OSIRIS-REx: Asteroid 1999 RQ36 (Bennu)

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Re: OSIRIS-REx: Asteroid 1999 RQ36 (Bennu)

Post by neufer » Thu Dec 06, 2018 2:46 pm


Ann wrote:
Thu Dec 06, 2018 9:46 am

How weird. Bennu is a square asteroid with what appears to be a discarded piece of square or rectangular tarpaulin lying about near its south pole.

I guess the little Bennu-beings wrap the tarpaulin around them when it is time to bed down and go to sleep at night (whenever that is on Bennu), or else the square object might be a door protecting the opening to the Bennu-beings' underground homestead.
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Re: OSIRIS-REx: Asteroid 1999 RQ36 (Bennu)

Post by Ann » Thu Dec 06, 2018 3:44 pm

neufer wrote:
Thu Dec 06, 2018 2:46 pm

Ann wrote:
Thu Dec 06, 2018 9:46 am

How weird. Bennu is a square asteroid with what appears to be a discarded piece of square or rectangular tarpaulin lying about near its south pole.

I guess the little Bennu-beings wrap the tarpaulin around them when it is time to bed down and go to sleep at night (whenever that is on Bennu), or else the square object might be a door protecting the opening to the Bennu-beings' underground homestead.
Munchkin country, eh?

I bet the Munchkin cats live there. They live there because it's blue, and they love blue things.

Click to play embedded YouTube video.
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Planetary Defense: The Bennu Experiment

Post by bystander » Fri Dec 07, 2018 5:35 pm

Planetary Defense: The Bennu Experiment
NASA | JPL-Caltech | OSIRIS-REx | 2018 Dec 06

On Dec. 3, after traveling billions of kilometers from Earth, NASA's OSIRIS-REx spacecraft reached its target, Bennu, and kicked off a nearly two-year, up-close investigation of the asteroid. It will inspect nearly every square inch of this ancient clump of rubble left over from the formation of our solar system. Ultimately, the spacecraft will pick up a sample of pebbles and dust from Bennu's surface and deliver it to Earth in 2023.

Generations of planetary scientists will get to study pieces of the primitive materials that formed our cosmic neighborhood and to better understand the role asteroids may have played in delivering life-forming compounds to planets and moons.

But it's not just history that the mission to Bennu will help uncover. Scientists studying the rock through OSIRIS-REx's instruments in space will also shape our future. As they collect the most detailed information yet about the forces that move asteroids, experts from NASA's Planetary Defense Coordination Office, who are responsible for detecting potentially hazardous asteroids, will improve their predictions of which ones could be on a crash-course with our planet. ...
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OSIRIS-REx Discovers Water on Bennu

Post by bystander » Tue Dec 11, 2018 4:12 pm

Newly Arrived OSIRIS-REx Already Discovers Water on Asteroid
NASA | Goddard | OSIRIS-REx | 2018 Dec 10
Recently analyzed data from NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) mission has revealed water locked inside the clays that make up its scientific target, the asteroid Bennu.

During the mission’s approach phase, between mid-August and early December, the spacecraft traveled 1.4 million miles (2.2 million km) on its journey from Earth to arrive at a location 12 miles (19 km) from Bennu on Dec. 3. During this time, the science team on Earth aimed three of the spacecraft’s instruments towards Bennu and began making the mission’s first scientific observations of the asteroid. OSIRIS-REx is NASA’s first asteroid sample return mission.

Data obtained from the spacecraft’s two spectrometers, the OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) and the OSIRIS-REx Thermal Emission Spectrometer (OTES), reveal the presence of molecules that contain oxygen and hydrogen atoms bonded together, known as “hydroxyls.” The team suspects that these hydroxyl groups exist globally across the asteroid in water-bearing clay minerals, meaning that at some point, Bennu’s rocky material interacted with water. While Bennu itself is too small to have ever hosted liquid water, the finding does indicate that liquid water was present at some time on Bennu’s parent body, a much larger asteroid. ...

Additionally, data obtained from the OSIRIS-REx Camera Suite (OCAMS) corroborate ground-based telescopic observations of Bennu and confirm the original model developed in 2013 by OSIRIS-REx Science Team Chief Michael Nolan and collaborators. That model closely predicted the asteroid’s actual shape, with Bennu’s diameter, rotation rate, inclination, and overall shape presented almost exactly as projected. ...

UA-Led OSIRIS-REx Discovers Water on Asteroid Bennu
University of Arizona | 2018 Dec 10

Observations made by the spacecraft during its approach of Bennu reveal that that the asteroid interacted with water in its early history and is an excellent specimen for the mission, which is slated to return a sample of surface material to Earth in 2023. ...

ASU Instrument on NASA Probe Finds Hydrated Minerals on Asteroid Bennu
Arizona State University | School of Earth and Space Exploration | 2018 Dec 10

An ASU spectrometer on NASA’s OSIRIS-REx spacecraft has found strong spectral evidence that the asteroid’s rocks have undergone interactions with water at some point in their history. ...

