Scientists are now getting their closest-ever views of Ceres, thanks to NASA’s Dawn spacecraft, which is now in its lowest orbit around the dwarf planet. As posted by NASA on July 2, 2018, the new images being sent back are fantastic – high-resolution views of the rugged surface and in particular, the famous “bright spots” in Occator Crater and elsewhere. These spots, which stand out starkly against the darker background surface, have intrigued scientists and the public alike ever since they were first discovered by Dawn when it arrived at Ceres in 2015.
Dawn reached its final, lowest orbit on June 6, and has been busy sending back thousands of images and other data about Ceres. This will help scientists to understand how Ceres formed and evolved over time, and how it appears to still be geologically active today, despite being so small compared to other planets.
The newest images from Ceres have a resolution of less than 5 metres per pixel. As Dr. Andreas Nathues, Framing Camera Lead Investigator, said:
“The data exceeds all our expectations.”
The bright spots, now known to be composed of sodium carbonate, are one of the biggest clues as to current activity, and the new images and data will help to finally answer the question of how they got there. Dawn has now taken the closest-ever images of Cerealia Facula, the largest deposit in the center of Occator Crater, after firing its ion engine last week to adjust its orbit trajectory. According to Dawn’s chief engineer and project manager, Marc Rayman, of NASA’s Jet Propulsion Laboratory, Pasadena, California:
“Acquiring these spectacular pictures has been one of the greatest challenges in Dawn’s extraordinary extraterrestrial expedition, and the results are better than we had ever hoped. Dawn is like a master artist, adding rich details to the otherworldly beauty in its intimate portrait of Ceres.”
Dawn’s new orbit now takes it to a distance of only 35 kilometres (22 miles) above Ceres’ surface. Previously, the lowest orbit was 385 kilometres (240 miles), so this is a big improvement for being able to see more details on the surface, including in the spots.
The spots, evaporate deposits composed of sodium carbonate, are thought to be left over from when water came up to the surface from deeper below and then evaporated in the extremely tenuous and sporadic water vapour “atmosphere.” That water could be either from a shallow sub-surface reservoir or from a deeper reservoir of salty brines percolating upward through fractures. The deposits in Occator Crater are the largest and brightest of these deposits. As with many discoveries in planetary science, they were completely unexpected, and show that Ceres is not just an inert ball of rock and ice. As noted by Carol Raymond, the Dawn mission’s principal investigator:
“The first views of Ceres obtained by Dawn beckoned us with a single, blinding bright spot. Unraveling the nature and history of this fascinating dwarf planet during the course of Dawn’s extended stay at Ceres has been thrilling, and it is especially fitting that Dawn’s last act will provide rich new data sets to test those theories.”
Ceres is also considered to be an asteroid, and is the largest object in the main asteroid belt between Mars and Jupiter. As well as the carbonate deposits, Dawn also found other unusual features, such as Ahuna Mons, a conical mountain which sits in isolation on Ceres’ surface, with nothing else like it nearby. It is approximately 5 kilometres (3 miles) tall and its formation is thought to involve cryovolcanism (an icy form of volcanism).
Ceres is a bizarre world, the largest in the main asteroid belt, with bright carbonate deposits splattered on its surface, a weird isolated conical mountain, landslides and a possible subsurface layer of water. NASA’s Dawn spacecraft has now taken the highest-resolution images of Ceres, showing us how just unique this dwarf planet really is.
This article was first published on EarthSky.