in the asteroid belt that sits beyond Mars, but the dwarf planet Ceres has been surprising scientists ever since it was discovered. Now, NASA's Dawn probe has sent back its closest ever look at the surface of Ceres. This picture, one of the first images returned by Dawn in more than a year, show a rough landscape with a relatively smooth surface.
“This rough landscape suggests these features are on top of ancient terrains. These images offer complementary perspective to the images generally obtained by imaging the surface directly beneath the spacecraft. This example shows that Ceres' limb is relatively smooth despite the rough surface, because this large body is rounded by its own gravity.” NASA said.
This picture is one of the first images returned by Dawn in more than a year, as Dawn moves to its lowest-ever and final orbit around Ceres. Dawn captured this view on May 16, 2018 from an altitude of about 270 miles (440 kilometers). The large crater near the horizon is about 22 miles (35 kilometers) in diameter, which is not far from a series of tholi (small mountains) that include Kwanzaa Tholus. The midsize crater in the foreground is located about 75 miles (120 kilometers) from the large crater.
The Dawn spacecraft has returned many limb images of Ceres in the course of its mission. The images were taken as Dawn is maneuvering to its lowest-ever orbit for a close-up examination of the inner solar system's only dwarf planet. In early June, Dawn will reach its new, final orbit above Ceres. Soon after, it will begin collecting images and other science data from an unprecedented vantage point.
This orbit will be less than 30 miles (50 kilometers) above the surface of Ceres - 10 times closer than the spacecraft has ever been. Dawn will collect gamma ray and neutron spectra, which help scientists understand variations in the chemical makeup of Ceres' uppermost layer. That very low orbit also will garner some of Dawn's closest images yet.
This animation shows Ceres as seen by NASA's Dawn spacecraft from its high-altitude mapping orbit at 913 miles (1,470 kilometers) above the surface. The colorful map overlaid at right shows variations in Ceres' gravity field measured by Dawn, and gives scientists hints about the dwarf planet's internal structure. Red colors indicate more positive values, corresponding to a stronger gravitational pull than expected, compared to scientists' pre-Dawn model of Ceres' internal structure; blue colors indicate more negative values, corresponding to a weaker gravitational pull
Dawn was launched in 2007 and has been exploring the two largest bodies in the main asteroid belt, Vesta and Ceres, to uncover new insights into our solar system. It entered Ceres' orbit in March 2015.
“The team is eagerly awaiting the detailed composition and high-resolution imaging from the new, up-close examination,” said Dawn's Principal Investigator Carol Raymond of NASA's Jet Propulsion Laboratory, Pasadena, California. “These new high-resolution data allow us to test theories formulated from the previous data sets and discover new features of this fascinating dwarf planet.”
This view from NASA's Dawn mission shows Ceres' tallest mountain, Ahuna Mons, 2.5 miles (4 kilometers) high and 11 miles (17 kilometers) wide. This is one of the few sites on Ceres at which a significant amount of sodium carbonate has been found, shown in green and red colors in the lower right image.
Previous findings have suggested that water - one of the key ingredients for life - is present across the entire surface of the rocky planetoid. What's more, the distribution of these icy patches suggests the dwarf is still evolving suggesting it may have its own water cycle beneath the surface.
Ceres is of particular interest to scientists because it is the closest dwarf planet to Earth and may play host to the building blocks needed for alien life. NASA’s Dawn probe has been mapping the object since 2015 and, in a new study, experts used images captured by the craft to study chemicals on Ceres' surface.
Mysterious bright spots dotting the surface of the dwarf planet Ceres have baffled scientists since they were first spotted two years ago. NASA’s Dawn spacecraft captured the first images of two distinctly reflective areas in 2015. A simulation of the bright areas of Occator Crater, Cerealia Facula in the center and Vinalia Faculae to the side, is pictured
Specifically it looked at carbonates, compounds that have previously been detected by Dawn, which are thought to be strong indicators of liquid water. Researchers at Italy's Institute of Astrophysics and Space Planetology in Rome used the probe's visible-infrared mapping spectrometer to anaylse the planet. They found that sodium carbonates, salts of carbonic acid, can be found across the entire observed surface of Ceres. The camera reads the chemical spectrum of compounds found far below the planet's exterior to identify them.
Some carbonate patches, which are as long as a kilometre-wide (0.6 miles), featured sodium carbonate in its hydrated form. This could only occur around liquid water, suggesting the dwarf planet has a subsurface ocean. The Italian team, led by Dr Filippo Carrozzo, wrote in their paper:
“Hydrated sodium carbonates could form early in a global ocean in equilibrium with the altered rocky phase and be incorporated in Ceres' crust upon freezing of that ocean.”
The researchers also focussed on patches of ice covering the walls of Ceres's Jugling impact crater (pictured). The crater, found on Ceres's southern hemisphere, is shadowy, dark and unlike other northern hemisphere craters where water ice has previously been found
Some craters showed unique characteristics, such as floor fractures, that the authors say indicate areas where water had been ejected. The researchers also focused on patches of ice covering the walls of Ceres's Jugling impact crater. The crater, found on Ceres's southern hemisphere, is shadowy, dark and unlike other northern hemisphere craters where water ice has previously been found.
To better understand Juling's water ice features, the Italian team analysed light spectrum data previously obtained by the Dawn mission. Specifically, they compared how the amount of ice on the crater's walls has changed over time as the sun shone on different regions.
Their results showed a clear increase of the area covered by the crater's ice-rich wall as time progressed. According to the authors, the trend between ice abundance and solar flux suggests that seasonal cycles of water are responsible for the observed increase. The full findings of the study were published in the journal Science Advances.