Asteroid approach, Science operations begin! |
Asteroid approach, Science operations begin! |
Apr 14 2019, 09:03 AM
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#76
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Member Group: Members Posts: 120 Joined: 26-May 15 From: Rome - Italy Member No.: 7482 |
This revolutionizes a bit how I imagined the surface of asteroids forever and how we all imagined it, I think. It does not seem something anomalous or alien but something very common, any valley of terrestrial stones that is often found in the high mountains. I am trying to imagine the men in scale in these photos, exploring among those numerous rocks and I realize that there are so many that it would be difficult to walk there. So many "common" rocks let me think of the remains a part of an already existing and exploded world rather than an agglomeration formed with millions and millions of years. I probably can't conceive.
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Apr 15 2019, 10:17 PM
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#77
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Member Group: Members Posts: 437 Joined: 14-December 15 Member No.: 7860 |
"Benben" - largest boulder on Bennu: https://www.asteroidmission.org/20190307-polycam-benben/
(I found in reliable Wikipedia: "Benben was the mound that arose from the primordial waters Nu upon which the creator deity Atum settled in the creation myth of the Heliopolitan form of ancient Egyptian religion. The Benben stone (also known as a pyramidion) is the top stone of the pyramid. It is also related to the Obelisk." - https://en.wikipedia.org/wiki/Benben And for fun, and for scale - a brave future astronaut exploring this huge rock with pickax |
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Apr 16 2019, 01:29 AM
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#78
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Member Group: Members Posts: 437 Joined: 14-December 15 Member No.: 7860 |
This revolutionizes a bit how I imagined the surface of asteroids forever and how we all imagined it, I think. It does not seem something anomalous or alien but something very common, any valley of terrestrial stones that is often found in the high mountains. I am trying to imagine the men in scale in these photos, exploring among those numerous rocks and I realize that there are so many that it would be difficult to walk there. So many "common" rocks let me think of the remains a part of an already existing and exploded world rather than an agglomeration formed with millions and millions of years. I probably can't conceive. [] "So many "common" rocks let me think of the remains a part of an already existing and exploded world rather than an agglomeration formed with millions and millions of years." In the case of Ryugu, according to this article in Science, one of the models of its origin assumes that it (or rather its parent body) was broken into pieces by catastrophic impact and reaccumulated, at least a couple of times! Maybe the same applies to Bennu (?) |
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Apr 16 2019, 10:36 PM
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#79
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Member Group: Members Posts: 593 Joined: 20-April 05 Member No.: 279 |
I need help here.
I can see a protoplanetary disc containing silicon and oxygen, and I can see these elements combining to make molecules that may later join together to form rock-dust-bunnies, bonded by electrostatic forces. Here on Bennu I'm looking at consolidated rocks, alongside other 'conglomerates' that do not appear, at least at first glance, as particularly rock-like. What is the step from dust to solid rock? Does it imply gravity (there's precious little here), heat from impacts (but, then, what keeps the dust together in such a collision?) How does it potentially occur? Andy |
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Apr 16 2019, 11:26 PM
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#80
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Member Group: Members Posts: 437 Joined: 14-December 15 Member No.: 7860 |
I need help here. I can see a protoplanetary disc containing silicon and oxygen, and I can see these elements combining to make molecules that may later join together to form rock-dust-bunnies, bonded by electrostatic forces. Here on Bennu I'm looking at consolidated rocks, alongside other 'conglomerates' that do not appear, at least at first glance, as particularly rock-like. What is the step from dust to solid rock? Does it imply gravity (there's precious little here), heat from impacts (but, then, what keeps the dust together in such a collision?) How does it potentially occur? Andy Remember that small rocky asteroids like Bennu or Ryugu are not substantially primordial bodies, but formed from the breakdown of much, much larger asteroids. On these larger parent bodies (primordial), gravity was much higher, impact resistance was greater and, at the beginning, there was a lot of heat from the decomposition of short-lived elements, like aluminium (aluminum isotope Al26 |
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Apr 16 2019, 11:34 PM
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#81
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Member Group: Members Posts: 437 Joined: 14-December 15 Member No.: 7860 |
As far as I know, the details of the transition "from dust to rocks" are not well known (?) and it is being investigated (and its vision changes) before our eyes! The only "truly" primordial object we have seen so far is Ultima Thule, but it has a different composition (a lot of "ice"), because it is located (and always was there) far from the Sun.
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Apr 17 2019, 08:44 PM
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#82
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Senior Member Group: Members Posts: 1887 Joined: 20-November 04 From: Iowa Member No.: 110 |
The popular model these days is that in the protoplanetary disk dust grews into pebbles, probably mm sized in the inner solar system. In some parts of the disk these be came concentrated enough by one of a variety of of mechanisms to undergo a gravitational instability which caused clumps of them to collapse into asteroids ~100km in diameter. The consolidated rocks would form in these asteroids and be broken up and scattered in later collisions.
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Apr 18 2019, 01:53 AM
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#83
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
My understanding, via meteorites:
Parent bodies were either differentiated (large enough to have possessed sufficient radiogenic heat to melt) or not. From those that were smaller, we have chondrites, whose solid minerals date back to the first millions of years after the origin of the solar system. Chondrites have iron in abundance along with other stone – a lot like the overall composition of the Earth or Venus if you count the cores and mantles both – but in the chondrites, iron and stone are mixed on a fine level. From larger parent bodies, exemplified near the larger end by Vesta, we have achondrites. Like smaller versions of the Earth and Venus, these were large enough to melt through, and their iron descended into a core, leaving a relatively iron-poor mantle/crust. Meteorites from Vesta therefore have elemental composition approximately like the crusts of Earth or Venus. Bennu sure looks like some interesting geology has taken place, but it is classified as carbonaceous and is thus likely a fragment of a smaller, undifferentiated parent body rather than a larger one. If so, we'll expect to find higher levels of iron when we get those samples. http://meteorites.wustl.edu/metcomp/index_files/image002.gif |
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May 10 2019, 02:05 AM
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#84
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Senior Member Group: Members Posts: 1075 Joined: 21-September 07 From: Québec, Canada Member No.: 3908 |
Looking at the published images of Bennu (link), I noticed that two of them could be stitched together:
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May 14 2019, 11:46 PM
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#85
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Member Group: Members Posts: 437 Joined: 14-December 15 Member No.: 7860 |
North side of Bennu's largest boulder (nicknamed Benben) - rotaded, brightened and with scale bar. In the third picture for scale is Apollo 12 astronaut Pete Conrad with Surveyor 3
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May 15 2019, 12:45 AM
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#86
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Member Group: Members Posts: 437 Joined: 14-December 15 Member No.: 7860 |
And a bit more "free" version of this photo with Apollo 12 astronaut Pete Conrad with Surveyor 3 for scale
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May 15 2019, 08:08 PM
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#87
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Senior Member Group: Members Posts: 2922 Joined: 14-February 06 From: Very close to the Pyrénées Mountains (France) Member No.: 682 |
Why did you choose the shortest men on the Moon?
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May 15 2019, 08:32 PM
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#88
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Member Group: Members Posts: 437 Joined: 14-December 15 Member No.: 7860 |
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Jul 2 2019, 03:01 PM
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#89
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Senior Member Group: Members Posts: 1075 Joined: 21-September 07 From: Québec, Canada Member No.: 3908 |
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Aug 13 2019, 01:23 PM
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#90
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Member Group: Members Posts: 544 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
Four candidate sample sites on Bennu have been selected.
Link to News Release on Candidate Sample Sites for OSIRIS-Rex |
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