Dawn finds possible ancient ocean remnants at Ceres

Ceres. Credit: NASA/Jet Propulsion Laboratory

Minerals containing water are widespread on Ceres, suggesting the dwarf planet may have had a global ocean in the past. What became of that ocean? Could Ceres still have liquid today? Two new studies from NASA's Dawn mission shed light on these questions.

The Dawn team found that Ceres' crust is a mixture of ice, salts and hydrated materials that were subjected to past and possibly recent geologic activity, and that this crust represents most of that ancient . The second study builds off the first and suggests there is a softer, easily deformable layer beneath Ceres' rigid surface crust, which could be the signature of residual liquid left over from the ocean, too.

"More and more, we are learning that Ceres is a complex, dynamic world that may have hosted a lot of liquid water in the past, and may still have some underground," said Julie Castillo-Rogez, Dawn project scientist and co-author of the studies, based at NASA's Jet Propulsion Laboratory, Pasadena, California.

What's inside Ceres? Gravity will tell.

Landing on Ceres to investigate its interior would be technically challenging and would risk contaminating the . Instead, scientists use Dawn's observations in orbit to measure Ceres' gravity, in order to estimate its composition and interior structure.

The first of the two studies, led by Anton Ermakov, a postdoctoral researcher at JPL, used shape and gravity data measurements from the Dawn mission to determine the internal structure and composition of Ceres. The measurements came from observing the spacecraft's motions with NASA's Deep Space Network to track small changes in the spacecraft's orbit. This study is published in the Journal of Geophysical Research.

Ermakov and his colleagues' research supports the possibility that Ceres is geologically active—if not now, then it may have been in the recent past. Three craters—Occator, Kerwan and Yalode—and Ceres' solitary tall mountain, Ahuna Mons, are all associated with "gravity anomalies." This means discrepancies between the scientists' models of Ceres' gravity and what Dawn observed in these four locations can be associated with subsurface structures.

This animation shows dwarf planet Ceres as seen by NASA's Dawn. The map overlaid at right gives scientists hints about Ceres' internal structure from gravity measurements. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

"Ceres has an abundance of gravity anomalies associated with outstanding geologic features," Ermakov said. In the cases of Ahuna Mons and Occator, the anomalies can be used to better understand the origin of these features, which are believed to be different expressions of cryovolcanism.

The study found the crust's density to be relatively low, closer to that of ice than rocks. However, a study by Dawn guest investigator Michael Bland of the U.S. Geological Survey indicated that ice is too soft to be the dominant component of Ceres' strong crust. So, how can Ceres' crust be as light as ice in terms of density, but simultaneously much stronger? To answer this question, another team modeled how Ceres' surface evolved with time.

A 'Fossil' Ocean at Ceres

The second study, led by Roger Fu at Harvard University in Cambridge, Massachusetts, investigated the strength and composition of Ceres' crust and deeper interior by studying the dwarf planet's topography. This study is published in the journal Earth and Planetary Science Letters

By studying how topography evolves on a planetary body, scientists can understand the composition of its interior. A strong, rock-dominated crust can remain unchanged over the 4.5-billion-year-old age of the solar system, while a weak crust rich in ices and salts would deform over that time.

By modeling how Ceres' crust flows, Fu and colleagues found it is likely a mixture of ice, salts, rock and an additional component believed to be clathrate hydrate. A clathrate hydrate is a cage of water molecules surrounding a gas molecule. This structure is 100 to 1,000 times stronger than water ice, despite having nearly the same density.

The researchers believe Ceres once had more pronounced surface features, but they have smoothed out over time. This type of flattening of mountains and valleys requires a high-strength crust resting on a more deformable layer, which Fu and colleagues interpret to contain a little bit of liquid.

The team thinks most of Ceres' ancient ocean is now frozen and bound up in the , remaining in the form of ice, clathrate hydrates and salts. It has mostly been that way for more than 4 billion years. But if there is residual liquid underneath, that ocean is not yet entirely frozen. This is consistent with several thermal evolution models of Ceres published prior to Dawn's arrival there, supporting the idea that Ceres' deeper interior contains liquid left over from its .

Explore further

Dawn mission extended at Ceres

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User comments

Oct 26, 2017
Kowabunga, Dude!
Gnarly Surfing. I'm Sure!

Oct 27, 2017
Wouldn't it be exciting to actually explore Ceres in person?!

Oct 28, 2017
MT, better thee than me. But what the heck, we all gotta die sometime.

Yours could be epic level painful and degrading. As long as you make the headlines...Right? And get that footnote in the history books to boot. Gotta keep our priorities, for our life expectations, straight.

