Tag: asteroids

Link here. Though the story initially focuses on the possibility that the mission might be extended a few extra months until the spacecraft’s fuel runs out, it also gives a good summary of what has been learned so far about the dwarf planet, including the theory that Ceres was once an “ocean world.”

[Carol Raymond, Dawn’s deputy principal investigator,] said Ceres appears to be a former ocean world and could have once been similar to Europa or Enceladus, the icy moons of Jupiter and Saturn. “One of the things that we anticipated about Ceres before getting there is that it’s a former ocean world,” Raymond said. “We’re so interested in going to Europa and Enceladus, and these other interesting objects in the outer solar system because we think they harbor subsurface oceans at present, and possible habitable environments, and possibly even locations where there’s extant life.

“Ceres appears to have been one of those objects in the past, when it was younger and hotter,” Raymond said. “What we’re looking at now is, we believe, the remnant of a frozen ocean. The salt is left over from the brines that were concentrated as the ocean froze out, so it’s all a fairly consistent story that Ceres is a former ocean (world) where the ocean froze, and now we’re interrogating the chemistry, essentially, of that ocean-rock interface through the subsurface layers that we’re detecting on Ceres.”

The data has found the high latitudes to have lots of hydrogen, suggesting water-ice on or near the surface. The bright salt patches also suggest frozen water below the surface that left behind the salt when it reached the surface and evaporated away.

Cool image time! As Dawn continues its survey of Ceres the science team is beginning to release images looking sideways at the planet, rather than straight down, in order to get a better understanding of the topography. The image to the right is an example. It shows the area around 37-mile-wide Fluusa Crater. I have cropped it to emphasize the most rugged areas, especially the jagged cliff meandering away towards the horizon.

This image provides a hint at the differences between Ceres and the Moon. Up until now Dawn images have given the impression that Ceres is very much like the heavily cratered lunar surface. The terrain in this image however suggests to me that Ceres’ surface crust is much less dense because of the low gravity, and thus has a light puffy feel to it. The Moon’s surface is rarely this uneven, as its higher gravity has pounded things down, smoothing them out somewhat.

Cool image time! As Dawn continues its close survey of Ceres, the science team has released this image of Dantu Crater, showing the bright spots on its rim as well as fractures on the crater floor. The picture was taken in December and has a resolution of about 120 feet per pixel.

Though scientists now favor salt deposits of some kind as the cause of the bright areas on Ceres, they also recognize that this theory is not yet proven. Moreover, the theory suggests that the salt was deposited as part of a water brine. When the water in the brine evaporated away, it left the salt behind. The problem, however, is that we do not yet have direct evidence that there is any water on Ceres at all, either on the surface or in the interior, which makes this theory exceedingly uncertain.

The Dawn science team today released a set of close-up images of several craters on Ceres, showing a number of geological features similar but different than features seen in lunar craters.

The image on the right, of Kupalo Crater, shows the same kind of bright material on the rim that is seen on the floor of Occator Crater as two bright areas. The bright material is now believed to be a salt deposit leeched from beneath the surface. Other craters showed extensive fractures in their floor as well as lobes and scarps.

The Dawn science team has now released new high resolution images of Ceres taken from the spacecraft’s lowest orbit.

Dawn took these images of the southern hemisphere of Ceres on Dec. 10, at an approximate altitude of 240 miles (385 kilometers), which is its lowest-ever orbital altitude. Dawn will remain at this altitude for the rest of its mission, and indefinitely afterward. The resolution of the new images is about 120 feet (35 meters) per pixel.

Among the striking views is a chain of craters called Gerber Catena, located just west of the large crater Urvara. Troughs are common on larger planetary bodies, caused by contraction, impact stresses and the loading of the crust by large mountains — Olympus Mons on Mars is one example. The fracturing found all across Ceres’ surface indicates that similar processes may have occurred there, despite its smaller size (the average diameter of Ceres is 584 miles, or 940 kilometers). Many of the troughs and grooves on Ceres were likely formed as a result of impacts, but some appear to be tectonic, reflecting internal stresses that broke the crust.

Make sure to click on the link. The images show that Ceres is not the dull boring surface that the wider shots have suggested.

Using data during Dawn’s first orbit of Ceres German scientists have compiled a global atlas of the dwarf planet.

The images used for this are the wide angle survey images, which won’t show the smallest objects because they were taken from about 2,700 miles above the surface. Nonetheless, this atlas gives scientists a baseline for studying the giant asteroid.

The Dawn science team have released their first images of the north and south poles of Ceres.

The region around the south pole appears black in this view because this area has been in shade ever since Dawn’s arrival on March 6, 2015, and is therefore not visible. At the north polar region, craters Jarovit, Ghanan and Asari are visible, as well as the mountain Ysolo Mons. Near the south pole, craters Attis and Zadeni can be seen.