First Images from OSIRIS-REx Have Scientists Buzzing with Excitement
University of Central Florida | 2018 Dec 10
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Re: OSIRIS-REx Discovers Water on Bennu

Post by neufer » Tue Dec 11, 2018 6:09 pm

Click to play embedded YouTube video.
bystander wrote:
Tue Dec 11, 2018 4:12 pm

UA-Led OSIRIS-REx Discovers Water on Asteroid Bennu
University of Arizona | 2018 Dec 10
Observations made by the spacecraft during its approach of Bennu reveal that that the asteroid interacted with water in its early history and is an excellent specimen for the mission, which is slated to return a sample of surface material to Earth in 2023. ...
:arrow: First Images from OSIRIS-REx Have Scientists Buzzing with Excitement University of Central Florida | 2018 Dec 10
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OSIRIS-REx Enters Close Orbit Around Bennu

Post by bystander » Tue Jan 01, 2019 8:07 pm

OSIRIS-REx Enters Close Orbit Around Bennu
NASA | University of Arizona | OSIRIS-REx | 2018 Dec 31
Click to play embedded YouTube video.

At 2:43 p.m. EST on December 31, while many on Earth prepared to welcome the New Year, NASA’s OSIRIS-REx spacecraft, 70 million miles (110 million kilometers) away, carried out a single, eight-second burn of its thrusters – and broke a space exploration record. The spacecraft entered into orbit around the asteroid Bennu, and made Bennu the smallest object ever to be orbited by a spacecraft. ...

Inching around the asteroid at a snail’s pace, OSIRIS-REx’s first orbit marks a leap for humankind. Never before has a spacecraft from Earth circled so close to such a small space object – one with barely enough gravity to keep a vehicle in a stable orbit.

Now, the spacecraft will circle Bennu about a mile (1.75 kilometers) from its center, closer than any other spacecraft has come to its celestial object of study. (Previously the closest orbit of a planetary body was in May 2016, when the Rosetta spacecraft orbited about four miles (seven kilometers) from the center of the comet 67P/Churyumov-Gerasimenko.) The comfortable distance is necessary to keep the spacecraft locked to Bennu, which has a gravity force only 5-millionths as strong as Earth’s. The spacecraft is scheduled to orbit Bennu through mid-February at a leisurely 62 hours per orbit.

Now that the OSIRIS-REx spacecraft is closer to Bennu, physical details about the asteroid will leap into sharper focus, and the spacecraft’s tour of this rubble pile of primordial debris will become increasingly detailed and focused. ...
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Re: OSIRIS-REx Enters Close Orbit Around Bennu

Post by neufer » Tue Jan 01, 2019 10:02 pm

bystander wrote:
Tue Jan 01, 2019 8:07 pm
OSIRIS-REx Enters Close Orbit Around Bennu
NASA | University of Arizona | OSIRIS-REx | 2018 Dec 31
Inching around the asteroid at a snail’s pace, OSIRIS-REx’s first orbit marks a leap for humankind. Now, the spacecraft will circle Bennu about a mile from its center, closer than any other spacecraft has come to its celestial object of study. The spacecraft is scheduled to orbit Bennu through mid-February at a leisurely 62 hours per orbit.
  • 2π miles per 62 hours = 0.1 mph is more like sand star pace:
https://10mosttoday.com/10-slowest-animals-in-the-world/ wrote:
<<It’s incredible, but yes – some starfish species move faster than sloths and snails! There are about 1,500 species of starfish, and most of them cannot move quickly. The leather star moves at a rate of just 15 cm a minute. But the sand star can travel at a whooping speed of 2.8 meters per minute. That’s about 0.1 mph.>>
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GSFC: OSIRIS-REx Reveals Asteroid Bennu Has Big Surprises

Post by bystander » Wed Mar 20, 2019 4:01 pm

OSIRIS-REx Reveals Asteroid Bennu Has Big Surprises
NASA | Goddard Space Flight Center | 2019 Mar 19
A NASA spacecraft that will return a sample of a near-Earth asteroid named Bennu to Earth in 2023 made the first-ever close-up observations of particle plumes erupting from an asteroid’s surface. Bennu also revealed itself to be more rugged than expected, challenging the mission team to alter its flight and sample collection plans, due to the rough terrain.

Bennu is the target of NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) mission, which began orbiting the asteroid on Dec. 31. Bennu, which is only slightly wider than the height of the Empire State Building, may contain unaltered material from the very beginning of our solar system. ...

Shortly after the discovery of the particle plumes on Jan. 6, the mission science team increased the frequency of observations, and subsequently detected additional particle plumes during the following two months. Although many of the particles were ejected clear of Bennu, the team tracked some particles that orbited Bennu as satellites before returning to the asteroid’s surface.

The OSIRIS-REx team initially spotted the particle plumes in images while the spacecraft was orbiting Bennu at a distance of about one mile (1.61 kilometers). Following a safety assessment, the mission team concluded the particles did not pose a risk to the spacecraft. The team continues to analyze the particle plumes and their possible causes. ...

The OSIRIS-REx team also didn’t anticipate the number and size of boulders on Bennu’s surface. From Earth-based observations, the team expected a generally smooth surface with a few large boulders. Instead, it discovered Bennu’s entire surface is rough and dense with boulders.

