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Asteroid approach, Science operations begin!
Marcin600
post Mar 20 2020, 10:04 AM
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Another example of surprisingly geometric shapes of boulders on Bennu
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Phil Stooke
post Mar 20 2020, 04:08 PM
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Marcin600 - yes, I just noticed the mosaic has been released without names. When I can get to it I will put it in my map.

Phil


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... because the Solar System ain't gonna map itself.
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Marcin600
post Mar 20 2020, 10:13 PM
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QUOTE (Phil Stooke @ Mar 20 2020, 05:08 PM) *
Marcin600 - yes, I just noticed the mosaic has been released without names. When I can get to it I will put it in my map.

Phil


I get it (I gave the link just in case). Me and many people are waiting for your works - they are always perfect ! smile.gif

Marcin

Ps. Is it possible to make polar projections (maps) from the materials you have so far from OSIRIS-REx?
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Phil Stooke
post Mar 21 2020, 08:05 PM
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Polar projections...


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These are not full polar hemispheres, they extend from 60 degrees N and S to the pole. Later I will make versions with grids, and full polar hemispheres. These are using the new mosaic.

Phil



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Marcin600
post Mar 22 2020, 04:47 AM
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QUOTE (Phil Stooke @ Mar 21 2020, 09:05 PM) *
Polar projections...


Attached Image



These are not full polar hemispheres, they extend from 60 degrees N and S to the pole. Later I will make versions with grids, and full polar hemispheres. These are using the new mosaic.

Phil


Wow! How fast! ohmy.gif You're the best!
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mcaplinger
post Mar 25 2020, 03:52 AM
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Here's some more info about Natural Feature Tracking.

https://www.nasa.gov/feature/goddard/2020/b...hine-as-beacons

Somehow, this blurb completely omits describing the camera being used for NFT or the organization that built it. mad.gif

As far as I can tell, the plan is still to execute the first TAG rehearsal in April.

At some point we may want a new thread.


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Disclaimer: This post is based on public information only. Any opinions are my own.
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Phil Stooke
post Mar 28 2020, 09:27 PM
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Here is a new map using the recently-released mission map as background.

Phil

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Phil Stooke
post Mar 31 2020, 08:57 PM
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https://astrogeology.usgs.gov/news/nomencla...roved-for-bennu

A new set of names for Bennu's rocks, added to those already given. I will get them on the map as time permits. Nice to see Thorondor among them, me being a Tolkien addict from way back.

Phil


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Phil Stooke
post Mar 31 2020, 09:32 PM
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Time permitted. New map, new names.

Phil

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Phil Stooke
post Apr 4 2020, 06:42 PM
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OK, now I'm adding the locations of the three particle ejection events reported so far.

Phil

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chuckclark
post Apr 5 2020, 12:40 PM
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Hmm. Three. And all in the same hemisphere. Ain't that kinda curious . . .

Three debris fields . . . hmm again:

Let's abstract the situation: Three relatively closely spaced points on a roughly spherical object make a triangle.
Now toy with it . . . connect each point with the center of its opposing side to find the triangle's centroid (where the lines intersect inside the triangle); extending those lines across [around?] the opposite hemisphere determines another point of intersection.

Use this antipodal intersection point to interrupt the surface and "unpeel" it along those extended medians a little bit——say 30 arc-degrees so we stay well distant from the debris fields——and use that extent of unpeeling-the-orange to create a Constant-Scale Natural Boundary map well suited to comprehensively study the debris fields and their interactions if any.

Alternatively, assuming no access to CSNB software, use
1) the antipodal point as the edge of an azimuthal equidistant projection to get a standard map crudely suitable for the same purpose, with severe distortion causing trouble only within say 30 of the map's edge. This won't be a problem if semi-orbital dust transport is not in play. The severe edge distortion can be eliminated by
2) an Oblique Peirce Quincuncial projection centered on the nearside centroid, rotated so the cross is a best fit with the medians. You'll get four far-side 45 "flaps" instead of the three 30 flaps you'd get with CSNB, so expect some map-edge interruption of the debris fields if semi-orbital dust transport is occurring. This could be minimized by
3) Setting up a digital 3-D model and glancing back and forth between it and either of the imperfect conventional maps and——assuming you've got above-average short-term memory——thereby sniffing out airborne debris interactions if any.

Just thinking out loud while Sopranos S2 E13 loads . . .
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Quetzalcoatl
post Apr 7 2020, 03:13 PM
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Greetings to you all,

Looking back on two recent images of Bennu proposed by Marcin:

http://www.unmannedspaceflight.com/index.p...st&id=45133

http://www.unmannedspaceflight.com/uploads...99384_thumb.png

I'm not a geologist, but I know the cleavages and cleavage planes in mineralogy or crystallography, the sometimes surprising forms that nature offers us and all things proper to cause our perplexity.

For the case of these geometric forms on this scale, present on a rubble pile, does anyone have explanations, hypotheses or even ideas that would distance us from mere chance?

Are you aware of other similar examples in the large catalogue of spatial imaging of asteroids?
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john_s
post Apr 7 2020, 10:09 PM
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Straight-line fractures ("joints") are pretty common on Earth- here's one example. They are a natural result of tectonic or other stresses in homogeneous rocks, and are different from the cleavage patterns you see in single crystals. The interesting question is what type of stresses (impact? thermal?) might do this on an asteroid surface.

John
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JRehling
post Apr 8 2020, 08:20 AM
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Bennu originated as a fragment of a larger body, so both the breakup event and the possible forces within the parent body seem to be more likely sources of fractures than anything that would occur in a body the size of Bennu.
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Quetzalcoatl
post Apr 8 2020, 10:44 AM
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QUOTE (john_s @ Apr 7 2020, 11:09 PM) *
Straight-line fractures ("joints") are pretty common on Earth- here's one example. They are a natural result of tectonic or other stresses in homogeneous rocks, and are different from the cleavage patterns you see in single crystals. The interesting question is what type of stresses (impact? thermal?) might do this on an asteroid surface.

John


Thank you very much John for your answer.

The Earth example you give us to see is spectacular and I know of others quite similar for our planet:

https://upload.wikimedia.org/wikipedia/comm..._Damaraland.JPG

http://cirquedebarrosa.free.fr/Images/robdiaclase6.JPG

But the context and the training processes are well known, there is no mystery. I never thought of comparing the large rock fractures on Bennu with crystalline cleavages. I was simply referring to natural geometries.

It is the observation that you make at the end of your intervention, specific to asteroids, that intrigues me. The question can indeed be asked about the type of stress but perhaps also about the type of rock involved (or at least some of its characteristics).
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