Ceres' Mystery Bright Dots May Have Volcanic Origin
As NASA's Dawn mission slowly spirals in on its dwarf planet target, Ceres' alien landscape is becoming sharper by the day.
As NASA's Dawn mission slowly spirals in on its dwarf planet target, Ceres' alien landscape is becoming sharper by the day. And, at a distance of only 29,000 miles (46,000 kilometers), the robotic spacecraft has revealed multiple bright patches on the surface, but one of the brightest spots has revealed a dimmer bright patch right next door.
"Ceres' bright spot can now be seen to have a companion of lesser brightness, but apparently in the same basin," said Chris Russell, of the University of California, Los Angeles (UCLA) and principal investigator for the Dawn mission. "This may be pointing to a volcano-like origin of the spots, but we will have to wait for better resolution before we can make such geologic interpretations."
Regions of higher than average albedo (reflectiveness) have been long known to exist on Ceres, but the low resolution of the observations have prevented planetary scientists from interpreting what they could be. But with the slow arrival of Dawn, these bright spots turn out to be discrete locations that might indicate surface ice features - possibly evidence for cryo-volcanism.
Cryovolcanoes can form on cold bodies in the solar system, such as the moons orbiting Jupiter and Saturn or dwarf planets in the Kuiper belt, but rather than molten rock being ejected to the surface (such is the case for regular volcanoes on Earth), liquid water, methane or ammonia may be forced to the surface after undergoing some heating through radioactive or tidal processes. Once vented, these cryovolcanoes may leave frozen residue on the surface, possibly resembling what we are beginning to see on Ceres. But until we get closer, any positive identification will remain elusive for the time being.
"The brightest spot continues to be too small to resolve with our camera, but despite its size it is brighter than anything else on Ceres," said Andreas Nathues, of the Max Planck Institute for Solar System Research in Gottingen, Germany, and lead investigator for Dawn's framing camera team. "This is truly unexpected and still a mystery to us."
Having already visited massive asteroid Vesta from 2011 to 2012, Dawn is slowly approaching its second asteroid belt target where it will continue to explore for the next 16 months. Soon after, its thruster fuel will run dry and it will remain, stuck in orbit around Ceres as a permanent artificial satellite of the dwarf planet. Before this happens, however, Dawn will transform our view of Ceres, providing us with invaluable and historic knowledge of the solar system's innermost dwarf planet.
These images of dwarf planet Ceres, processed to enhance clarity, were taken on Feb. 19, 2015, from a distance of about 29,000 miles (46,000 kilometers), by NASA's Dawn spacecraft. Dawn observed Ceres completing one full rotation, which lasted about nine hours.
NASA's Dawn spacecraft orbited the massive asteroid Vesta in 2011 and 2012, giving us an unprecedented look at the protoplanet's landscape, craters and mineral composition. The probe, which is now on its way to dwarf planet Ceres, not only revealed the evolution of Vesta, it also provided vital clues as to the evolution of our solar system. Now,in new images published by NASA
, an unusually colorful Vesta landscape is on display. Using data from the mission, scientists at Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany have produced a rather psychedelic view of this otherwise bland landscape. Dawn's camera system is equipped with seven filters, each filter sensitive to a specific wavelength of light. Normally, Vesta would look gray to the naked eye, but when analyzing the ratios of light through Vesta's filters, the landscape pops with color. Shown here, the flow of material inside and outside a crater called Aelia is demonstrated. As different minerals reflect and absorb different wavelengths of light, this composite image is alive with color, each shade representing different kinds of minerals littering Vesta's landscape.
This is Antonia, a crater located inside the huge Rheasilvia basin in the southern hemisphere of Vesta. From this image, planetary scientists have been ableto deduce that
"the light blue material is fine-grain material excavated from the lower crust. The southern edge of the crater was buried by coarser material shortly after the crater formed. The dark blue of the southern crater rim is due to shadowing of the blocky material."
The impact crater Sextilia can be seen in the lower right of this image. The mottled dark patches are likely impact ejecta from a massive impact and the redish regions are thought to be rock that melted during the impact. The diversity of the mineralogy is obvious here. "No artist could paint something like that. Only nature can do this," said Martin Hoffman, a member of the framing camera team at Max Planck Institute.
Earlier images of Vesta have shown an unusual "pitted terrain" on the floors of the craters named Marcia (left) and Cornelia (right). Once again, the varied colors demonstrate the different minerals and processes that cover Vesta's surface.
of Vesta shows the abundance of hydrogen on Vesta's surface. Note that the hydrogen signal is enhanced near the asteroid's equator. The hydrogen is likely from hydroxyl or water bound to minerals in Vesta's surface.
Another, earlier view of Antonia crater, demonstrating the mineral diversity of the region.
This is the distinctive Oppia crater on Vesta, an impact that occurred on a slope. This produced an asymmetric ejecta distribution around the crater -- the red/orange ejecta material is more abundant around the downward slope than around the upward portion.