Asteroid approach, Science operations begin! |
Asteroid approach, Science operations begin! |
Aug 24 2018, 06:48 PM
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#1
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Member Group: Members Posts: 544 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
NASA update on the OSIRIS-REx mission, includes first picture of the asteroid from the spacecraft.
Begins Operations |
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Apr 14 2020, 11:15 AM
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#2
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Member Group: Members Posts: 120 Joined: 26-May 15 From: Rome - Italy Member No.: 7482 |
For years I have imagined the small meteorites that fall to Earth like small-craterized, black, burnt, melted rocks. Only when I was older did I discover that burnt and melt is given by the heat of the impact with the atmosphere. So I imagine that the small meteorites that fall on Earth and give rise a Fireballs, if we observed them before the impact with our terrestrial atmosphere, are common rocks, very similar to the terrestrial ones, one of the many as seen above the Bennu terrain in this picture (Am I saying well?):
http://www.unmannedspaceflight.com/index.p...st&id=45604 |
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Apr 18 2020, 07:59 PM
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#3
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
So I imagine that the small meteorites that fall on Earth and give rise a Fireballs, if we observed them before the impact with our terrestrial atmosphere, are common rocks, very similar to the terrestrial ones, one of the many as seen above the Bennu terrain in this picture (Am I saying well?) In at least one case, we have the answer, which is the Moon. Although a small fraction of found meteorites have a lunar origin, we know very well that rocks on the surface of the Moon are not burned or melted looking, and often look rather pristine, at least since the moment when they were last broken, shattered, and refused by impacts. The diversity of meteorites is a large topic, and certainly Earth is very different from asteroid parent bodies. Stony achondrites, originating from larger parent bodies, including the Moon, sometimes can look a lot like an Earth rock, which is why stony achondrites are extremely hard to find except in locations where meteorites are easily distinguished from the local landscape, such as Antarctic ice. This is why virtually all lunar and martian meteorites have been found either in African deserts or Antarctica. Chondrites, however, with small, unevolved parent bodies, are pretty easy to tell from Earth rocks, and it would seem like Bennu is composed of the same stuff as carbonaceous chondrites. If so, they may look like Earth rocks from OSIRIS-REx's cameras, but when sliced open will be completely different. It will be nice to get to verify this in 2023! |
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Apr 20 2020, 11:43 AM
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#4
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Member Group: Members Posts: 120 Joined: 26-May 15 From: Rome - Italy Member No.: 7482 |
In at least one case, we have the answer, which is the Moon. Although a small fraction of found meteorites have a lunar origin, we know very well that rocks on the surface of the Moon are not burned or melted looking, and often look rather pristine, at least since the moment when they were last broken, shattered, and refused by impacts. The diversity of meteorites is a large topic, and certainly Earth is very different from asteroid parent bodies. Stony achondrites, originating from larger parent bodies, including the Moon, sometimes can look a lot like an Earth rock, which is why stony achondrites are extremely hard to find except in locations where meteorites are easily distinguished from the local landscape, such as Antarctic ice. This is why virtually all lunar and martian meteorites have been found either in African deserts or Antarctica. Chondrites, however, with small, unevolved parent bodies, are pretty easy to tell from Earth rocks, and it would seem like Bennu is composed of the same stuff as carbonaceous chondrites. If so, they may look like Earth rocks from OSIRIS-REx's cameras, but when sliced open will be completely different. It will be nice to get to verify this in 2023! Many thanks for the reply. Yes, I know that these rocks will be very different internally than the terrestrial ones. I was surprised to see common rocks, chipped, squared as in any terrain on Earth. In fanasia I expected a little more "alien" landscapes, instead I see landscapes very common and familiar to all of us, :-) |
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Apr 20 2020, 06:53 PM
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#5
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Member Group: Members Posts: 437 Joined: 14-December 15 Member No.: 7860 |
... I was surprised to see common rocks, chipped, squared as in any terrain on Earth. In fanasia I expected a little more "alien" landscapes, instead I see landscapes very common and familiar to all of us, :-) This is because the basic laws of physics are the same throughout the Universe. But if you stood on Bennu and kicked these stones you would immediately see the difference - if you found yourself in a cloud of rock fragments flying everywhere (due to microgravity, like here) - such things on Earth are impossible |
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