Insulating crust kept cryomagma liquid for millions of years on nearby dwarf planet

February 12, 2019, University of Texas at Austin
The bright spots of Occator Crater shine from the surface of Ceres. Research led by The University of Texas at Austin is helping reveal how the spots formed from cryomagma. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

A recent NASA mission to the dwarf planet Ceres found brilliant, white spots of salts on its surface. New research led by The University of Texas at Austin in partnership with NASA's Jet Propulsion Laboratory (JPL) delved into the factors that influenced the volcanic activity that formed the distinctive spots and that could play a key role in mixing the ingredients for life on other worlds.

The volcanoes on Ceres are cryovolcanoes, a type of volcano that forms on with icy shells and that moves salty water known as cryomagma from underground reservoirs to the surface. Scientists think that cryovolcanoes on Jupiter's icy moon Europa could help foster chemical mixing that could make complex molecules needed for life. Learning more about how these volcanoes work on Ceres—which is a simpler geological environment than Europa—could help scientists get a handle on the primary forces that drive their activity.

"Cryovolcanism looks to be a really important system as we look for life," said lead author Marc Hesse, an associate professor at the UT Jackson School of Geosciences. "So we're trying to understand these ice shells and how they behave."

The final version of the research was published online on Feb.8 in the journal Geophysical Research Letters. The research was co-authored by Julie Castillo-Rogez, a planetary scientist at NASA's JPL.

At 585 miles across, Ceres is the largest planetary body in the asteroid belt between Mars and Jupiter. Forged billions of years ago from rock and ice and far enough from the influence of other planets, scientists had thought that Ceres' days of active geology had come to close. But the NASA Dawn mission changed that view when the space probe sent back pictures of bright, white spots at the bottom of impact craters. The spots turned out to be the remnants of cryomagma.

The location of the spots at or near the center of crater basins suggests that the heat and energy generated by asteroid impacts could jumpstart geology on Ceres, creating reservoirs of cryomagma that were then brought to the surface by conduits such as fractures.

The new research looked specifically at the deposits on the floor of the 90-mile-wide crater Occator, which was formed about 20 million years ago. However, the deposits here are as young as 4 million years old, indicating a relatively recent formation geologically speaking with respect to the crater itself. Earlier research conducted by other scientists found that the conditions on Ceres wouldn't allow for the cryomagma generated by the Occator impact to exist for more than about 400,000 years.

Occator Crater on Ceres, with its central bright area called Cerealia Facula. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

The age discrepancy between salt deposits and impact timing raises a question: How could a reservoir of melt stay in a liquid state for millions of years after impact on an otherwise geologically stagnant world?

In their new paper, Hesse and Castillo-Rogez were able to significantly extend the life of the cryomagma by including more up-to-date details on Ceres' crustal chemistry and physics.

"It's difficult to maintain liquid so close to the surface," said Castillo-Rogez. "But our new model includes materials inside the crust that tend to act as insulators consistent with the results from the Dawn observations."

The new calculations indicate that the cryomagma of Occator could last up to 10 million years—a value that doesn't close the time gap completely, but that indicates that the additional data helps make a more realistic cooling timeline.

"Now that we're accounting for all these negative feedbacks on cooling—the fact that you release latent heat, the fact that as you warm up the crust it becomes less conductive—you can begin to argue that if the ages are just off by a few million years you might get it," Hesse said.

Jennifer Scully, a planetary geologist at NASA's JPL who studies Ceres but was not involved with the study, said that the findings are a great contribution toward unpacking the geologic history of an alien world.

"They used more up-to-date data to create their model," said Scully. "This will help in the future to see if all of the material involved in the observed deposits can be explained by the impact, or does this require a connection to a deeper source of material. It's a great step in the right direction of answering that question."

Explore further: Dawn mission to gather more data in home stretch

More information: M. A. Hesse et al, Thermal Evolution of the Impact-Induced Cryomagma Chamber Beneath Occator Crater on Ceres, Geophysical Research Letters (2018). DOI: 10.1029/2018GL080327

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Osiris1
1 / 5 (2) Feb 13, 2019
All that stuff on Ceres was hinted at before Dawn was even concieved of. The sole reason for Dawn was to see just who was there. Only way to do that was to sneak up on it out of the dark of space by using electric propulsion which gave us the ability to 'sneak up'. The propulsion jet cannot beeven seen over a hslf mile away, it is THAT dim.
Early fotos showed thin streaks that looked like streets with lights. All 'airbrushed now. Early fotos showed the 'spots' glowing in the dark on the night side of that planet. Ceres was considered a planet in the 1800's.
NO "SALT" glows in the dark. The rules of chemistry demand energy for everything, and light has a cost in energy that it radiates away. No salt would be so constructed as it is of equal and opposite energy potentials. It takes a LOT of energy ot split it, which is why aluminum is not free metal in nature, for instanct.
That is a MINING station, pure and simple. Miners probably told US to GIT and do not return!
rrwillsj
not rated yet Feb 13, 2019
NO "SALT" glows in the dark.

Really osiriswonder?
You're sure now?
Absolutetively Prepositiverous?

Cause a skulking figure hissed at me out of a dark alley as I passed in smoggy dusking.

Whispering "Hey, buddy! I gotcha a good deal on some genuwhine crystals from Ceres. Right here in my pocket!
For a low, low price. Garaunteed yessirree.
to glow in the dark!"

I just waived him/her/it off.
I may have been born at night but it wasn't last night!

Those last two times I was shanghaied taught me to sober up & flee from proximity to wooloons.
"I went to Sea
To see the World.
What did eye see?
The inside of the tin bucket
I was puking my guts into!"

But, those are stories for another day.

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