The higher-than-expected density of boulders means that the mission’s plans for sample collection, also known as Touch-and-Go (TAG), need to be adjusted. The original mission design was based on a sample site that is hazard-free, with an 82-foot (25-meter) radius. However, because of the unexpectedly rugged terrain, the team hasn’t been able to identify a site of that size on Bennu. Instead, it has begun to identify candidate sites that are much smaller in radius.

The smaller sample site footprint and the greater number of boulders will demand more accurate performance from the spacecraft during its descent to the surface than originally planned. The mission team is developing an updated approach, called Bullseye TAG, to accurately target smaller sample sites. ...

The OSIRIS-REx science team has made many other discoveries about Bennu in the three months since the spacecraft arrived at the asteroid, some of which were presented Tuesday at the 50th Lunar and Planetary Conference in Houston and in a special collection of papers issued by the journal Nature. ...
Team Identifies Water-Bearing Minerals on Asteroid Bennu
Southwest Research Institute | 2019 Mar 19

A Southwest Research Institute-led team discovered evidence of abundant water-bearing minerals on the surface of the near-Earth asteroid (101955) Bennu. Using early spectral data from NASA’s OSIRIS-REx spacecraft orbiting the asteroid, the team identified infrared properties similar to those in a type of meteorite called carbonaceous chondrites. ...
Surprisingly Old Surface Discovered on Near-Earth Asteroid Bennu
Southwest Research Institute | 2019 Mar 19

A Southwest Research Institute-led team has discovered that the surface geology on asteroid Bennu is older than expected. Early observations of the near-Earth asteroid (NEA) by NASA’s OSIRIS-REx mission indicate a surface that is between 100 million and 1 billion years old. ...
OSIRIS-REx Images Allow Closer Look at Boulder Breakup on Bennu
Planetary Science Institute | 2019 Mar 19

High-resolutions images of asteroid Bennu from NASA’s OSIRIS-REx spacecraft offer scientists the opportunity to analyze the processes that break down boulders on the surfaces of airless bodies ...
OSIRIS-REx Spies on the Weird, Wild Gravity of an Asteroid
University of Colorado | 2019 Mar 19

Research led by CU Boulder is revealing the Alice in Wonderland-like physics that govern gravity near the surface of the asteroid Bennu. ...
OSIRIS-REx Spacecraft Studies Asteroid Bennu Up Close
University of Arizona | 2019 Mar 19

When NASA's OSIRIS-REx spacecraft arrived at its destination, asteroid Bennu, on Dec. 3, it found a tiny world that in many respects looks like what the mission team had expected based on ground-based observations, but holds quite a few surprises, too. ...
Bennu spits plumes of dust into space
Science News | 2019 Mar 19

Like the “Peanuts” character Pigpen, the near-Earth asteroid Bennu moves around in a cloud of its own dust. ...

The unexpected surface of asteroid (101955) Bennu ~ OSIRIS-REx Team, D. S. Lauretta et al Properties of rubble-pile asteroid (101955) Bennu from OSIRIS-REx
imaging and thermal analysis
~ OSIRIS-REx Team, D. N. DellaGiustina et al Shape of (101955) Bennu indicative of a rubble pile with internal stiffness ~ OSIRIS-REx Team, O. S. Barnouin et al Craters, boulders and regolith of (101955) Bennu indicative of
an old and dynamic surface
~ OSIRIS-REx Team, K. J. Walsh et al Evidence for widespread hydrated minerals on asteroid (101955) Bennu ~ OSIRIS-REx Team, V. E. Hamilton et al The operational environment and rotational acceleration of asteroid (101955)
Bennu from OSIRIS-REx observations
~ OSIRIS-REx Team, C. W. Hergenrother et al The dynamic geophysical environment of (101955) Bennu based on
OSIRIS-REx measurements
~ OSIRIS-REx Team, D. J. Scheeres et al
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Final Four Site Candidates for Asteroid Sample Return

Post by bystander » Tue Aug 13, 2019 3:39 pm

NASA Selects Final Four Site Candidates for Asteroid Sample Return
NASA | GSFC | OSIRIS-REx | 2019 Aug 12
Click to play embedded YouTube video.
Asteroid Bennu Sample Site Finalists ~ Credit: NASA/GSFC/Kel Elkins
After months grappling with the rugged reality of asteroid Bennu’s surface, the team leading NASA’s first asteroid sample return mission has selected four potential sites for the Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft to “tag” its cosmic dance partner.

Since its arrival in December 2018, the OSIRIS-REx spacecraft has mapped the entire asteroid in order to identify the safest and most accessible spots for the spacecraft to collect a sample. These four sites now will be studied in further detail in order to select the final two sites – a primary and backup – in December.