Oct 28, 2017
Probably active laser/phaser/other type beam defenses on Ceres.....main reason for 'reluctance to land there'!! If YOUR people had an industrial/defense/research operation there of a proprietary/security/military nature, would you defend it our just fade quietly away? No real way to totally leave there, as the installations maybe there for a long time, and alternative housing not ready quickly.... Or maybe something really valuable in/on Ceres and mining/processing/whatever operation will proceed. If Ceres is a staging area for military expeditions, then further surveillance will be required and a 'cover story' for a HUGE budget will BE necessary. That is budget in lives as well as equipment/materiel, etc. No reasonable earth alliance no matter how secret will be able to keep this secret for more than ten milliseconds after attacks on Earth begin. No person above the IQ of idiot with an AK to his head will really believe the 'salt reflection' story.

Oct 28, 2017
MT... exploratioin of Ceres best done initially just like it was first done... Quietly with a small probe sneaking out of the cold black of space with nary but the faintest glow of impulse electric thrusters. To physically explore it for caves or other means by which WE could live on an energy poor budget... no fusion reactors, no artificial gravity units, no electronic field shielding like the recent discovery will take the use of caves large enough to park surface transport. Ceres' natural gravity low, so probably Shawer drives would do, but Shawyer's stuff has new British patents now and with Chinese help too probably work better than most assume. We would need a true exploration ship, no less than 5,000 tonnes and crew of over 100 with landing bays, ag bays, machine shops, water and air treatment/recycle plants.... and... Shawyer powered SHUTTLES with airlocks and cargo holds. Ship must carry stuff to support live in colony for a year, include medical and dental, etc.

Oct 29, 2017
It's a rock.

Oct 30, 2017
As long as you make the headlines...Right? And get that footnote in the history books to boot. Gotta keep our priorities, for our life expectations, straight
admittedly there are plenty of people who would explore simply to be that historical footnote, but some people explore because it's in their nature to simply go out and do it... they don't care about history or the mark they leave

for instance: regardless of the european explorers who "found" the america's, australia, hawaii, etc, there were already explorers there who found it first

Oct 30, 2017
CS, you made some very good points. However, my peeve is with the guys who are commenting on the subject of exploration.

None of them are going to risk their flabby, white asses on those expeditions!

None of them are making any effort to invent, develop or manufacture the protective technology needed for manned flight.

Specifically making possible a real, self-sustained gravity field. And an energy field that collects and directs the extreme radiation beyond the Van Allen Belts.

Both of those physical inventions are absolutely needed for any long-term Human presence away from the Earth. Every other attempt at a manned expedition is a complete waste of time and funding, until both those efforts are proven successful.

Oct 31, 2017
None of them are going to risk their flabby, white asses on those expeditions!
some of us aint white though!

but back to the point
None of them are making any effort to
with the type of risk involved, you will need cannon fodder, so why not use those who have nothing to give but their willingness to be guinea pigs?

seriously - though most people talking here will likely just be talking sh*t to get attention, you need pawns in chess just as much as you need the other pieces if for no other reason than as a sacrifice
Both of those physical inventions are absolutely needed for any long-term Human presence away from the Earth

so, who better to test it on than the willing?

consider this like medical drug trials:
there is no guarantee of help, nor is there even a guarantee of said drug ever making it to market if it does help some folk

Oct 31, 2017
It is exasperating (to me) how callous people can be towards other peoples suffering and deaths. When I see any of youse guys lining up to volunteer to be the 'guinea-pig'? I might have more respect for your opinions.

First necessity will be an energy field that can gather and direct high energy radiation. Cause you don't want to bounce those accumulated cosmic-rays in the wrong direction. Such as, say ohh, a military defense satellite?

I do not see any reason preliminary development and testing cannot be done Earthside.

I admit, the ability to produce a Real Gravity field here on Earth would be a hell of a lot tougher. Unless some genius makes a really big breakthrough in theoretical sciences?

The only realistic method I can foresee is by producing degenerate matter. Applied as layers of paint to build up to a one-gee effect.

I suspect such a production facility would have to be in zero-gee orbit. Utilizing automated equipment and waldoes.

Oct 31, 2017
When I see any of youse guys lining up to volunteer to be the 'guinea-pig'? I might have more respect for your opinions
just FYI - have done and still do - voluntarily and non-voluntarily in some cases
I do not see any reason preliminary development and testing cannot be done Earthside
true that
except for the artificial gravity part... that will have to be done in orbit or in some similar environment

one problem that we will have is our evolution in a gravitational field - we will have to find a way to adapt because of that. we will also not be able to adapt well in log G until we can adapt ourselves quickly to low G (biomedically, physically or otherwise)

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