APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

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APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by APOD Robot » Wed Sep 16, 2020 4:07 am

Image Gravel Ejected from Asteroid Bennu

Explanation: Why does asteroid Bennu eject gravel into space? No one is sure. The discovery, occurring during several episodes by NASA's visiting ORISIS-REx spacecraft, was unexpected. Leading ejection hypotheses include impacts by Sun-orbiting meteoroids, sudden thermal fractures of internal structures, and the sudden release of a water vapor jet. The featured two-image composite shows an ejection event that occurred in early 2019, with sun-reflecting ejecta seen on the right. Data and simulations show that large gravel typically falls right back to the rotating 500-meter asteroid, while smaller rocks skip around the surface, and the smallest rocks completely escape the low gravity of the Earth approaching, diamond-shaped asteroid. Jets and surface ejection events were thought to be predominantly the domain of comets, responsible for their tails, comas, and later meteor showers on Earth. Robotic OSIRIS-REx arrived at 101955 Bennu in late 2018, and is planned to touchdown to collect a surface sample in October 2020. If all goes well, this sample will then be returned to Earth for a detailed analysis during 2023. Bennu was chosen as the destination for OSIRIS-REx in part because its surface shows potential to reveal organic compounds from the early days of our Solar System, compounds that could have been the building blocks for life on Earth.

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Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by bystander » Wed Sep 16, 2020 4:16 am

Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
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Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by LMMdT » Wed Sep 16, 2020 7:04 am

I thought that the cameras in such a machine could resolve up to some-meters-wide objects. Should we conclude that what is shown as a ejection are big rocks? Could gravel-size objetcs (some centimetres) be seen? I would very much appreciate any coment coming from you to clarify this.

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Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by JohnD » Wed Sep 16, 2020 9:30 am

How ironic! Enormous achievement, to design and build a probe that can land, collect and return a sample of Bennu - to find when it gets there that Bennu will willingly throw samples up to the mother probe!

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Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by rstevenson » Wed Sep 16, 2020 10:42 am

LMMdT wrote:
Wed Sep 16, 2020 7:04 am
I thought that the cameras in such a machine could resolve up to some-meters-wide objects. Should we conclude that what is shown as a ejection are big rocks? Could gravel-size objetcs (some centimetres) be seen? I would very much appreciate any coment coming from you to clarify this.
Clicking on the second link in the write up above (“The discovery...”) took me to an article in which I found this statement: “The observed particles ... measured from smaller than an inch up to 4 inches (10 centimeters) in size.” I guess the word “gravel” as used above is to be interpreted loosely. :mrgreen:

Rob

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Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by De58te » Wed Sep 16, 2020 10:55 am

Maybe I can submit another hypothesis for the ejecting gravel. There could be a civilization of tiny reptile or insect people living there in a medieval time period who are are at war with each other and flinging stones by catapults at their enemy on the other side of their world.

Tszabeau

Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by Tszabeau » Wed Sep 16, 2020 11:03 am

Bennu And The Jets. Sorry but... someone had to say it.

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Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by orin stepanek » Wed Sep 16, 2020 12:47 pm

BennuEjecting_OsirisRex_960.jpg
Planetoid almost looks like it is made of soil! Could it be that it may have been ejected into space from a volcanic eruption from some mountain top from another planet? Imagination running wild again! :mrgreen:
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Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by neufer » Wed Sep 16, 2020 1:12 pm

rstevenson wrote:
Wed Sep 16, 2020 10:42 am
LMMdT wrote:
Wed Sep 16, 2020 7:04 am

I thought that the cameras in such a machine could resolve up to some-meters-wide objects. Should we conclude that what is shown as a ejection are big rocks? Could gravel-size objetcs (some centimetres) be seen? I would very much appreciate any coment coming from you to clarify this.
Clicking on the second link in the write up above (“The discovery...”) took me to an article in which I found this statement: “The observed particles ... measured from smaller than an inch up to 4 inches (10 centimeters) in size.” I guess the word “gravel” as used above is to be interpreted loosely. :mrgreen:
Bennu is a carbonaceous asteroid...Ergo: these are charcoal briquettes :!:
https://en.wikipedia.org/wiki/Gravel wrote:
<<Gravel is a loose aggregation of rock fragments. Gravel is classified by particle size range and includes size classes from granule- to boulder-sized fragments. In the Udden-Wentworth scale gravel is categorized into granular gravel (2 to 4 mm) and pebble gravel (4 to 64 mm).>>
Art Neuendorffer

