Asteroid approach, Science operations begin! |
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Asteroid approach, Science operations begin! |
 Oct 12 2020, 04:21 AM
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#166
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 Senior Member  Group: Members Posts: 2086 Joined: 13-February 10 From: Ontario Member No.: 5221  |
I don't understand how you could have a void at the centre of Bennu; where would all the fine material absent from the surface have migrated to? Don't get me wrong, a hollow asteroid would be an amazing discovery, but the paper itself ( https://advances.sciencemag.org/content/6/41/eabc3350 ) does not mention the 'void' quoted in the articles.
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Oct 12 2020, 06:42 AM
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#167
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Senior Member Group: Members Posts: 2517 Joined: 13-September 05 Member No.: 497 |
QUOTE (Explorer1 @ Oct 11 2020, 08:21 PM)  the paper itself does not mention the 'void' quoted in the articles. The article is IMHO an oversimplification (it says "as if" there was a void, not that there's really a void), but the paper does say that the core is underdense. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Oct 12 2020, 07:10 AM
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#168
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Solar System Cartographer Group: Members Posts: 10168 Joined: 5-April 05 From: Canada Member No.: 227 |
"I dream that one day Phil will make a complete atlas of small, non-spherical bodies of the Solar System (asteroids, comets, small moons) photographed so far by space probes"
If people would stop doing things on the Moon and Mars I might have time for that. 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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Oct 12 2020, 07:49 PM
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#169
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Member Group: Members Posts: 436 Joined: 14-December 15 Member No.: 7860 |
QUOTE (mcaplinger @ Oct 12 2020, 08:42 AM) The article is IMHO an oversimplification (it says "as if" there was a void, not that there's really a void), but the paper does say that the core is underdense. Oversimplification can sometimes be the best way to attract people to "boring" science articles (describing reality)...  But in fact, doing so can be risky! As for the loose structure of the interior and the migration of material, we should remember that on Bennu there is very, very little gravity and in these conditions the centrifugal force (as a result of rotation) becomes really important |
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Oct 12 2020, 08:09 PM
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#170
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Member Group: Members Posts: 436 Joined: 14-December 15 Member No.: 7860 |
QUOTE (Phil Stooke @ Oct 12 2020, 09:10 AM) "I dream that one day Phil will make a complete atlas of small, non-spherical bodies of the Solar System (asteroids, comets, small moons) photographed so far by space probes" If people would stop doing things on the Moon and Mars I might have time for that. Phil Well, then we will have to wait a long time - unfortunately  (the hope is that some great solar storm will damage all probes on Mars and the Moon at once )
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Oct 12 2020, 09:37 PM
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#171
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 Member Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 |
QUOTE (Explorer1 @ Oct 12 2020, 05:21 AM) I don't understand how you could have a void at the centre of Bennu; where would all the fine material absent from the surface have migrated to? Don't get me wrong, a hollow asteroid would be an amazing discovery, but the paper itself ( https://advances.sciencemag.org/content/6/41/eabc3350 ) does not mention the 'void' quoted in the articles. I believe that somewhere I found a paper on how the "brazil nut effect" (big pieces jostle to the top) can be reversed under certain conditions of temperature and gravity. So, while we imagine Bennu as a spherical version of a 2 dimensional freeze-thaw "stone circle" it is at least possible that the inverse can happen, with fines preferentially sorting onto the surface. |
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Oct 15 2020, 02:21 PM
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#172
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Member Group: Members Posts: 540 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
NASA will carry a live broadcast of the first sample collection attempt on Tuesday.
LINK: NASA to broadcast collection activities. |
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Oct 16 2020, 01:06 AM
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#173
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 Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
The packing density of a conglomeration of random fragments can be in the ballpark of 0.36.
Then, a region near the center packed at that density would give you the same under-density as if there were a complete void somewhat smaller than that region. Whether or not a world could evolve such that the central region is less packed than the "mantle" is an exercise left to the reader. https://www.pnas.org/content/pnas/early/201...768111.full.pdf |
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Oct 20 2020, 05:41 PM
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#174
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Senior Member Group: Members Posts: 2086 Joined: 13-February 10 From: Ontario Member No.: 5221 |
Livestream of simulated spacecraft events has started, link here:
https://www.asteroidmission.org/livestream/ NASA TV will go live at 5:00 EST. |
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Oct 20 2020, 06:39 PM
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#175
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 Senior Member Group: Members Posts: 4247 Joined: 17-January 05 Member No.: 152 |
That's 5pm EDT, or 21:00 UT, for the live NASA TV coverage.
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Oct 20 2020, 07:27 PM
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#176
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Member Group: Members Posts: 540 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
The OSIRIS REx team is updating their Twitter account fairly often for the current hours leading up to collection. For those wanting to check in with those updates between now and NASA TV going live (and maybe after) you can go HERE.
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Oct 20 2020, 09:30 PM
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#177
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 Merciless Robot Group: Admin Posts: 8784 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Coverage is live on NASA TV.
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Oct 20 2020, 09:43 PM
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#178
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Senior Member Group: Members Posts: 2517 Joined: 13-September 05 Member No.: 497 |
QUOTE (Explorer1 @ Oct 20 2020, 09:41 AM) Livestream seems to have collapsed due to load. http://cristianopi.altervista.org/as/sonde...a_temporea.html is a view from the SPICE predict files but without any spacecraft events [EDIT which seems to have errors of some sort, so ignore, livestream is back.] -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Oct 20 2020, 10:15 PM
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#179
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Senior Member Group: Members Posts: 2086 Joined: 13-February 10 From: Ontario Member No.: 5221 |
TAG completed! Spacecraft going back up!
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Oct 20 2020, 10:16 PM
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#180
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Senior Member Group: Members Posts: 2517 Joined: 13-September 05 Member No.: 497 |
Sampling complete! Now to get the images back and verify sample mass.
-------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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