The team originally had planned to choose the final two sites by this point in the mission. Initial analysis of Earth-based observations suggested the asteroid’s surface likely contains large “ponds” of fine-grain material. The spacecraft’s earliest images, however, revealed Bennu has an especially rocky terrain. Since then, the asteroid’s boulder-filled topography has created a challenge for the team to identify safe areas containing sampleable material, which must be fine enough – less than 1 inch (2.5 cm) diameter – for the spacecraft’s sampling mechanism to ingest it. ...
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Explaining Bennu’s Mysterious Particle Events

Post by bystander » Sun Dec 15, 2019 11:54 pm

Explaining Bennu’s Mysterious Particle Events
NASA | GSFC | JPL-Caltech | University of Arizona | OSIRIS-REx | 2019 Dec 05

NASA's OSIRIS-REx science team has identified three possible explanations for the particles that asteroid Bennu is tossing into space.

Shortly after NASA’s OSIRIS-REx spacecraft arrived at asteroid Bennu, an unexpected discovery by the mission’s science team revealed that the asteroid could be active, or consistently discharging particles into space. The ongoing examination of Bennu and the sample of it that will eventually be returned to Earth, could potentially shed light on why this intriguing phenomenon is occurring.

The OSIRIS-REx team first observed a particle ejection event in images captured by the spacecraft’s navigation cameras taken on Jan. 6, just a week after the spacecraft entered its first orbit around Bennu. At first glance, the particles appeared to be stars behind the asteroid, but on closer examination, the team realized that the asteroid was ejecting material from its surface. After concluding that these particles did not compromise the spacecraft’s safety, the mission began dedicated observations in order to fully document the activity.

“Among Bennu’s many surprises, the particle ejections sparked our curiosity, and we’ve spent the last several months investigating this mystery,” said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona. “This is a great opportunity to expand our knowledge of how asteroids behave.”

After studying the results of the observations, the mission team released their findings in a Science paper published Dec. 6. The team observed the three largest particle ejection events on Jan. 6 and 19, and Feb. 11, and concluded that the events originated from different locations on Bennu’s surface. The first event originated in the southern hemisphere, and the second and third events occurred near the equator. All three events took place in the late afternoon on Bennu. ...

OSIRIS-REx Team Offers Insight into Asteroid Bennu Activity
University of Central Florida | 2019 Dec 06

Close-up View of an Active Asteroid
Science Perspective | 2019 Dec 06

Episodes of Particle Ejection from the Surface of the Active Asteroid (101955) Bennu ~ D. S. Lauretta et al
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NASA Selects Site for Asteroid Sample Collection

Post by bystander » Mon Dec 16, 2019 12:06 am

X Marks the Spot: NASA Selects Site for Asteroid Sample Collection
NASA | GSFC | OSIRIS-REx | 2019 Dec 12
nightingale_0.jpg
This image shows sample site Nightingale, OSIRIS-REx’s primary sample collection site
on asteroid Bennu. The image is overlaid with a graphic of the OSIRIS-REx spacecraft
to illustrate the scale of the site. Credits: NASA/Goddard/University of Arizona

After a year scoping out asteroid Bennu’s boulder-scattered surface, the team leading NASA’s first asteroid sample return mission has officially selected a sample collection site.

The Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-Rex) mission team concluded a site designated “Nightingale” – located in a crater high in Bennu’s northern hemisphere – is the best spot for the OSIRIS-REx spacecraft to snag its sample.

The OSIRIS-REx team spent the past several months evaluating close-range data from four candidate sites in order to identify the best option for the sample collection. The candidate sites – dubbed Sandpiper, Osprey, Kingfisher, and Nightingale – were chosen for investigation because, of all the potential sampling regions on Bennu, these areas pose the fewest hazards to the spacecraft’s safety while still providing the opportunity for great samples to be gathered.

“After thoroughly evaluating all four candidate sites, we made our final decision based on which site has the greatest amount of fine-grained material and how easily the spacecraft can access that material while keeping the spacecraft safe,” said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona in Tucson. “Of the four candidates, site Nightingale best meets these criteria and, ultimately, best ensures mission success.” ...

OSIRIS REx Target on Asteroid Bennu Revealed
University of Central Florida | 2019 Dec 12
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IAU: First Official Names Given to Features on Asteroid Bennu

Post by bystander » Mon Mar 09, 2020 6:58 pm

First Official Names Given to Features on Asteroid Bennu
International Astronomical Union | 2020 Mar 07
12 features on Asteroid Bennu, the subject of NASA’s first mission to bring an asteroid sample back to Earth, have been given official names. Bennu’s own name was inspired by an ancient Egyptian deity, depicted as a bird, that was associated with the Sun, creation and rebirth. In keeping with this theme, the features have been given names related to mythological birds and bird-like creatures.

Asteroid Bennu’s most prominent boulder, a rock chunk jutting out 21.7 metres from the asteroid’s southern hemisphere — so large that it was initially detected from Earth — has been officially designated Benben Saxum, after the primordial hill that first arose from the dark waters in an ancient Egyptian creation myth.

