Oblique view of Ceres’s bright spots

Occator Crater on Ceres

Cool image time! The image above is a newly released image of Occator Crater on Ceres, the location of the dwarf planet’s double bright spots, taken by Dawn in October.

I have cropped the image to focus on the crater and the bright spots. Unlike most previous images, this one is taken from an angle to bring out the topography, which also confirms what other data had shown, that the bright spots are not on top of any peaks. If anything, they appear to be located at low spots in the crater, as that previous data had suggested.

Though the spots are not really very bright, they are very bright relative to the dark surface of Ceres. This is why it is difficult to get a good image of them. Either you have to over-expose the spots to see the surface details around them, or under-expose the surface around them to see some detail in the spots. This image tries to find a middle ground.

Eventually they will move Dawn in very close to try to get higher resolution images of the spots alone. At that time we might finally be able to get a better understanding of what causes them.

The first Ceres atlas

Ceres's first atlas

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.

Dawn’s first close look at Ceres’s poles

Ceres's poles

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.

Dawn begins descent to final orbit around Ceres

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.

Closing in on Ceres’s bright spots

Ceres's bright spots

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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New sharp images of Ceres from Dawn

The Lonely Mountain on Ceres/>

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.

Haze spotted over Ceres’ double bright spot

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.

Dawn resumes descent to Ceres

After a several week pause while engineers analyzed the issue that caused the spacecraft to go into safe mode on June 30, they have now resumed their descent to a lower orbit to take higher resolution images of Ceres.

The spacecraft experienced a discrepancy in its expected orientation on June 30, triggering a safe mode. Engineers traced this anomaly to the mechanical gimbal system that swivels ion engine #3 to help control the spacecraft’s orientation during ion-thrusting. Dawn has three ion engines and uses only one at a time. Dawn’s engineering team switched to ion engine #2, which is mounted on a different gimbal, and conducted tests with it from July 14 to 16. They have confirmed that the spacecraft is ready to continue with the exploration of Ceres.

Ceres’ white spots might be salt not water

The uncertainty of science: The principal investigator of Dawn has indicated that the preliminary data they have gotten of Ceres’ white spots strongly suggests that they are not water but salt.

The mystery is far from completely solved, Russell cautioned. The team failed to get the quality of measurements they wanted in examining the spots, and they’ll have to try again at a closer orbit — like the next planned mapping orbit, which will take them from 2,700 miles over the surface to just 900. The photos taken at that height will also have significantly better resolution, which should further help the team determine what the spots are made of.

But based on the spectral data the team did get, Russell said, the spots “really don’t look like mounds of ice. … The bright spots are probably — like you might find in the desert on Earth — a salt plain where maybe water came out at one time and evaporated,” Russell said.

None of this is confirmed, and won’t be until they lower Dawn’s orbit to get higher resolution images. However, this must wait because they have extended Dawn’s mapping orbit for now as they review the issue that caused the safe mode incident on June 30.

Dawn recovers from safe mode

Spot 1

Beginning on June 30 Dawn experienced an as yet unexplained “anomaly” that put it into safe mode for several days.

According to JPL, engineers have uploaded “configuration changes” that solved the problem, and the spacecraft has returned to normal operations, continuing its second mapping orbit of Ceres. From this position they are gathering wide angle images of the entire planet, from which they will construct a detailed global map to be used as a baseline during later more detailed close-up orbits. For example, they released this very nice image today of what is called “Spot 1”, shown on the right. I have cropped it to focus on the spot itself. Looks almost like scattered snow on the surface, doesn’t it?

Another Dawn image of some of Ceres’ bright spots

The double bright spot, not over-exposed

Cool image time! As part JPL’s regular release of images from Dawn, one image of Ceres’ bright double spots was purposely not over-exposed. Thus, the surface is almost black (as it really looks), while the small cluster of spots stands out brightly but with some additional detail. (If you download the full image and use a graphics program to brighten it you will see that this is the double bright spot located inside a large crater.)

I have cropped and enlarged the original image to focus on the double spot. As you can see the brightest spot has a mottled look, almost like we are looking down at a snow-capped peak.

Though the leading theory remains that this is ice, this theory has not been confirmed yet. Make no assumptions or you may discover you are wrong.

A closer close-up of Ceres’ double bright spot

Closer look at Ceres' double bright spot

Cool image time! In a new press release, the Dawn science team has unveiled a new close-up of Ceres’ double bright spot, shown on the right.

At least eight spots can be seen next to the largest bright area, which scientists think is approximately 6 miles (9 kilometers) wide. A highly reflective material is responsible for these spots — ice and salt are leading possibilities, but scientists are considering other options, too.

In other words, they still have not confirmed through spectroscopy, that these bright spots are ice.

Note also that they have reduced the image’s brightness so that the bright spots do not over expose as much as in past images. This not only allows more details to come out, but it portrays Ceres’ very dark surface more accurately. Even so, the image still shows that surface as brighter than it actually is.

A mountain on Ceres

The press release also described a second image, showing a single lonely mountain on the planet’s horizon, rising up three miles from the planet’s surface, shown in the cropped image to the left. Overall this image, as well as the others, suggest that the surface of Ceres is generally far less rough than we should expect.

Another science mystery to unravel!

