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Vesta Rocks

Explanation: These colorful images are of thin slices of meteorites viewed through a polarizing microscope. Part of the group classified as HED meteorites for their mineral content (Howardite, Eucrite, Diogenite), they likely fell to Earth from 4 Vesta, the mainbelt asteroid currently being explored by NASA's Dawn spacecraft. Why are they thought to be from Vesta? Because the HED meteorites have visible and infrared spectra that match the spectrum of that small world. The hypothesis of their origin on Vesta is also consistent with data from Dawn's ongoing observations. Excavated by impacts, the diogenites shown here would have originated deep within the crust of Vesta. Similar rocks are also found in the lower crust of planet Earth. A sample scale is indicated by the white bars, each 2 millimeters long.

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The polarizing microscope picture really looks somewhat psychedelic.

Nice pictures of rocks from Vesta. The rock on the right though bothers me since some of the crystalline structure is poly-chromatic. Its been a couple decades since doing similar samples and don't remember why that occurs. The light source is polarized so the sample maybe isn't perfectly flat along that edge? My experience is only among alloys of metals and our samples didn't produce these multi-
colored effects as i recall. Anybody know?
Arne

Anybody know?...
Well talking to my shadow; but, assuming the material is stressed then this color distribution looks like stress birefringence because it occurs along the edge of the sample. When i let my fingers do the walking then Wiki came along with the talking and filled me in. This assumes the material is flat which might occur if the mineral is hard and the media used to mount the sample before slicing was softer.

Beyond wrote:The polarizing microscope picture really looks somewhat psychedelic.

Vesta Rocks, baby! Yes she does!
Even her acne scars are 'cause
She's totally blown away (well half of her)

Hmm maybe needs work

How much cheaper it was to get a physical sample of Vesta, than to go there to take pictures of its surface? A billion times cheaper?

Not being familiar with HED meteorites, I have to admit 'diogenite' was a completely new word on me (...I mean honestly, where've I been all these years!) . . . could have maybe done with providing us with a link on that word too, but I looked it up anyway. So, I gather that it is quite a commonly used word, but just not in my vocabulary. Fascinated by the pattern of fracture lines (if that is what they are?) Going purely on appearances, if I had to choose between these two thin samples, I'd take the one on the right . . . it shows great polarised colours!

henrystar wrote:How much cheaper it was to get a physical sample of Vesta, than to go there to take pictures of its surface? A billion times cheaper?

How much more we would know if we got to see an asteroid that we don't know much about? Or which asteroid this came from?

APOD Robot wrote: Similar rocks are also found in the lower crust of planet Earth.

So; is it possible that these samples may have come from in Earth's lower crust?

It looks like a colored thematic map (of geology or nature of the ground or so - on the left an area with streets and cities, on the right a natural area with rivers)

orin stepanek wrote:

APOD Robot wrote: Similar rocks are also found in the lower crust of planet Earth.

So; is it possible that these samples may have come from in Earth's lower crust?

As I understand it (and I am by no means an expert), these samples are confirmed meteorites and so not of Earth.

I just love this site. You don't just see thin slices of meteorite through a polarized microscope everyday.

Doink wrote:

orin stepanek wrote:

APOD Robot wrote: Similar rocks are also found in the lower crust of planet Earth.

So; is it possible that these samples may have come from in Earth's lower crust?

As I understand it (and I am by no means an expert), these samples are confirmed meteorites and so not of Earth.

Come to think of it, I suppose it's possible that a big enough impact or explosion could have launched material from Earth's lower crust into space wherefrom it eventually fell back to earth to become these meteorites. I guess we'll just have to wait and see what spacecraft Dawn tells us to (maybe) know for certain.

Quibble:

"Part of the group classified as HED meteorites for their mineral content (Howardite, Eucrite, Diogenite), ..."

This makes it sound as if Howardite, Eucrite, and Diogenite are types of minerals. I know this is not what was intended, but the wording is ambiguous. Rather:

"Part of the group classified as HED (Howardite, Eucrite, Diogenite) meteorites, based on their similar mineral content (clinopyroxene, plagioclase,olivine).

moonstruck wrote:I just love this site. You don't just see thin slices of meteorite through a polarized microscope everyday.

That's what makes This Place Fun! You never know what you'll get to see. Why even Shakespeare shows up in some of the darnedest places

Hi all, I took these pictures and the text was adapted from a piece I wrote for the Dawn team, so I will try I answer some of the questions.

First and foremost, I encourage you to browse through the Dawn Image of the Day archive on the Dawn team website for more information about HED meteorites and Vesta. The two images are different colors due to variance in mineralogy.  The meteorite on the left is all orthopyroxene (brown and greyscale) while the sample on the right is orthopyroxene and olivine (more colorful).  The change in olivine color towards the rim is due to change from a more Mg-rich core to Fe-rich rim.  This is called zoning. It may also be caused by change in section thickness.

We know these sample did not come from Earth because they are isotopically distinct from Earth rocks.  That, and they fact that they were recovered in Antarctica, sitting on the ice and covered in fusion crust, a shell the forms around meteorites when they pass through the Earth's atmosphere.

I would be happy to answer any other questions people may have!

Zarathoostra wrote:I would be happy to answer any other questions people may have!

Ok then. What minerals do you see that might be worth mining? I'm a sci-fi artist so I'm thinking centuries in the future when it would be economically feasible and all that. Would minerals like gold have seams like they do on Earth or is that caused by geological activity? Are there heavier elements like Uranium (I'm a proudly nuclear-free New Zealander but I see no problem with it out in space where radiation levels are already deadly)?

As far as mining asteroids goes, I am afraid there is not too much in the rocks that would be worth mining. High concentrations of gold specifically require geologic conditions that are pretty unique to Earth. There are other elements that we find in abundance in the cosmos that we don't find on Earth, which may be utilized some day. For example, He3, a very important element in nuclear fusion, is thought to be in much greater abundances on the Moon than on Earth.

Thank you. Of course you mention Mg and Fe which could be used in alloys to build the hulls of spacecraft and space stations, perhaps?

Then I'm sure you can find H₂O, O₂ and N₂ for an atmosphere. All you need then is food, which would have to be foul-tasting muck with some hydroponically-grown vegetables.

Flase wrote:Thank you. Of course you mention Mg and Fe which could be used in alloys to build the hulls of spacecraft and space stations, perhaps?

There are many things in asteroids that might be worth mining if we were doing a lot of major construction in space. In that case, it isn't that these are intrinsically valuable materials, just that it is very expensive to get them out of Earth's gravity well and into space. But given the infrastructure necessary to set up mining on asteroids, it would have to be a pretty major presence in space we were supporting- something that I don't see happening in the next few decades, and probably not even the next century.

Took a look at that, and thought immediately, "This has to be proof of the 'gravel-bank' idea of asteroid structure!"
All those individual pieces, in one rock. It's like a sandstone, particles compressed together!

But in fact, this appearance is not evidence that the rock is compressed sand or gravel. It's an artifact of the thin-section process.
This site: http://www.earth.ox.ac.uk/~oesis/micro/ specilises in thin-section views of rocks.
Sure, the sandstones look like this - but so do the granites!
Only the metamorphic rocks look at all homogenous under the microscope.

I say so myself, but this would have been really useful information to put intothe APOD caption.

John