White spots on Ceres

[Magical Realist]

"NASA's Dawn spacecraft will have plenty of mysteries to investigate when it begins orbiting the dwarf planet Ceres next month, as the probe's latest photos attest.

Dawn's most recent images of Ceres, taken Feb. 12 at a distance of 52,000 miles (83,000 kilometers) away, show an abundance of craters on the dwarf planet, as well as numerous bright spots that have scientists baffled.

"As we slowly approach the stage, our eyes transfixed on Ceres and her planetary dance, we find she has beguiled us but left us none the wiser," Dawn principal investigator Chris Russell of UCLA said in a statement. "We expected to be surprised; we did not expect to be this puzzled."

The new photos, which have a resolution of 4.9 miles (7.8 km) per pixel, are the sharpest ever taken of Ceres, NASA officials said.

A large, flickering white spot was also visible in photos Dawn took of Ceres last month.

"We can confirm that it is something on Ceres that reflects more sunlight, but what that is remains a mystery," Dawn mission director and chief engineer Marc Rayman, of NASA's Jet Propulsion Laboratory in Pasadena, California, told Space.com via email at the time."===http://www.space.com/28579-ceres-bright-...hotos.html

[Image: dawn-white-spots.jpg]

[Image: Ceres-bright-tight.jpg]

[Yazata]

I'm just speculating, but perhaps Ceres is composed mostly of ice, and perhaps meteorite impacts blow away a darkened surface and expose the more pristine material underneath.

[elte]

I was thinking something not too different, like it could have been that a meteorite strike melted some water and it refroze reflectively clean and smooth.

[Yazata]

The latest issue of New Scientist has an interesting article on the white spots.

Several of bits of information:

First, there's evidence that Ceres is outgassing water vapor.

Second, the white spots vary in brightness depending on what hour of the Ceres day it is. They are dimmest in the morning, after sunrise. They get brighter throughout the day, reaching maximum brightness in the Ceres afternoon after a day of the Sun shining on them.

Finally, the spots are raised relative to Ceres surface. When the Dawn spacecraft is tangential to them, looking at them from the side as it were, they appear to be raised even higher than the rim of the crater they are in. They are white mountains.

Putting it together, there seem to be two leading theories.

The first is the giant-comet theory. This has Ceres outgassing water vapor when it's heated by the Sun, much as comets do. Presumably it freezes and falls back as something like snow.

The second is the little-planet theory. This interprets the white lumps as cryo-volcanoes, where water and ice play the role of magma and rock. A planetary scientist at the U. of Arizona has criticized this theory because he doesn't think that there is enough heat deep in Ceres to drive vulcanism. But he also said that it might be most likely in the floors of deep impact craters, where Ceres' icy crust would probably be thinnest. And that's where these white spots are.

My own layman's speculation is that perhaps both these theories are right and what's happening has similarities to both processes.

Of course in real life this is highly speculative. There are still too many variables regarding the condition and composition of Ceres' crust, temperatures at different latitudes and depths, whether there is liquid water beneath the crust, and whatever, to say for sure what's happening. Hopefully the Dawn spacecraft can provide some of that information.

One thing we know for sure is that Ceres is a more interesting place than was perhaps expected.

[stryder]

While I'm interested in the actual real world reasoning of what the light points are, unfortunately my sense of humour has got the better of me. Those spots kind of reminded me of the [wiki]Captain_Scarlet[/wiki] intro with the Mysteron's.

https://www.youtube.com/watch?v=bV8YbLvGrb0

As for what it actually is...
If it's a sunlight reflection off a reflective surface, the reflection does appear to be heading back at the angle the picture was taken, which might not be right direction in relationship to sunlight/shadowing. I wondered if it could be a lander of some description as they would have a solar array on both the base station and any rovers too.

[Yazata]

Here's something frm Nature on the white spots.

http://www.nature.com/news/mystery-of-ce...ws-1.17313

It seems that there are a number of these spots on Ceres and not all of them are alike.

Some (particularly the one known as Spot 1) appear dark in infrared and appear to be ice at the bottom of impact craters.

Others seem to be associated with "icy plumes".

A mystery is that the two brightest spots (the ones in the photo in the OP) that together are known as 'Spot 5' aren't visible on infrared.

[Mr Doodlebug]

Orbs.

[Magical Realist]

"We've been wondering about those bright, white spots on the dwarf planet Ceres ever since the Dawn spacecraft arrived there in March. Speculation was all over the map: many people's gut reaction said water ice, others fantasized about ice volcanoes (or Death Stars). With each passing month (and subsequent image release), the answer seemed to be some sort of salt. But scientists working with the spacecraft's measurements have remained relatively tight-lipped on the subject, waiting for Dawn to inch closer and closer to the surface of Ceres before making a call.

Today, two different papers were published in the journal Nature. One, led by Andreas Nathues from the Max Planck Institute for Solar System Research, claims that the bright areas (of which there are more than 100) contain a magnesium sulfate called hexahydrite. Over time, asteroids impacted Ceres' surface and exposed a subsurface layer made of briny water-ice, Nathues' team claims. The hexahydrite, a salty substance that's of the same ilk as Epsom salt, is just the residue that remains after the exposed water-ice evaporates."===http://www.theverge.com/2015/12/9/988066...-dawn-nasa

[Image: EPSOM-SALTS.jpg]

[Image: alien_in_bubble_bath_poster-r6b0d11b2ec8...vr_324.jpg]

[C C]

The hexahydrite, a salty substance that's of the same ilk as Epsom salt, is just the residue that remains after the exposed water-ice evaporates."

Would have been great for the sore feet of asteroid miners as envisioned 50 years ago, before nanolect microbots emerged on the horizon to harvest it as a resource. But maybe Ceres could still be set aside to serve as a retro-tech reservation for Ludds and other antiquated human remnants that resisted transapient upgrade.

[Yazata]

Here's some extreme close-up photos of the white spots. As the Dawn spacecraft runs out of maneuvering fuel they are being crazier with how they steer it closer and closer to Ceres. (If it's going to die soon anyway, it's no big loss if they crash it now.) It's skimming only about 20 miles above Ceres at the closest approach in its orbit. Its cameras can get good resolution.

http://earthsky.org/space/stunning-new-v...ight-spots

https://www.space.com/41061-dawn-spacecr...hotos.html

https://dawn.jpl.nasa.gov/multimedia/images/ceres.html

https://www.jpl.nasa.gov/blog/columns/dawn-journal/

They do seem to be raised and appear to be made out of salts, as MR reported earlier. Still unclear exactly how the salts got there.