Asteroid approach, Science operations begin! Options

[stevesliva]

You mention thermal and mechanical/gravity. There's also electrostatic...

[Gerald]

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.

[Marcin600]

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 (?)

[bsharp]

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

[fredk]

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.

[bsharp]

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.

[tolis]

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.

[Roman Tkachenko]

This 3D visualization is based on my preliminary 3D shape model and data taken by NASA's OSIRIS-REx spacecraft.

https://youtu.be/QRWdBoQm7J0

[Phil Stooke]

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

[elakdawalla]

Nice map! I believe that the rock at 45S 130E is "Ben-Ben." https://twitter.com/elakdawalla/status/1079919898514485248

[charborob]

Bennu boulder in 3D.

[Marcin600]

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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[Marcin600]

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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[Marcin600]

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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[Marcin600]

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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