New type of 'space weathering' observed on asteroid Vesta

New type of 'space weathering' observed on asteroid Vesta
This image from NASA's Dawn spacecraft features the distinctive crater Canuleia on the giant asteroid Vesta. Canuleia, about six miles (10 kilometers) in diameter, is distinguished by the rays of bright material that streak out from it. There is also a more subdued unnamed crater of about the same size to the northeast. A comparison of these two craters illustrates how freshly excavated materials on Vesta appear quite different from background soils. The image was taken by Dawn's framing camera on Oct. 20, 2011, from an altitude of about 420 miles (680 kilometers). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/PSI/Brown

The surface of the giant asteroid Vesta is weathering in a way that appears to be completely different from any other asteroid yet visited, according to new data recorded by NASA's Dawn spacecraft. This new type of space weathering suggests that there's something about Vesta—perhaps its mineral composition or its position in the solar system—that makes its surface environment fundamentally different from other asteroids studied thus far.

The new data are presented in a paper published Nov. 1, 2012, in the journal Nature.

Space weathering is the term used to describe how the surfaces of airless bodies like asteroids and some moons change over time. The phenomenon was first identified on our own Moon. Soil ejected from fresh looks brighter than the surrounding background soil, often forming bright rays streaming away from the crater. It wasn't clear at first why newly exposed soil would look different.

As laboratory equipment improved, scientists eventually showed that soils darken over time on the because they are exposed to a constant barrage of tiny meteorites as well as from the sun known as the solar wind. As these materials interact with the surface, they produce a fine coating of that builds up on soil grains over time, darkening the soil. Deeply buried material lacks that coating, so when it's churned up by a large , it has a brighter appearance than the weathered soil.

This same type of space weathering involving metal nanoparticles was later found to occur on several asteroids as well.

New type of 'space weathering' observed on asteroid Vesta
This image from NASA's Dawn spacecraft shows a close up of part of the rim around the crater Canuleia on the giant asteroid Vesta. Canuleia, about six miles (10 kilometers) in diameter, is the large crater at the bottom-left of this image. This close-up image illustrates the structure of the interior of the crater and complex details of the fresh rays across the soil of Vesta. The image was taken by Dawn's framing camera on Dec. 29, 2011, from an altitude of about 130 miles (210 kilometers). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/PSI/Brown

"We thought we understood this pretty well," said Brown University geologist Carle Pieters, one of the original scientists to study the phenomenon. "That's space weathering." Or at least it was until the showed that Vesta, one of the largest bodies in the , weathers in a completely different way.

As on the Moon, soil ejected from craters on Vesta looks different from background soil, so it's clear that some kind of weathering is taking place on Vesta. But using Dawn's visible and infrared spectrometer, Pieters and colleagues found that weathered soil on Vesta doesn't have any of the nanophase metal that characterizes weathered soil on the Moon and some asteroids.

"We know that the surface of Vesta is weathering," Pieters said, "but it can't be happening in the same way as these other bodies."

Weathering on Vesta appears to happen through meteorite impacts that mix soils mechanically, not through creation of the nanophase metals like on the Moon. "Think of it like throwing a rock in a sandbox," Pieters said. "You're not altering the sand in any fundamental way. You're just tossing it around."

The trick now is figuring out why the nanophase weathering so pervasive on the Moon doesn't seem to happen on Vesta. One possibility is that the meteorites hitting Vesta don't vaporize as they often do on the Moon, or perhaps the solar wind is too weak out in the asteroid belt, making the formation of nanoparticles less likely, Pieters said. The prevalence of mechanical mixing could have something to do with how the gravitational characteristics of Vesta allows particles to move or with Vesta's initial .

"It could be a lot of things," Pieters said. "That's the next problem we're working on now."

Pieters also plans to go back and re-examine space weathering processes on the Moon and other asteroids.

"There are probably things we've overlooked on other asteroids because we've just been concentrating on the nanophase coatings," she said. "But Vesta has shown us that this mixing process is really very important."

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Image: Fresh impact craters on asteroid Vesta

Journal information: Nature

Provided by Brown University
Citation: New type of 'space weathering' observed on asteroid Vesta (2012, October 31) retrieved 18 July 2019 from
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Oct 31, 2012
It seems likely that they have examined the spectra of the reflected light from the ejecta rays, but I wonder if this might not be water ice that formed following the impact --perhaps this was a particularly water-rich area of Vesta that was struck?

Oct 31, 2012
4 km deep dust

Oct 31, 2012
"We thought we understood this pretty well," said Brown University geologist Carle Pieters.

Sigh. Narrow minded and arrogant. These assumptions about the accuracy of our current knowledge of the world around us, inhibit us from seeing so much.

Oct 31, 2012
"We thought we understood this pretty well," said Brown University geologist Carle Pieters.

Sigh. Narrow minded and arrogant. These assumptions about the accuracy of our current knowledge of the world around us, inhibit us from seeing so much.

Notice she was speaking in the past tense.

Nov 01, 2012
Ah, A2G..

It is super satisfying for me to see you write this on two different articles! Hopefully you are better with plasma than you are at playing detective, because I am not Hannes. I am not pro EU or standard model, or anything else. I am against people being tools, and you are a wonderful tool. As I said in my other response, if I can in any way prove that I am not Hannes I gladly will, just to shove it down your throat. In the mean time, please keep referring to me as other people, as I think it will be a joy for them to see you being such a schizo.