Benben Saxum and 11 other features are the first on the roughly 500 metre-wide asteroid to receive official Bennu feature names approved by the International Astronomical Union (IAU), the internationally recognised authority for naming celestial bodies and their surface features. The accepted names were proposed by NASA’s OSIRIS-REx team members, who have been mapping the asteroid in detail over the last year. The OSIRIS-REx spacecraft is currently orbiting the asteroid and is scheduled to collect a sample from Bennu’s surface this summer. ...
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Arizona/GSFC: One Step Closer to Touching Asteroid Bennu

Post by bystander » Thu Apr 16, 2020 7:18 pm

One Step Closer to Touching Asteroid Bennu
University of Arizona | NASA | GSFC | OSIRIS-REx | 2020 Apr 15
checkpoint_beauty_shot-01[1].png
Artist’s concept shows the trajectory and configuration of NASA’s OSIRIS-REx
spacecraft during Checkpoint rehearsal, which is the first time the mission
practiced the initial steps for collecting a sample from asteroid Bennu.
Credits: NASA/Goddard/University of Arizona

After the successful completion of its “Checkpoint” rehearsal, NASA’s first asteroid-sampling spacecraft is one step closer to touching down on asteroid Bennu. Yesterday, NASA’s OSIRIS-REx spacecraft performed the first practice run of its sample collection sequence, reaching an approximate altitude of 246 feet (75 meters) over site Nightingale before executing a back-away burn from the asteroid. Nightingale, OSIRIS-REx’s primary sample collection site, is located within a crater in Bennu’s northern hemisphere.

The four-hour Checkpoint rehearsal took the spacecraft through the first two of the sampling sequence’s four maneuvers: the orbit departure burn and the Checkpoint burn. Checkpoint is so named because it is the location where the spacecraft autonomously checks its position and velocity before adjusting its trajectory down toward the location of the event’s third maneuver.

Four hours after departing its 0.6-mile (1-km) safe-home orbit, the spacecraft performed the Checkpoint maneuver at an approximate altitude of 410 feet (125 meters) above Bennu’s surface. From there, the spacecraft continued to descend for another nine minutes on a trajectory toward – but not reaching – the location of the sampling event’s third maneuver, the “Matchpoint” burn. Upon reaching an altitude of approximately 246 ft (75 m) – the closest the spacecraft has ever been to Bennu – OSIRIS-REx performed a back-away burn to complete the rehearsal.

During the rehearsal, the spacecraft successfully deployed its sampling arm, the Touch-And-Go Sample Acquisition Mechanism (TAGSAM), from its folded, parked position out to the sample collection configuration. Additionally, some of the spacecraft’s instruments collected science and navigation images and made spectrometry observations of the sample site, as will occur during the sample collection event.

This first rehearsal provided the mission team with practice navigating the spacecraft through both the orbit departure and Checkpoint maneuvers and with an opportunity to verify that the spacecraft’s imaging, navigation and ranging systems operated as expected during the first part of the descent sequence. Checkpoint rehearsal also gave the team confirmation that OSIRIS-REx’s Natural Feature Tracking (NFT) guidance system accurately estimated the spacecraft’s position and speed relative to Bennu as it descended toward the surface. ...
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Arizona/GSFC: OSIRIS-REx Ready for Touchdown on Asteroid Bennu

Post by bystander » Sat May 23, 2020 7:29 pm

OSIRIS-REx Ready for Touchdown on Asteroid Bennu
University of Arizona | NASA | GSFC | OSIRIS-REx | 2020 May 20
NASA’s first asteroid sample return mission is officially prepared for its long-awaited touchdown on asteroid Bennu’s surface. The Origins, Spectral Interpretation, Resource Identification and Security – Regolith Explorer (OSIRIS-REx) mission has targeted Oct. 20 for its first sample collection attempt.

“The OSIRIS-REx mission has been demonstrating the very essence of exploration by persevering through unexpected challenges,” said Thomas Zurbuchen, NASA’s associate administrator for science. “That spirit has led them to the cusp of the prize we all are waiting for – securing a sample of an asteroid to bring home to Earth, and I’m very excited to follow them through the home stretch.”

From discovering Bennu’s surprisingly rugged and active surface, to entering the closest-ever orbit around a planetary body, OSIRIS-REx has overcome several challenges since arriving at the asteroid in December 2018. Last month, the mission brought the spacecraft 213 ft (65 m) from the asteroid’s surface during its first sample collection rehearsal — successfully completing a practice run of the activities leading up to the sampling event. ...

OSIRIS-REx Asteroid Sample Collection Set for Oct. 20
University of Arizona | 2020 May 21
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Sunlight Can Crack Rocks on Bennu

Post by bystander » Wed Jun 10, 2020 9:27 pm

OSIRIS-REx Discovers Sunlight Can Crack Rocks on Asteroid Bennu
NASA | GSFC | OSIRIS-REx | 2020 Jun 09
Asteroids don’t just sit there doing nothing as they orbit the Sun. They get bombarded by meteoroids, blasted by space radiation, and now, for the first time, scientists are seeing evidence that even a little sunshine can wear them down.

Rocks on asteroid Bennu appear to be cracking as sunlight heats them up during the day and they cool down at night, according to images from NASA’s OSIRIS-REx (Origins Spectral Interpretation Resource Identification Security - Regolith Explorer) spacecraft.

