Space

25-mile-deep reservoir of salty water found beneath surface of Ceres

25-mile-deep reservoir of salt...
A mosaic image using false color to highlight the exposed brine on the surface of Ceres
A mosaic image using false color to highlight the exposed brine on the surface of Ceres
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A mosaic of the Occator Crater, on the surface of dwarf planet Ceres
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A mosaic of the Occator Crater, on the surface of dwarf planet Ceres
A mosaic image using false color to highlight the exposed brine on the surface of Ceres
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A mosaic image using false color to highlight the exposed brine on the surface of Ceres

Through its 11-year stint studying the asteroid belt between Mars and Jupiter, NASA’s Dawn mission has profoundly changed our understanding of the dwarf planet Ceres. New analysis of data collected during the latter stages of this mission has offered some compelling answers to long-standing questions about the makeup of Ceres, starting with presence of a 25-mile-deep reservoir of brine beneath the surface.

Over the past few years as data from the Dawn mission continued to roll in, scientists have been piecing together a puzzle of peculiar geological activity on Ceres. The nature of unusually bright spots that feature in its Occator Crater posed a mystery, with scientists working to understand how they are formed and what they might represent.

Evidence had suggested that these deposits are formed by salty liquid bubbling up to the surface to leave the highly reflective deposits on the crust, but where could such a liquid come from? While an underwater reservoir of brine was seen as a strong possibility, the discovery of new evidence has now led scientists to conclude not only that this is indeed the case, but that ongoing geological activity is keeping these salty surface features fresh and shining brightly.

The environment of Ceres’ surface is one where salts holding water would be expected to dehydrate in just a matter of centuries. But the team found salt compounds concentrated in one of the better-known bright spots, called Cerealia Facula, that were still carrying water, suggesting that they must have made their way to the surface only recently. According to principal investigator for the Dawn mission, Carola Raymond, the pathways for this process could be traced back to the crater impact millions of years ago.

"For the large deposit at Cerealia Facula, the bulk of the salts were supplied from a slushy area just beneath the surface that was melted by the heat of the impact that formed the crater about 20 million years ago," she explains."The impact heat subsided after a few million years; however, the impact also created large fractures that could reach the deep, long-lived reservoir, allowing brine to continue percolating to the surface."

A mosaic of the Occator Crater, on the surface of dwarf planet Ceres
A mosaic of the Occator Crater, on the surface of dwarf planet Ceres

Adding further support to the idea of liquids on Ceres was the discovery of small hills resembling pingos here on Earth, which are small icy mountains found in the polar regions that are created by pressurized groundwater. These had been seen on Mars before but never on a dwarf planet.

The team also carried out new gravity measurements of Ceres using the latest data from Dawn, revealing that the brine reservoir is around 25 miles (40 km) deep, and hundreds of miles wide. These gravity measurements also offered new insights into the dwarf planet’s interior, finding that its crustal density increases with depth. This increase in density is much greater than could be explained by pressure alone, so the team believes that it is the result of the underground reservoir incorporating salt and mud into the lower crust as it freezes.

"Dawn accomplished far more than we hoped when it embarked on its extraordinary extraterrestrial expedition," says Mission Director Marc Rayman of NASA's Jet Propulsion Laboratory in Southern California. "These exciting new discoveries from the end of its long and productive mission are a wonderful tribute to this remarkable interplanetary explorer."

Three papers describing the discoveries were published in the journals Nature Communications, Nature Geoscience and Nature Astronomy.

Source: NASA

4 comments
Chris Coles
What everyone needs to understand is that the internal force structure, created by the principle of all atoms, indeed, all protons, within any solid mass object, no matter how large or small; attract each other relative to their own mass. Remembering that as all the internal mass is directly in contact with every surrounding particle of mass; then the force, gravity, within that mass, is always a negative force towards each particle of mass, and thus the structure of the forces with mass are always observed as towards the centre of the mass at the surface, (attracted towards the surface of the mass); while at one end the same moment, at the very centre of the mass, those forces meet from every direction to form a point of equilibrium that cannot be crossed, and, as such; must conform to Newton's third law, where every force must have an equal and opposite action right at that point of equilibrium; in turn, meaning that right at the centre of the mass, gravity is towards the surface, in every direction from that central point of equilibrium. Now, as you can observe a force from the surface towards the centre, and at the same moment, a force towards the surface at the centre; then there must also be a shell of equilibrium of the forces, between the surface and the centre, within the mass; the location of which will directly relate to the density of the mass wherever it is located within the object. It is therefore important that everyone recognises that such an internal gravitational force structure will also dictate the location of internal structures such as the 25 mile deep reservoir of salty water on Ceres. Food for thought?
Username
Chris, your point of equilibrium is the dead center where you are pulled equally in all directions. Any place else the mass distribution around you will not be equal.
Readout Noise
"Username" is correct. There is no shell, between centre and surface, where the gravitational forces balance out. The description given by Chris ignores the fact that any particle in such a shell experiences a gravitational pull from _all the matter on the far side_ of the centre, as well as from the matter between the particle and the centre. This is much greater than the pull on the particle from only the matter above it, between the shell and the surface.
Chris Coles
Username and Readout noise are both reacting to what has, since Newton, been accepted theory. However their theory has been shown to be wrong, both in a logical debate, and since then, twice demonstrated. The first paper, presented to the Royal Society in London 2011 titled; Visual Proof of Balanced Forces in Equilibrium, the second; Balanced Force Demonstration. the first used a length of elastic, which prompted a girl in a BBC Horizon program to suddenly step forward out of the shadows with a wide length of elastic upon which were spaced stars, which she then stretched out with a smile and then disappeared back into the shadow. Presumably the BBC way of giving two fingers to new fact.
neither paper has produced any result; it would appear that today, facts; indeed, demonstrable facts; are never to be accepted, only ridiculed.

may I ask both of you to go read Principia where you will find these two, seeming never appreciated statements by Newton. In Definition 1. he writes: "I have no regard in this place to a medium, if any such there is, that freely pervades the interstices between the parts of bodies. It is this quantity that I mean hereafter everywhere under the name of body or mass" Thus we see that he makes it clear he does not have an interest in the internal properties of any solid mass; he simply calls it a body or mass.

In Definition VIII he writes; "For I here design only to give a mathematical notion of these forces, without considering their physical causes and seats". Ergo, his real interest is mathematics; he is thus less concerned with any underlying physical aspects of the debate and he continues:

"I likewise call attractions and impulses, in the same sense, accelerative, and motive; and use the words attraction, impulse or propensity of any sort towards a centre, promiscuously, and indifferently, one for another, considering these forces not physically, but mathematically; wherefore, the reader is not to imagine, that by these words, I anywhere take upon me to define the kind, or the manner of any action, the causes or the physical reason thereof, or that I attribute forces, in a true and physical sense, to certain centres (which are only mathematical points); when at any time I happen to speak of centres as attracting, or as endued with attractive powers." (Taken from chapter 13.3 Newton defines rules for mathematics; not structure; The Universe is a Cloud of Surplus Proton Energy) . . . which is presently unavailable.