What's up with Ceres' mysterious bright spots? Reply hazy, ask again later

July 24, 2015 by Alan Boyle, Universe Today
The brightest spots on Ceres are seen in this image taken by NASA’s Dawn spacecraft on June 6, 2015. The picture was taken from an altitude of 2,700 miles (4,400 kilometers). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

The crater that contains those puzzlingly bright spots on Ceres may harbor an equally puzzling haze. Or not. The hints of haze on the dwarf planet, seen in some of the images coming from NASA's Dawn spacecraft, add another intriguing twist to Ceres' mysteries.

The hubbub over haze arose this week during the Exploration Science Forum at NASA's Ames Research Center in California. For months, Dawn's scientists have been observing – and trying to make sense out of – unusually reflective spots within Ceres' craters that show up when the asteroid turns into the sunlight. The team has speculated that they could be frozen pools of water ice, or patches of light-colored, salt-rich material.

The brightest spots are known collectively as Spot 5, and sit inside Occator Crater on Ceres. Dawn's principal investigator, Chris Russell of the University of California at Los Angeles, told the forum that some type of haze could be seen inside the crater at certain times of Ceres' day, according to reports from Nature and the Planetary Society. Nature quoted Russell as saying the bright spots "could be providing some atmosphere in this particular region of Ceres."

Last year, scientists with the European Space Agency's Herschel mission reported detecting signs of rising from Ceres' surface, and it would be tempting to suggest that the water vapor is emanating from bright icy spots and creating the haze. That would strengthen Ceres' status as the only asteroid with a significant atmosphere and a subsurface reservoir of water, and stoke speculation about life on Ceres.

However, Russell told Universe Today that it's way too early to give in to temptation.

"I was speaking from less than a handful of images, and the interpretation of the images is disputed by some team members," Russell said in an email. "I would like the debate to go on internally before we make a pronouncement one way or the other. I of course have my personal opinion, but I am not always right."

Russell said the ice-vs.-salt debate is continuing. "I originally was an advocate of ice, because of how bright the spots seemed to be," he said. However, the bright material's albedo, or reflectivity factor, is about 50 percent – which is less than Russell originally thought. "This could be salt and is unlikely to be ice. I think the team opinion is now more in line with salt," he said.

Either way, Russell doesn't see any way for the spots to form without internal activity on Ceres. "Thus, the very existence of the spots tells us that there is some active process going on," he told Universe Today.

Will we ever know if the haze is for real? Or what the spots are made of? As the Magic 8-Ball might say, "Ask again later." The Dawn spacecraft recently recovered from a mechanical glitch and is gradually descending to a closer mapping orbit, around an altitude of 900 miles (1,500 kilometers). That will provide a much better look at Occator Crater and what lies within.

"Eventually I am expecting the spectral data will unambiguously tell us what has happened to the surface," Russell said, "but it is a little too soon to be sure."

Explore further: Dwarf planet Ceres offers big surprises for scientists

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5 comments

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docile
Jul 24, 2015
This comment has been removed by a moderator.
baudrunner
not rated yet Jul 24, 2015
Ice might be crystallizing on the surface prior to dematerialization when exposed to sunlight, and the crystalline structures may be acting as a meta-material, scattering the light away.
cracker_mon
not rated yet Jul 25, 2015
It is not so difficult to believe that the reflective matter is a mineral that we on earth have never come across before and that is completely unknown to us. If so we will not know it's properties for many years, if ever. Nothing states that every compound that exists in the universe also has to exist on the Earth, does it?
Billy_Madison
not rated yet Jul 27, 2015
The reflection is in the direct center of a crater, maybe it was the result of a comet collision or some other mass? This just appears as a crime scene from some collision between Ceres and a body made of reflective, icy material.
Tuxford
1 / 5 (3) Jul 28, 2015
Apart from the air pollution, what seem particularly difficult to explain is the relative abundance of so many relatively straight and steep crater walls.

And now NASA is giving us a few more hints, in case further denial becomes impossible? Or just a ploy for money? Or both?

http://www.huffin...d1a4f97?

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