“This is the first time evidence for this process, called thermal fracturing, has been definitively observed on an object without an atmosphere,” said Jamie Molaro of the Planetary Science Institute, Tucson, Arizona ... “It is one piece of a puzzle that tells us what the surface used to be like, and what it will be like millions of years from now.”

“Like any weathering process, thermal fracturing causes the evolution of boulders and planetary surfaces over time - from changing the shape and size of individual boulders, to producing pebbles or fine-grained regolith, to breaking down crater walls,” said OSIRIS-REx principal investigator Dante Lauretta of the University of Arizona, Tucson. “How quickly this occurs relative to other weathering processes tells us how and how quickly the surface has changed.” ...

OSIRIS-REx Finds Heat, Cold Fracturing Rocks on Asteroid Bennu
Planetary Science Institute | 2020 Jun 09

In Situ Evidence of Thermally Induced Rock Breakdown Widespread on Bennu’s Surface ~ J. L. Molaro et al
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Re: Sunlight Can Crack Rocks on Bennu

Post by BDanielMayfield » Wed Jun 10, 2020 11:41 pm

bystander wrote:
Wed Jun 10, 2020 9:27 pm
OSIRIS-REx Discovers Sunlight Can Crack Rocks on Asteroid Bennu
NASA | GSFC | OSIRIS-REx | 2020 Jun 09
Asteroids don’t just sit there doing nothing as they orbit the Sun. They get bombarded by meteoroids, blasted by space radiation, and now, for the first time, scientists are seeing evidence that even a little sunshine can wear them down.

Rocks on asteroid Bennu appear to be cracking as sunlight heats them up during the day and they cool down at night, according to images from NASA’s OSIRIS-REx (Origins Spectral Interpretation Resource Identification Security - Regolith Explorer) spacecraft.

“This is the first time evidence for this process, called thermal fracturing, has been definitively observed on an object without an atmosphere,” said Jamie Molaro of the Planetary Science Institute, Tucson, Arizona ... “It is one piece of a puzzle that tells us what the surface used to be like, and what it will be like millions of years from now.”

“Like any weathering process, thermal fracturing causes the evolution of boulders and planetary surfaces over time - from changing the shape and size of individual boulders, to producing pebbles or fine-grained regolith, to breaking down crater walls,” said OSIRIS-REx principal investigator Dante Lauretta of the University of Arizona, Tucson. “How quickly this occurs relative to other weathering processes tells us how and how quickly the surface has changed.” ...

OSIRIS-REx Finds Heat, Cold Fracturing Rocks on Asteroid Bennu
Planetary Science Institute | 2020 Jun 09

In Situ Evidence of Thermally Induced Rock Breakdown Widespread on Bennu’s Surface ~ J. L. Molaro et al
As thermal cracks happen to rocks, concrete sidewalks, etc. on the Earth's surface where temperature extremes aren't nearly as bad as in the vacuum of space it seems like this would have been expected and noticed long before now. Didn't they find thermally broken rocks on the Moon back when men where men and went there? :|
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Re: Sunlight Can Crack Rocks on Bennu

Post by neufer » Thu Jun 11, 2020 2:03 am

BDanielMayfield wrote:
Wed Jun 10, 2020 11:41 pm

As thermal cracks happen to rocks, concrete sidewalks, etc. on the Earth's surface where temperature extremes aren't nearly as bad as in the vacuum of space it seems like this would have been expected and noticed long before now. Didn't they find thermally broken rocks on the Moon back when men where men and went there? :|
Cracks that happen to rocks on the Earth's surface are often due to water seepage that freezes % expands.

Cracks that happen to concrete sidewalks are often due to tree roots or underlying moisture-induced clay expansion/contractions.
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Re: Sunlight Can Crack Rocks on Bennu

Post by BDanielMayfield » Thu Jun 11, 2020 2:51 am

neufer wrote:
Thu Jun 11, 2020 2:03 am
BDanielMayfield wrote:
Wed Jun 10, 2020 11:41 pm

As thermal cracks happen to rocks, concrete sidewalks, etc. on the Earth's surface where temperature extremes aren't nearly as bad as in the vacuum of space it seems like this would have been expected and noticed long before now. Didn't they find thermally broken rocks on the Moon back when men where men and went there? :|
Cracks that happen to rocks on the Earth's surface are often due to water seepage that freezes % expands.

Cracks that happen to concrete sidewalks are often due to tree roots or underlying moisture-induced clay expansion/contractions.
I agree that those are frequently the causes of such cracks on Earth. But thermal expansion cause them too. To avoid them is why expansion joints are used in concrete sidewalks and roadways.
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JPL: Why Is Asteroid Bennu Ejecting Particles into Space?

Post by bystander » Thu Sep 10, 2020 9:03 pm

Why Is Asteroid Bennu Ejecting Particles into Space?
NASA | JPL-Caltech | OSIRIS-REx | 2020 Sep 09

The asteroid, which is being studied by NASA's OSIRIS-REx, shows some surprising activity on its surface, and scientists are beginning to understand what might be causing it.

