Tag: asteroids

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.

Engineers have fired up Dawn’s ion engine and have begun lowering the spacecraft’s orbit downward.

The spacecraft is now on its way to the final orbit of the mission, called the low-altitude mapping orbit. Dawn will spend more than seven weeks descending to this vantage point, which will be less than 235 miles (380 kilometers) from the surface of Ceres. In mid-December, Dawn will begin taking observations from this orbit, including images at a resolution of 120 feet (35 meters) per pixel.

They’ve also released a nice mosaic showing the double bright spots in Occator Crater as well as the surrounding terrain.

The Dawn science team has released several new false color maps of Ceres, showing the dwarf planet’s topographic and compositional differences.

They have also assigned names to many of the features that Dawn has discovered, including Ysolo Mons for that large peak near the north pole.

Cool image time! The Dawn science team has released a new close-up of Ceres’s Double Bright Spot.

The new up-close view of Occator crater from Dawn’s current vantage point reveals better-defined shapes of the brightest, central spot and features on the crater floor. Because these spots are so much brighter than the rest of Ceres’ surface, the Dawn team combined two different images into a single composite view — one properly exposed for the bright spots, and one for the surrounding surface.

They have also released a detailed topographic map of the crater as well as a fly-around video, which I have posted below the fold. The interesting take-away from this new data is that, while the bright spots look at first glance remarkably like the snow-cap on a mountain-top, they are actually at the low spots in the crater. This suggests that they are instead material that has either bubbled up from below, or flowed downward to the crater bottom.

Be sure you click on the link and look at the full resolution image.
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Cool image time! The Dawn science team has released new images of Ceres, including one of a single mountain they have dubbed the Lonely Mountain.

The mountain, located in the southern hemisphere, stands 4 miles (6 kilometers) high. Its perimeter is sharply defined, with almost no accumulated debris at the base of the brightly streaked slope with bright streaks. The image was taken on August 19, 2015. The resolution of the image is 450 feet (140 meters) per pixel.

I have cropped the image and posted it on the right. Be sure to look at the full resolution version. Not only does the mountain have no debris at its base, it truly is lonely. There are no similar features anywhere near it. It almost looks like someone took a shovel of material out of the ground to create the crater immediately to the south and then dumped that material to create the mountain.

Note that the mountain is more like a mesa, with a flat top, which suggests it is the remains of a higher elevation surface that eroded away in the distant past. The geological processes that could have done this however remain quite puzzling at this point.

Dawn, in orbit around Ceres, has detected a haze above the dwarf planet’s double bright spot, suggesting that the tiny asteroid/planet is still geologically active.

Haze on Ceres would be the first ever observed directly in the asteroid belt. In 2014, researchers using the European Space Agency’s Herschel Space Observatory reported seeing water vapour spraying off Ceres, which suggested that it was geologically active1. At least one-quarter of Ceres’s mass is water, a much greater proportion than seen in most asteroids.

Bright spots pepper Ceres’s surface, but the haze has so far been seen in only one location — a crater named Occator, which has a large bright area at its centre and several smaller spots nearby. Mission scientists have been trying to work out whether the bright spots are made of ice, evaporated salts or other minerals, or something else entirely.

Some team members had been leaning towards the salt explanation, but the discovery of haze suggests the presence of sublimating ice. “At noontime, if you look at a glancing angle, you can see what seems to be haze,” Russell says. “It comes back in a regular pattern.” The haze covers about half of the crater and stops at the rim.