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Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by Chris Peterson » Wed Sep 16, 2020 1:35 pm

LMMdT wrote:
Wed Sep 16, 2020 7:04 am
I thought that the cameras in such a machine could resolve up to some-meters-wide objects. Should we conclude that what is shown as a ejection are big rocks? Could gravel-size objetcs (some centimetres) be seen? I would very much appreciate any coment coming from you to clarify this.
Cameras don't resolve objects of certain physical sizes, but of certain angular sizes. The closer they are to an object, the smaller physical size they can resolve. And this camera is now very close to Bennu, indeed.
Chris

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Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by BDanielMayfield » Wed Sep 16, 2020 1:37 pm

rstevenson wrote:
Wed Sep 16, 2020 10:42 am
LMMdT wrote:
Wed Sep 16, 2020 7:04 am
I thought that the cameras in such a machine could resolve up to some-meters-wide objects. Should we conclude that what is shown as a ejection are big rocks? Could gravel-size objetcs (some centimetres) be seen? I would very much appreciate any coment coming from you to clarify this.
Clicking on the second link in the write up above (“The discovery...”) took me to an article in which I found this statement: “The observed particles ... measured from smaller than an inch up to 4 inches (10 centimeters) in size.” I guess the word “gravel” as used above is to be interpreted loosely. :mrgreen:

Rob
[snark]The IAU needs to make a ruling: Is this really gravel, dwarf gravel or giant gravel? This is a real gravelly question.[/snark]
Just as zero is not equal to infinity, everything coming from nothing is illogical.

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Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by Chris Peterson » Wed Sep 16, 2020 1:46 pm

BDanielMayfield wrote:
Wed Sep 16, 2020 1:37 pm
rstevenson wrote:
Wed Sep 16, 2020 10:42 am
LMMdT wrote:
Wed Sep 16, 2020 7:04 am
I thought that the cameras in such a machine could resolve up to some-meters-wide objects. Should we conclude that what is shown as a ejection are big rocks? Could gravel-size objetcs (some centimetres) be seen? I would very much appreciate any coment coming from you to clarify this.
Clicking on the second link in the write up above (“The discovery...”) took me to an article in which I found this statement: “The observed particles ... measured from smaller than an inch up to 4 inches (10 centimeters) in size.” I guess the word “gravel” as used above is to be interpreted loosely. :mrgreen:

Rob
[snark]The IAU needs to make a ruling: Is this really gravel, dwarf gravel or giant gravel? This is a real gravelly question.[/snark]
Gas gravel, clearly.
Chris

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Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by BDanielMayfield » Wed Sep 16, 2020 1:52 pm

De58te wrote:
Wed Sep 16, 2020 10:55 am
Maybe I can submit another hypothesis for the ejecting gravel. There could be a civilization of tiny reptile or insect people living there in a medieval time period who are are at war with each other and flinging stones by catapults at their enemy on the other side of their world.
Nice. Or maybe they're a little more advanced and they're trying to prevent an alien ship from landing.
Just as zero is not equal to infinity, everything coming from nothing is illogical.

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Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by JohnD » Wed Sep 16, 2020 2:22 pm

Tszabeau wrote:
Wed Sep 16, 2020 11:03 am
Bennu And The Jets. Sorry but... someone had to say it.
Very good.

mike smith

Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by mike smith » Wed Sep 16, 2020 2:45 pm

The chinese beat us there and are mining it.

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Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by Ann » Wed Sep 16, 2020 3:44 pm


So I thought to myself, did the Moon pass in front of a cluster again?

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Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by WWW » Wed Sep 16, 2020 10:25 pm

In an expanded view you can also see a dim halo, (lower right half of Bennu's edge). Is that a camera remnant, a gravel ring, shadows, or a result of multiple exposure layering? Is it possible that some of the dim fragments are actually part of this halo?

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Re: APOD: Gravel Ejected from Asteroid Bennu (2020 Sep 16)

Post by MarkBour » Thu Sep 17, 2020 1:07 am

JohnD wrote:
Wed Sep 16, 2020 9:30 am
How ironic! Enormous achievement, to design and build a probe that can land, collect and return a sample of Bennu - to find when it gets there that Bennu will willingly throw samples up to the mother probe!
Ah, that is pretty rich!
Mark Goldfain