When NASA's OSIRIS-REx spacecraft arrived at asteroid (101955) Bennu, mission scientists knew that their spacecraft was orbiting something special. Not only was the boulder-strewn asteroid shaped like a rough diamond, its surface was crackling with activity, shedding small pieces of rock into space. Now, after more than a year and a half up close with Bennu, they're starting to better understand these dynamic particle-ejection events.

A collection of studies in a special edition of the Journal of Geophysical Research: Planets homes in on the asteroid and these enigmatic particles. The studies provide a detailed look at how these particles act when in space, possible clues as to how they're ejected, and even how their trajectories can be used to approximate Bennu's weak gravitational field. ...

Study Indicates Sand-Sized Meteroids are Peppering Asteroid Bennu
Southwest Research Institute | 2020 Sep 09

Exploration of the Activity of Asteroid (101955) Bennu ~ C. W. Hergenrother et al Autonomous Detection of Particles and Tracks in Optical Images ~ Andrew J. Liounis et al Reconstruction of Bennu Particle Events from Sparse Data ~ John Y. Pelgrift et al Initial Orbit Determination and Event Reconstruction from
Estimation of Particle Trajectories about (101955) Bennu
~ J. M. Leonard et al Particle Ejection Contributions to the Rotational Acceleration
and Orbit Evolution of Asteroid (101955) Bennu
~ D. J. Scheeres et al Dynamical Evolution of Simulated Particles Ejected from Asteroid Bennu ~ Jay W. McMahon et al Meteoroid Impacts as a Source of Bennu's Particle Ejection Events ~ W. F. Bottke et al Implications for Ice Stability and Particle Ejection from High‐
Resolution Temperature Modeling of Asteroid (101955) Bennu
~ B. Rozitis et al Thermal Fatigue as a Driving Mechanism for Activity on Asteroid Bennu ~ J. L. Molaro et al Trajectory Estimation for Particles Observed in the Vicinity of (101955) Bennu ~ S. R. Chesley et al
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SwRI: Scientists Study Rugged Surface of Bennu

Post by bystander » Mon Oct 12, 2020 8:13 pm

Scientists Study Rugged Surface of Near-Earth Asteroid Bennu
Southwest Research Institute | 2020 Oct 08
As the days count down to NASA’s OSIRIS-REx spacecraft’s Touch-And-Go asteroid sample collection attempt, Southwest Research Institute scientists have helped determine what the spacecraft can expect to return from the near-Earth asteroid Bennu’s surface. Three papers published online by Science on Oct. 8 discuss the color, reflectivity, age, composition, origin and distribution of materials that make up the asteroid’s rough surface.

On October 20, the spacecraft will descend to the asteroid’s boulder-strewn surface, touch the ground with its robotic arm for a few seconds and collect a sample of rocks and dust – marking the first time NASA has grabbed pieces of an asteroid for return to Earth. SwRI scientists played a role in the selection of the sample sites. The first attempt will be made at Nightingale, a rocky area 66 feet in diameter in Bennu’s northern hemisphere. If this historic attempt is unsuccessful, the spacecraft will try again at a secondary site.

Since the spacecraft arrived at Bennu in 2018, scientists have been characterizing the asteroid's composition and comparing it to other asteroids and meteorites. The mission discovered carbon-bearing compounds on Bennu’s surface, a first for a near-Earth asteroid, as well as minerals containing or formed by water. Scientists also studied the distribution of these materials, globally and at the sample sites. ...

Variations in Color and Reflectance on the Surface of Asteroid (101955) Bennu ~ D. N. DellaGiustina et al Bright Carbonate Veins on Asteroid (101955) Bennu: Implications for Aqueous Alteration History ~ H. H. Kaplan et al Widespread Distribution of Carbon-Bearing Materials on Near-Earth Asteroid (101955) Bennu ~ Amy Simon et al
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Arizona: Why Scooping an Asteroid Sample Is Harder Than It Looks

Post by bystander » Fri Oct 16, 2020 3:32 pm

Why Scooping an Asteroid Sample Is Harder Than It Looks
University of Arizona | 2020 Oct 15
Click to play embedded YouTube video.
NASA’s Asteroid Heist: The Challenges of TAG ~ Credit: NASA/GSFC/USRA
The sampler head of the OSIRIS-REx spacecraft works not unlike a reverse vacuum cleaner,
designed to collect loose material from the surface of asteroid Bennu on Oct. 20.

Here's what will happen on Oct. 20, when NASA's OSIRIS-REx spacecraft will descend to asteroid Bennu and pick up a sample of pristine material left over from the formation of our solar system.

When NASA's OSIRIS-REx spacecraft descends toward the surface of Bennu on Oct. 20, it will be the first time that a U.S.-led mission attempts to pick up a sample of pristine material from an asteroid. Bennu is likely an extraterrestrial accumulation of the original leftovers from the formation of our solar system. ...

Once the spacecraft has set off on the descent to its target, it will rely on what the mission team calls a "hazard map" – a detailed representation of areas within the sample site that may present a risk to the spacecraft due to the presence of large rocks or uneven terrain.

