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Asteroid approach, Science operations begin!
Marcin600
post Jun 9 2020, 08:43 PM
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Today, June 9, a very interesting article appeared in Nature Communications, regarding the issues we recently discussed in this forum thread:

Molaro et al. "In situ evidence of thermally induced rock breakdown on Bennu's surface" (pdf with open access)

It has been summarized on the OSIRIS-REx website: "NASA's OSIRIS-REx Discovers Sunlight Can Crack Rocks on Asteroid Bennu"


Few quotes:

“...This is the first time evidence for this process, called thermal fracturing, has been definitively observed on an object without an atmosphere...”

„ ...[OSIRIS-REx] found evidence of exfoliation, where thermal fracturing likely caused small, thin layers (1 – 10 centimeters) to flake off of boulder surfaces. The spacecraft also produced images of cracks running through boulders in a north-south direction, along the line of stress that would be produced by thermal fracturing on Bennu...”

„...Meteoroid impacts do occur on Bennu and can certainly crack rocks, but they would not cause the even erosion of layers from boulder surfaces that were seen. Also, there’s no sign of impact craters where the exfoliation is occurring...”

“...We don’t have good constraints yet on breakdown rates from thermal fracturing, but we can get them now that we can actually observe it for the first time in situ,” said OSIRIS-REx project scientist Jason Dworkin of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Laboratory measurements on the properties of the samples returned by the spacecraft in 2023 will help us learn more about how this process works...”
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Holder of the Tw...
post Jun 17 2020, 01:49 PM
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NASA has released a mosaic picture of the prime landing site Nightingale.

Here is a LINK to the news release which in turn will provide a link to picture selection.

The full resolution mosaic is 345 PolyCam images stitched together, at a resolution of 4mm, is a 152 MB download and is 14371 X 14488 in size.
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Marcin600
post Jun 19 2020, 05:08 PM
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Another amazingly flat boulder on Bennu, close to Osprey - taken by OSIRIS-REx PolyCam on May 26, from 0.3 km
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palebutdot
post Jul 14 2020, 07:09 AM
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Earth and Moon seen from Asteroid Bennu
https://sbnarchive.psi.edu/pds4/orex/orex.t...ta_raw/orbit_a/
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Holder of the Tw...
post Aug 12 2020, 02:27 PM
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According to the mission's Twitter site, the matchpoint rehearsal appears to have gone okay. They are still downloading data so there is yet to be any formal news release or status update.

Osiris-Rex twitter
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Explorer1
post Aug 12 2020, 10:09 PM
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Video is up!
https://www.youtube.com/watch?v=a1IdyXAwDXQ
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Phil Stooke
post Sep 11 2020, 11:03 PM
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In preparation for the sampling I have updated my Bennu map. This uses a new paper in JGR-Planets to identify more particle ejection sites. With so many I have decided to remove the dates. Also added: dates of the imaging and rehearsal events for the candidate sites.

Phil

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... because the Solar System ain't gonna map itself.

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Phil Stooke
post Sep 19 2020, 11:16 PM
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Here is an interesting abstract from the Apophis workshop coming up in November:

http://www.hou.usra.edu/meetings/apophis2020/pdf/2008.pdf

It's an extended mission for OSIRIS-REx, which would orbit Apophis in 2029. This is just one of several suggestions for Apophis missions at:

https://www.hou.usra.edu/meetings/apophis20...020_program.htm



Phil


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vjkane
post Sep 20 2020, 12:58 AM
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QUOTE (Phil Stooke @ Sep 19 2020, 04:16 PM) *
It's an extended mission for OSIRIS-REx, which would orbit Apophis in 2029. This is just one of several suggestions for Apophis missions at:

As the abstract points out, OSIRIS-REx was designed to explore asteroids like this. I wonder if operations costs for the eight year flight time might be too much.


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Marcin600
post Sep 23 2020, 05:48 AM
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New, interesting results on the OSIRIS-Rex website: OSIRIS-Rex Finds Vesta Meteorites on Asteroid Bennu

"...six boulders (1.5 to 4.3 m) scattered across Bennu’s southern hemisphere and near the equator...[are] almost ten times brighter than their surroundings...
[Spectrum] signature from the boulders [analyzed by OVIRS spectrometer] was characteristic of the mineral pyroxene, similar to what is seen on Vesta and the vestoids..."
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Phil Stooke
post Sep 23 2020, 06:48 AM
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I just couldn't go to bed without adding those locations to the map. Very interesting!

Phil

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marsbug
post Sep 24 2020, 09:06 AM
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That's an awesome map (I do have a soft spot for maps of strange and distant places)!


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Marcin600
post Sep 24 2020, 06:07 PM
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This is undoubtedly the best Bennu map!

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 smile.gif
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Marcin600
post Sep 26 2020, 03:18 AM
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The first attempt of TAG sample collection event is scheduled for October 20
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Marcin600
post Oct 12 2020, 01:44 AM
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Another articles with new, very interesting results discussed on the OSIRIS-REx website

- carbon-bearing, organic material -> bright veins on boulders made of carbonate -> Bennu’s parent asteroid had an extensive hydrothermal system

- Bennu’s “colors” variations -> Nightingale’s regolith has only recently been exposed to the space weathering

- two main types of boulders: 1: dark, rough, weaker and more porous, and 2: bright, smooth, stronger and less porous (host the carbonates) -> formed at different depths in the parent asteroid -> both types are weaker than expected -> dark boulders would not survive the journey through Earth’s atmosphere -> this type of material is not currently represented in meteorite collections

- 3D digital terrain model of Bennu at 20 cm resolution (Laser Altimeter data) -> revealed ridge-like mounds that extend from pole-to-pole; northern and southern hemispheres have different shapes

- gravity field of Bennu determined by tracking the trajectories of the spacecraft and the particles naturally ejected from surface -> interior of Bennu is not uniform -> pockets of higher and lower density material inside; a void at Bennu’s center, within which you could fit a couple of football fields; the bulge at equator is under-dense -> Bennu’s rotation is lofting this material...
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