Meyer-As a scientist she should understand her limited perspective. Two hundred years from now humans would find this article to be science comedy..."Gasp! Sciencists are shocked as something different than expected has happened!." Kids with stethoscopes playing at doctors, IMO.

Nov 01, 2012
GW, what exactly did you want her to say then?
"All we had ever seen before was nanophase weathering, and now that we finally see a different type, we are totally not surprised and it is nothing interesting and it doesn't change our theories at all. Because instead of basing our theories on observed data, we just go with the Grand Theory of Everything: 'We don't know it all, we can never know it all, so why bother'"

Nov 01, 2012
The problem, A2G, is the refusal to consider alternative hypotheses and inferences when there exists the philosophical problem of unconceived alternatives. Unlike textbook problems, most real-world problems are ill-structured. When disciplines -- such as astrophysics and cosmology -- are so observationally and experimentally limited that speculations become unavoidable, we call them wicked problems. Since wicked problems lack sufficient detail for a single, certain right answer, the solution process is inherently argumentative. And to ensure long-term progress, the problem-solvers must actively avoid the premature consensus known as groupthink by continually raising questions and collaboratively exploring lines of argumentation which stem from competing hypotheses and inferences. The process is not simply a matter of applying an algorithm or formula; it's a data-driven, interdisciplinary, opportunistic, open-minded -- yet-critical -- process.

Nov 01, 2012
Technically speaking, the process is called Computer Supported Collaborative Learning. If you do a Google search on it or check out the handful of books on the topic, you will notice that they state the problem in the exact same way that I have here. Wicked problems are a generic type of problem, for which a generic set of issues and solutions have been observed & devised. Astrophysicists and cosmologists, however, are treating the problem as though it's simply a TECHNICAL challenge. The truth is that these disciplines rather obviously fall into the category of an ADAPTIVE change challenge insofar as they demand a multi-paradigm analysis -- including an eagerness to critique one's own preferred framework. The truth is that in two separate studies of around 500 people, Kegan and Lahey have identified that only 1% of the population is capable of this behavior.

And to be clear, that 1% exists at the top of Fortune 500 companies -- not in the fields of astrophysics nor cosmology.

Nov 01, 2012
If the physics discipline wanted to train their students to be self-transformative (ie, prepared to question their own frameworks), then they would first have to stop weeding out divergent thinkers in the PhD programs -- for those are the very people who ARE capable of such behaviors.

The decision to protect the hierarchy in the physics establishment comes at an extraordinary cost for both them and society, for it guarantees the unfortunate, ironic result that they will fail to train their students to solve the most persistently wicked problems we face in those disciplines. It's a little bit like the pharmaceutical industry which refuses to treat the root cause of illness, for it creates a dependency of society upon them while also guaranteeing that these wicked problems will never go away.

Nov 01, 2012
A2G, you might want to think very carefully about what you are supporting. We have 30 years of physics education research and cognitive science findings which is just waiting to be applied to our university system. A necessary part of these reforms, in order to get from our current theories to theories which work and are predictive, is to teach students how to think critically about scientific theories. Needless to say, you cannot teach critical thinking if you decide to present science as though there is simply one right answer. Monolithic science does not offer us an authentic means of teaching critical thinking. The only effective way to do that is to encourage students to practice re-framing problems -- in other words, to encourage them to compare and contrast frameworks like the Electric Universe and the conventional theories.

Whether or not the EU is more right than wrong is irrelevant for CSCL. It's the process of practicing argumentation which matters most.

Nov 01, 2012
A2G you seem to be getting more worked up than anyone else.
Why do you feel you have to be a comment watchdog for this website?
lf people want to focus on non-controversial physics then they have every ability to ignore one argument and focus on another. Even if there is a trend in this kind of posting, this is the internet. You cant expect people to follow all of the same rules and share the same general perspectives.

Nov 01, 2012

Whether or not the EU is more right than wrong is irrelevant for CSCL. It's the process of practicing argumentation which matters most.

What a load.

This is simply a "Digital Era" rebranding of what we are already familiar with as a "Think Tank".

And, we are all familiar with the all-to-often flawed results of applying conclusions arrived at via this process in the real world.

It is cetainly a legitimate construct in terms of searching for new ways of perceiving, defining and subsequently thinking about problems, but it lacks the one requirement that is fundamental to Science --empirical experiment with replicable results.

One can easily state that it is possible to, for example, levitate a given mass, but without actual demonstration of the process/principle, the assertion remains nothing more than so much smoke.

This is the central problem with your EUT --it remains unsupported by experimentally derived empirical support, and therefore renders your claims moot.

Nov 01, 2012

If you want to theorise about the EUT, that's fine. And if yu wish to work towards developing an experimental framework to demonstrate your hypothesis --so much the better. I'm sure we would all benefit from such an endeavor --one way or another.

Meanwhile, we are constantly subjected to this maneuvering around the issue, unsubstantiated assertions about our incorrect understanding of cosmological processes, and the use of Academic inertia as a last-resort defense of your unsupported claims, and expect everyone here to buy what you are selling.

When you have the kind of experimentally-derived evidence required by science to support your theory, then and only then can you expect any acceptance of it here.

Nov 05, 2012
Ah, the EU cranks again. They, like creationists, shouldn't comment on science blogs.

Both ideas have had centuries to turn up successful predictions that can rival current science. They can't, so these rejects don't belong here.

If they, against all likelihood, can get a science started they would be welcome to compete on the market of ideas publications, press releases and science blogs discussing it. But that won't happen.

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