New close-up image of Ceres’s double bright spots

close-up of Ceres's bright spots

Cool image time! The Dawn science team has released a some new close-up images of Ceres, including a much higher resolution image of the dwarf planet’s double bright spot, which now resolves itself into a cluster of two larger spots with a half dozen smaller spots scattered nearby.

The region with the brightest spots is in a crater about 55 miles (90 kilometers) across. The spots consist of many individual bright points of differing sizes, with a central cluster. So far, scientists have found no obvious explanation for their observed locations or brightness levels.

“The bright spots in this configuration make Ceres unique from anything we’ve seen before in the solar system. The science team is working to understand their source. Reflection from ice is the leading candidate in my mind, but the team continues to consider alternate possibilities, such as salt. With closer views from the new orbit and multiple view angles, we soon will be better able to determine the nature of this enigmatic phenomenon,” said Chris Russell, principal investigator for the Dawn mission based at the University of California, Los Angeles.

To my eye, these bright areas resemble a wide flat caldera of a volcano. Instead of being at the top of a peak, the caldera is like a lava pool, almost like a large lake. In this case, the large spots are lakes of frozen ice that periodically melt and flow. The smaller spots are likely smaller vents where water can bubble up from below during active periods. When not active, the water will be frozen. Since ice is white and Ceres is very dark, the pools and vents appear extremely bright in these images.

I am speculating however. We will have to wait for much better images to know for sure.

Dawn makes a movie of Ceres

Cool image time! Using images that Dawn has accumulated since it entered orbit around Ceres, scientists have created an animation showing the dwarf planet as it rotates.

Video below the fold. Note that this is an animation. They have filled in the gaps between images to make the rotation smooth, exaggerated the scale two times to bring out details, and added a background of stars that is not visible in the original images. Even so, this video is scientifically useful, as it shows Ceres in its entirety. It is also very spectacular.
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It looks like the Moon!

craters on Ceres

Cool image time! Dawn has now swooped down to 3,200 miles, and provided a very nice image of the cratered surface of Ceres. Though it does appear to resemble the Moon, there are some differences that come to mind if you take a close look at the full resolution image. The surface appears smoother. All of the craters appear worn or eroded or less rugged. Also, there are no mountains. The terrain resembles the Moon’s lowlands or maria, but more so.

Note that the region in this picture is tantalizingly close to the double bright spot, but does not include it. Because Dawn is still easing its way into its first survey orbit of 2,700 miles elevation, it only takes pictures when it stops firing its ion engine, which it is doing almost all the time to get where it wants to be. Thus, they apparently only had time for this image.

The spacecraft enters its mapping orbit on June 3. Expect some cool images, including the first good images of the double bright spots, shortly thereafter.

New images of Dawn’s double bright spot

The double spot on Ceres

Cool image time! Dawn has released a new animation made from images taken in early May, showing more details of the dwarf planet’s double bright spot.

As they note at the link, the double spot is now “revealed to be composed of many smaller spots.” As they also add, “Their exact nature remains unknown.”

Dawn’s engineers are now beginning to ease the spacecraft down to its survey orbit, about 2,700 miles above the surface.

Dawn’s chief engineer gives us a detailed update

Link here. Chief engineer Marc Rayman loves to write about Dawn, and his posts on the Dawn blog are probably the most information-packed of any spacecraft blog I have ever read. Key quote this time:

Dawn’s extensive photographic coverage of the sunlit terrain in early May will include these bright spots. They will not be in view, however, when Dawn spies the thin crescent of Ceres in its next optical navigation session, scheduled for April 10.

The orientation of the spacecraft and asteroid now are such that there is no point taking pictures, as most of the asteroid is in darkness.

Read it all, however. He gives a masterful overview of what is going to happen in the coming months.

Water ice volcanoes on Ceres

Data collected by Dawn since it entered orbit around Ceres on March 6 now strongly suggests that the bright spots on the surface are produced by venting water,

Andreas Nathues, principal investigator for Dawn’s framing camera, says the feature has spectral characteristics that are consistent with ice. Intriguingly, the brightness can be seen even when the spacecraft is looking on edge at the crater rim, suggesting that the feature may be outgassing water vapor above the rim and into space. “Ceres seems to be indeed active,” he says. The feature brightens through the course of the day, and then shuts down at night. Nathues says the behavior is similar to that of comets.

More here. By mid-April Dawn should finally settle this with high resolution images.

Dawn bears down on Ceres

Ceres' cratered surface

More cool images! As Dawn moves in on Ceres and prepares to enter orbit on March 6, it has managed to assemble enough images to produce a global map of the almost spheroid-shaped giant asteroid.

The bright spots however remain a mystery which cannot be answered until we get higher resolution images from much closer. Hopefully, Dawn will be able to do this once it is in orbit.

The brightest spot on Ceres has a partner

Ceres' double bright spots

Cool images! Dawn’s newest images have revealed that the brightest spot on Ceres, shown on the right in a cropped version of the full image, has a dimmer companion.

“Ceres’ bright spot can now be seen to have a companion of lesser brightness, but apparently in the same basin. 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,” said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles.

The spots are still too small for Dawn’s camera to resolve. That they are inside what looks like a crater is very puzzling. If they are water-ice, why are they so bright and distinct? One one think the ice would pile up along the crater wall, but then, that’s what we think based on our experience here on Earth with wind, rain, and our heavy gravity. Ceres is cold, has no atmosphere, and a tiny gravitational field. Every geological process will proceed in a different manner.

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