“Ceres continues to amaze, yet puzzle us, as we examine our multitude of images, spectra, and now energetic particle bursts,” said Chris Russell from the University of California in Los Angeles.
A new color-coded topographic map shows more than a dozen recently approved names for features on Ceres, all eponymous for agricultural spirits, deities, and festivals from cultures around the world. These include Jaja, after the Abkhazian harvest goddess, and Ernutet, after the cobra-headed Egyptian harvest goddess. A 12-mile (20-kilometer) diameter mountain near Ceres’ north pole is now called Ysolo Mons, for an Albanian festival that marks the first day of the eggplant harvest.
Another new Ceres map, in false color, enhances compositional differences present on the surface. The variations are more subtle than on Vesta, Dawn’s previous port of call. Color-coded topographic images of Occator (oh-KAH-tor) crater, home of Ceres’ brightest spots, and a puzzling cone-shaped 6-mile-high (4km) mountain are also available. Scientists are still trying to identify processes that could produce these and other unique Cerean phenomena.
“The irregular shapes of craters on Ceres are especially interesting, resembling craters we see on Saturn’s icy moon Rhea,” said Carol Raymond from NASA’s Jet Propulsion Laboratory in Pasadena, California. “They are very different from the bowl-shaped craters on Vesta.”
A surprising bonus observation came from Dawn’s gamma ray and neutron spectrometer. The instrument detected three bursts of energetic electrons that may result from the interaction between Ceres and radiation from the Sun. The observation isn’t yet fully understood but may be important in forming a complete picture of Ceres.
“This is a very unexpected observation for which we are now testing hypotheses,” Russell said.
Dawn is currently orbiting Ceres at an altitude of 915 miles (1,470km), and the spacecraft will image the entire surface of the dwarf planet up to six times in this phase of the mission. Each imaging cycle takes 11 days.
Starting in October and continuing into December, Dawn will descend to its lowest and final orbit, an altitude of 230 miles (375km). The spacecraft will continue imaging Ceres and taking other data at higher resolutions than ever before at this last orbit. It will remain operational at least through mid-2016.
Dawn made history as the first mission to reach a dwarf planet and the first to orbit two distinct extraterrestrial targets, when it arrived at Ceres on March 6, 2015. It conducted extensive observations of Vesta in 2011 and 2012.