Just prior to touching the surface, the spacecraft will compare images from one of its cameras with the hazard map stored in the spacecraft's memory. If the descent path would result in the spacecraft touching down in a potentially unsafe spot, the system would automatically trigger the spacecraft to back away, a scenario that has a probability of less than 6% based on simulations.

If everything goes well, the spacecraft will extend its Touch-and-Go Sample Acquisition Mechanism, or TAGSAM, which is suspended at the tip of an 11-feet-long arm. Reminiscent of an air filter used in an older car, it is designed to collect fine grained material, but is capable of ingesting material up to about three quarters of an inch. ...
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NASA: OSIRIS-REx Successfully Touches Asteroid

Post by bystander » Wed Oct 21, 2020 4:07 pm

OSIRIS-REx Successfully Touches Asteroid
NASA | GSFC | OSIRIS-REx | 2020 Oct 20

NASA’s Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) spacecraft unfurled its robotic arm Tuesday, and in a first for the agency, briefly touched an asteroid to collect dust and pebbles from the surface for delivery to Earth in 2023. ...

Click to play embedded YouTube video.
OSIRIS-REx Touch and Go (TAG) and Sample Stow Sequence ~ Credit: NASA/GSFC
At 1:50 p.m. EDT, OSIRIS-REx fired its thrusters to nudge itself out of orbit around Bennu. It extended the shoulder, then elbow, then wrist of its 11-foot (3.35-meter) sampling arm, known as the Touch-And-Go Sample Acquisition Mechanism (TAGSAM), and transited across Bennu while descending about a half-mile (805 meters) toward the surface. After a four-hour descent, at an altitude of approximately 410 feet (125 meters), the spacecraft executed the “Checkpoint” burn, the first of two maneuvers to allow it to precisely target the sample collection site, known as “Nightingale.”

Ten minutes later, the spacecraft fired its thrusters for the second “Matchpoint” burn to slow its descent and match the asteroid’s rotation at the time of contact. It then continued a treacherous, 11-minute coast past a boulder the size of a two-story building, nicknamed “Mount Doom,” to touch down in a clear spot in a crater on Bennu’s northern hemisphere. The size of a small parking lot, the site Nightingale site is one of the few relatively clear spots on this unexpectedly boulder-covered space rock. ...

All spacecraft telemetry data indicates the TAG event executed as expected. However, it will take about a week for the OSIRIS-REx team to confirm how much sample the spacecraft collected.

Real-time data indicates the TAGSAM successfully contacted the surface and fired a burst of nitrogen gas. The gas should have stirred up dust and pebbles on Bennu’s surface, some of which should have been captured in the TAGSAM sample collection head. OSIRIS-REx engineers also confirmed that shortly after the spacecraft made contact with the surface, it fired its thrusters and safely backed away from Bennu. ...

To store the sample, engineers will command the robotic arm to place the sample collector head into the Sample Return Capsule (SRC), located in the body of the spacecraft. The sample arm will then retract to the side of the spacecraft for the final time, the SRC will close, and the spacecraft will prepare for its departure from Bennu in March 2021 -- this is the next time Bennu will be properly aligned with Earth for the most fuel-efficient return flight.

If, however, it turns out that the spacecraft did not collect enough sample at Nightingale, it will attempt another TAG maneuver on Jan. 12, 2021. If that occurs, it will touch down at the backup site called “Osprey,” which is another relatively boulder-free area inside a crater near Bennu’s equator. ...
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OSIRIS-REx Collects Significant Amount of Asteroid

Post by bystander » Sat Oct 24, 2020 3:47 pm

OSIRIS-REx Collects Significant Amount of Asteroid
NASA | GSFC | OSIRIS-REx | 2020 Oct 22
Two days after touching down on asteroid Bennu, NASA’s OSIRIS-REx mission team received on Thursday, Oct. 22, images that confirm the spacecraft has collected more than enough material to meet one of its main mission requirements – acquiring at least 2 ounces (60 grams) of the asteroid’s surface material.

The spacecraft captured images of the sample collector head as it moved through several different positions. In reviewing these images, the OSIRIS-REx team noticed both that the head appeared to be full of asteroid particles, and that some of these particles appeared to be escaping slowly from the sample collector, called the Touch-And-Go Sample Acquisition Mechanism (TAGSAM) head. They suspect bits of material are passing through small gaps where a mylar flap – the collector’s “lid” – is slightly wedged open by larger rocks.

The team believes it has collected a sufficient sample and is on a path to stow the sample as quickly as possible. They came to this conclusion after comparing images of the empty collector head with Oct. 22 images of the TAGSAM head after the sample collection event.

The images also show that any movement to the spacecraft and the TAGSAM instrument may lead to further sample loss. To preserve the remaining material, the mission team decided to forego the Sample Mass Measurement activity originally scheduled for Saturday, Oct. 24, and canceled a braking burn scheduled for Friday to minimize any acceleration to the spacecraft.

From here, the OSIRIS-Rex team will focus on stowing the sample in the Sample Return Capsule (SRC), where any loose material will be kept safe during the spacecraft’s journey back to Earth. ...
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