Asteroid approach, Science operations begin! |
Asteroid approach, Science operations begin! |
Mar 20 2019, 02:06 PM
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#61
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Senior Member Group: Members Posts: 1582 Joined: 14-October 05 From: Vermont Member No.: 530 |
You mention thermal and mechanical/gravity. There's also electrostatic...
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Mar 20 2019, 02:09 PM
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#62
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
Agreed, electrostatic charging due to solar UV may do it, as well. Even a weak repulsive force would be sufficient. I think, that 10V are considered reasonable in direct sunlight. Impacts of micrometeorites might be another approach. Tracking particles, and their acceleration due to solar radiation pressure and some potential weak electrostatic field could clarify the physics at work. Those fields would change with solar irradiation.
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Mar 20 2019, 07:11 PM
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#63
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Member Group: Members Posts: 435 Joined: 14-December 15 Member No.: 7860 |
Or maybe Bennu is a body reassembled from fragments scattered after a relatively recent breakdown by impact and it is still undergoing a rearrangement of its surface (creation of the equatorial ridge) under the influence of its own gravity. Such small surface movements could throw small particles into space (?)
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Mar 21 2019, 12:56 PM
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#64
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Newbie Group: Members Posts: 11 Joined: 13-May 15 Member No.: 7464 |
Image processing artifacts or a lot more particles orbiting around Bennu?
Cranked up brightness levels in original image https://www.asteroidmission.org/?attachment_id=15595 |
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Mar 21 2019, 03:14 PM
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#65
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Senior Member Group: Members Posts: 4246 Joined: 17-January 05 Member No.: 152 |
Recall that that press release image was a composite of two frames, differing by a factor of a few thousand in shutter speed. So if you're referring to the arc of bright pixels reaching clockwise around Bennu from the main "jet", the sharpness of that arc's inner edge suggests that edge is the splice between the two frames. Since the outer exposure was much longer, it was probably picking up some glare from the main asteroid's body, which appeared as a sprinkling of bright pixels.
The main "jet" would appear much, much fainter (or be invisible) if this was a single exposure. |
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Mar 21 2019, 06:17 PM
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#66
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Newbie Group: Members Posts: 11 Joined: 13-May 15 Member No.: 7464 |
Since the outer exposure was much longer, it was probably picking up some glare from the main asteroid's body, which appeared as a sprinkling of bright pixels. Thx, yes, I guessed just as much. The other composite (posted here yesterday) shows the glare and the thorough identification process by the team, this wouldn't have escaped them. "Jet" particle sizes were said to be cm size, even as much as 30cm. |
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Mar 21 2019, 08:04 PM
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#67
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Member Group: Members Posts: 149 Joined: 18-June 08 Member No.: 4216 |
if memory serves, the charge-to-mass ratio of cm-sized particles would be far too low for electrostatic forces to play a role. This is some combination of day-to night thermal cycling + rotational state + composition.
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Mar 27 2019, 05:41 PM
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#68
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Junior Member Group: Members Posts: 80 Joined: 18-October 15 From: Russia Member No.: 7822 |
This 3D visualization is based on my preliminary 3D shape model and data taken by NASA's OSIRIS-REx spacecraft.
https://youtu.be/QRWdBoQm7J0 -------------------- |
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Mar 27 2019, 07:11 PM
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#69
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Solar System Cartographer Group: Members Posts: 10157 Joined: 5-April 05 From: Canada Member No.: 227 |
Very nice!.
Here is a map of Bennu. The main part of the surface is derived from a map on the mission website which extends from 70 N to 70 S. I had to fudge the poles (as we cartographers say) from other images. A couple of rocks have informal names (The Gargoyle is one of them), which I will add when I figure out where they are. If anyone knows of any other informal names let me know. The map projection is the same as I used for the Ryugu map, as they are so similar in shape. Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Mar 27 2019, 08:46 PM
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#70
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
Nice map! I believe that the rock at 45S 130E is "Ben-Ben." https://twitter.com/elakdawalla/status/1079919898514485248
-------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Mar 27 2019, 10:09 PM
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#71
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Senior Member Group: Members Posts: 1074 Joined: 21-September 07 From: Québec, Canada Member No.: 3908 |
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Apr 7 2019, 05:04 PM
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#72
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Member Group: Members Posts: 435 Joined: 14-December 15 Member No.: 7860 |
New pictures on the OSIRIS-REx website:
Bennu’s Equatorial Ridge - https://www.asteroidmission.org/20190329-fb4-equator-view/, Global Mosaic with a coordinate grid - https://www.asteroidmission.org/bennu-sides...-global-mosaic/ , 3D view from Laser Altimeter (OLA) measurements - https://www.asteroidmission.org/bennu-visua...d-by-ola-large/ and collection of 7 Nature papers (free and with many interesting pictures and conclusions) - https://www.asteroidmission.org/?latest-new...llection-nature |
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Apr 7 2019, 07:22 PM
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#73
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Member Group: Members Posts: 435 Joined: 14-December 15 Member No.: 7860 |
Two Bennu's pictures ( https://www.asteroidmission.org/20190329-fb4-equator-view/ and https://www.asteroidmission.org/?attachment_id=15551#main), turned, cropped and brightened (as Bennu is very dark) - give a bit of sense of view from above the surface
I added a scale For future astronauts, the terrain would be difficult to move around (large boulders everywhere), and microgravity would probably not help walking (constant danger of "flying away" into space) I think it would be a bit like trying to walk on the bottom of the sea with an oxygen bottle on your back. This would require lengthy practice. And no one, even a large rock, gives support, because it can "fly away" with you. Anyway, big boulders, carelessly pushed too much and fluttering around your head is quite scary vision. |
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Apr 11 2019, 10:21 PM
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#74
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Member Group: Members Posts: 435 Joined: 14-December 15 Member No.: 7860 |
Interesting photos from OSIRIS-REx:
really huge boulder in the northern hemisphere - https://www.asteroidmission.org/20190307-po...rthern-boulder/ cracked boulders on the equator - https://www.asteroidmission.org/20190307-po...m-cracked-rock/ I changed the first one slightly |
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Apr 12 2019, 07:47 PM
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#75
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Member Group: Members Posts: 435 Joined: 14-December 15 Member No.: 7860 |
More beautiful boulders: https://www.asteroidmission.org/20190307-so...boulder-region/
(I love big boulders in small worlds ) Many meteor collectors (including me) would like to have such "pebble" - it is CM chondrite, like Murchison (or something very similar) |
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