Giant mud balls roamed the early solar system
The earliest asteroids were probably made of mud, not rock. Radioactive heat in the early solar system could have melted globs of dust and ice before they had a chance to turn to rock [open, DOI: 10.1126/sciadv.1602514] [DX], a new simulation published July 14 in Science Advances shows. The results could solve several puzzles about the composition of meteorites found on Earth and may explain why asteroids are different from comets.
[...] Bland reasoned that heat from radioactive decay would melt the ice, and the resulting body would be an enormous dollop of mud. The mud would suspend sediment particles, so they wouldn't be stripped of their sunlike elements. And it would allow the early asteroids to be any size and remain cool.
Bland and Bryan Travis of the Planetary Science Institute, who is based in Los Alamos, N.M., ran computer models of how the mud balls would evolve. Convection currents, like those that move molten rock within the Earth's mantle, would develop, helping to transfer heat into space, the models showed. After several million years, the ball would harden completely, yielding the asteroids seen today.
NASA will make a decision within the next two months on whether to extend the Dawn mission to another asteroid, leaving Ceres.
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Dawn Finds Possible Ancient Ocean Remnants at Ceres
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 ocean. 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.
Constraints on Ceres' internal structure and evolution from its shape and gravity measured by the Dawn spacecraft (open, DOI: 10.1002/2017JE005302) (DX)
The interior structure of Ceres as revealed by surface topography (DOI: 10.1016/j.epsl.2017.07.053) (DX)
Previously: Dawn Spies Magnesium Sulphate and Possible Geological Activity on Ceres
Ceres's Cryovolcanoes Viscously Relax Into Nothingness
Organic Molecules Found on Ceres
Early Asteroids May Have Been Made of Mud Rather Than Rock
Dawn Mission Extended at Ceres
NASA's Dawn Mission to Asteroid Belt Comes to End
NASA's Dawn spacecraft has gone silent, ending a historic mission that studied time capsules from the solar system's earliest chapter.
Dawn missed scheduled communications sessions with NASA's Deep Space Network on Wednesday, Oct. 31, and Thursday, Nov. 1. After the flight team eliminated other possible causes for the missed communications, mission managers concluded that the spacecraft finally ran out of hydrazine, the fuel that enables the spacecraft to control its pointing. Dawn can no longer keep its antennae trained on Earth to communicate with mission control or turn its solar panels to the Sun to recharge.
The Dawn spacecraft launched 11 years ago to visit the two largest objects in the main asteroid belt. Currently, it's in orbit around the dwarf planet Ceres, where it will remain for decades.
Also at Ars Technica, The Verge, and Science News.
Previously: NASA's Dawn Spacecraft Nears the End of its Mission
NASA Retires the Kepler Space Telescope after It Runs Out of Hydrazine
Related:
Pluto and Ceres
After Eight Years, NASA's Dawn Probe Brings Dwarf Planet Ceres Into Closest Focus
NASA's Dawn Orbiter Finds a Mountain on Ceres
Dawn Spies Magnesium Sulphate and Possible Geological Activity on Ceres
Ceres' Cryovolcano Ahuna Mons Formed in the Geologically Recent Past
Ceres's Cryovolcanoes Viscously Relax Into Nothingness
Organic Molecules Found on Ceres
Early Asteroids May Have Been Made of Mud Rather Than Rock
Dawn Mission Extended at Ceres
Ceres May Have Had a Global Surface Ocean in the Past
Bright Areas on Ceres Suggest Geologic Activity
Dawn's Orbit Around Ceres: A New Low
Dawn's Orbit Around Ceres: First Images
Dawn Spacecraft Captures Closest-Ever Images of Ceres' Shiny Occator Crater
(Score: 2) by kaszz on Saturday July 15 2017, @03:49AM (6 children)
So this means asteroids were originally comets mixed with short lived radioactive substances that enabled them to shed all their fluid content (water) into space? If there were radioactive substances with short half-times, then there ought to be substances with longer half-times too ie Uranium etc?
This should then result in asteroids where the distribution of materials are quite even due to convection currents suspending particles like an emulsion. Which could serve to falsify the proposed mechanism.
And there should be free floating water molecule clouds in space? though it's likely it has been pulled into some deep gravity well.
If there's Uranium in most asteroids albeit at a low rate like 0.3% then a half cubic meter would be enough to fuel a reactor in space for use say on Mars etc.
(Score: -1, Troll) by Anonymous Coward on Saturday July 15 2017, @04:24AM
Inject Elon's cum into comets to revitalize the cosmos!
(Score: 2) by bzipitidoo on Saturday July 15 2017, @04:57AM (3 children)
What I wonder is, shouldn't most asteroids be nearly spherical, with their matter separated into layers of progressively denser material towards the core, just like planets, if they started as something as flexible as mud?
(Score: -1, Offtopic) by Anonymous Coward on Saturday July 15 2017, @05:41AM
You are overthinking this, bzipitidoo. Do you think that mud, exposed to the vacuum and (near) absolute zero conditions of space, could have condensed into delicious layers of vanilla, chocolate, and pistaschio, like planets do? Of course not! Flash freezing produces homogenuous bodies, frozen in time, and not exactly round or even spherical, because, you know, the universe is only 6,000 years old, so there was not time for this. It is all in my "bag of rocks" at "Assholes in Genesis"! Oh, and: the earth is flat, because it looks that way, the Earth is the center of the Universe, because Einstein said and even though he was a Jew it fits my Anthropogenic Global Centric theory. Oh, and, Gravity is not real, the Universe works on Russian Electricity, and that is what produce the Craters on the moon and sean hannity is wright that the main stream meidal is tryoing to destroyp; trumpldjlgj an chem-trails. jkfjljf slLOck here Up LOck her ups and omg bohica ptsd for all the Armenian, I mean American, kardashian, omg, look at her butt! I cannot lie, I am Republican, and I am insane. Please, help me. Impeach the bastard.
(Score: 2) by kaszz on Saturday July 15 2017, @08:16AM (1 child)
I don't interpret the articles finding that way. Small masses in free space means microgravity at most. And the convection currents should mix all of it continuously while at the same time making any fluid evaporate. When there's no fluid left it will be as it was, ie mixed. The non-spherical shape may come from being smashed by other objects and ripped apart by gravity wells.
(Score: 3, Interesting) by deimtee on Saturday July 15 2017, @12:33PM
If you haven't got enough gravity for density separation then you aren't going to get convection either. They are basically the same mechanism, with density changes due to different materials being a much stronger effect than temperature-related density changes.
I would surmise that you would only get convection within layers of otherwise uniform density. i.e. after a while you would have a core of heavy metals, a thick layer of rock shading into silt, then the layer of water. The water would presumably boil off into space.
Would possibly explain really high % nickel-iron meteorites, they are parts of cores of smashed asteroids with all the rock knocked off.
If you cough while drinking cheap red wine it really cleans out your sinuses.
(Score: 0) by Anonymous Coward on Saturday July 15 2017, @03:33PM
Every time NASA has done a fly-by (or a drive-by [nasa.gov]) of comets, no ice has been detected on or in the comet. (Water/ice is detected in the tail, but as the source has not yet been solely on the comet itself, it is apparently being generated by a different energetic process.)