(C) Daily Kos
This story was originally published by Daily Kos and is unaltered.
. . . . . . . . . .
Samples from asteroid Bennu set to be delivered to Earth Sunday morning [1]
['This Content Is Not Subject To Review Daily Kos Staff Prior To Publication.']
Date: 2023-09-20
This Sunday morning, just before 7 A.M. Eastern, NASA will trasmit one of two brief signal s to the OSIRIS-REx spacecraft as it nears Earth:
“Yes” or “No”.
Should the spacecraft drop a capsule into Earth’s atmosphere that contains material it took from near-Earth asteroid Bennu for collection in the Utah desert later that morning?
Principal investigator Dante Lauretta gives it a 99% chance that we’re going to get a “Yes”.
"The spacecraft is very healthy," Lauretta said. "We have a good vehicle."
If it is indeed “Yes”, NASA TV will begin livestreaming the collection event at 10 A.M. Eastern. Four helicopter pilots will take off at around 10:40 A.M. for perhaps the most important flight of their lives. They’ll begin circling the 300-square-mile recovery area just as the Sample Return Capsule (SRC) enters Earth’s atmosphere at 10:42 A.M. over the California coast. At about 10:50 A.M., the SRC will deploy its parachute a mile up, and it’s expected to hit the ground in Utah at 10:55 A.M. A seven-year mission, and NASA’s got it all down to the minute.
Within two hours, the material from Bennu will be safely in a cleanroom on the grounds of Dugway Proving Ground . We’ll find out then exactly how much material was collected, but visuals from the mission put the approximate weight at half a pound. The previous record for asteroid sample recovery belongs to JAXA’s Hayabusa2 mission, which collected and returned 5.4 grams, or about a teaspoon, of material from asteroid Ryugu in late 2020. That was a truly awesome pioneering effort, and now we’re ready for the next step, about to eclipse it on a weight basis by about 50x.
You might remember the famous video from October 2020 of the OSIRIS-REx sampler smashing into Bennu’s surface to load up:
That white circle at the end of the sampler arm is called the TAGSAM (Touch-And-Go Sample Acquisition Mechanism). It has a capacity of up to about 4 pounds of bulk material, and it also has 24 Velcro-like spots that can grab small amounts of fine material from the surface.
The original plan was to weigh the material captured inside the TAGSAM head right up there on Bennu, but some of the material got wedged in the Mylar overlay sheet that was supposed to prevent sample leakage out of the sampler head, and as a result, some material was leaking out anyway.
Captured by the spacecraft's SamCam camera on Oct. 22, 2020, this image shows that the sampler head on NASA's OSIRIS-REx spacecraft is full of rocks and dust collected from the surface of the asteroid Bennu. They show also that some of these particles are slowly escaping the sampler head through small gaps where the head's mylar flap is wedged open.
So the whole TAGSAM head was stowed away into the SRC without delay to prevent any more loss, and there wasn’t time to take an accurate weight. But the visually estimated half-pound of material tops the mission success criterion (60 grams or more) by a comfortable margin.
The TAGSAM head is stowed within the SRC aboard the OSIRIS-REx spacecraft
As the SRC touches down on Earth Sunday morning, its parachute will detach, and it will be left lying face-down in the desert. On July 18 of this year, in the final rehearsal at the landing site, a replica SRC was dropped by a helicopter to mimic Sunday’s events. Here a U.S. Army representative arrives first at the scene to ensure that the capsule is safe for handling and to assess its intactness:
A military representative rehearses his initial approach to the Sample Return Capsule on Tuesday, July 18 in Utah
Then a cargo net is secured around the capsule…
OSIRIS-REx team members practice getting a mock Sample Return Capsule packed for its helicopter flight to a clean room on the Department of Defense’s Utah Test and Training Range on Wednesday, July 19
..and it is whisked away by helicopter to the cleanroom:
A helicopter practices transporting a mock Sample Return Capsule on Wednesday, July 19.
It’s very cool to see that the U.S. Army is very much on board with the excitement around the completion of this mission. The material will first go to NASA’s Johnson Space Center in Houston, but scientists in Japan, France, Australia, the UK, and elsewhere in the U.S. are pumped too, because they’ll all be getting some. And with half a pound of material, there’ll be plenty to go around. This is an unprecedented bonanza for international research!
That half-pound of material is coming from what was previously just a ghostly radar image from an asteroid measuring 1,600 feet in diameter that we didn’t even know existed until 1999:
Radar data on Bennu from the now-defunct Arecibo radio telescope, and the 3-D model that was put together as a result
OSIRIS-REx brought that to life with images like this, from about 50 miles out:
Bennu from about 50 miles away
So of all the asteroids out there, why did we pick Bennu? Lauretta co-authored a book that just came out in August that contains this very digestible explanation:
A pictorial explanation of why Bennu fits the bill
Bennu isn’t merely carbon-rich, though. Spectral data suggest it’s most similar to CI-type chondrite meteorites we’ve recovered on Earth. Of the 20,000 or so meteorites we’ve recovered, only 5 CI-type chondrites are known, and among these, only 3 weigh more than a few grams. The largest is the Orgueil meteorite, which fell as at least 20 chunks weighing a total of about 31 pounds. The Smithsonian has a chunk of it that weighs a little over an ounce:
Of all the carbon-rich meteorite types, CI’s are by far the closest match to the elemental composition of the Sun itself (except for elements that can be part of volatile compounds and escape, like hydrogen, oxygen, etc.), suggesting they contain the most pristine material from the formation of the whole Solar System. Look at this great match of the Orgueil meteorite’s elemental composition to that of the Sun’s photosphere:
Orgeuil’s elemental concentrations plotted against those determined for the solar photosphere. These are plotted on a log scale per 10^12 hydrogen atoms, so hydrogen would appear at 12 (off the chart). We can see lead at about 2, so there are about 10^2 = 100 lead atoms for every 10^12 = 1 trillion hydrogen atoms.
When we line up CI-type meteorites to other carbon-rich types, we see that the others, to varying degrees, are depleted in some lighter elements like sodium (Na) and potassium (K) and/or have spikes in heavier ones like nickel (Ni) and cobalt (Co). The straight line at “1” below is set for the composition of CI’s, and then all the other types are plotted against that to show you the deviations:
Other types of carbon-rich meteorite elemental abundances plotted relative to those of the CI-type. For easy comparison, all the CI elemental abundances are set to 1 (straight line that runs across each graph). So in the graph on the right, for example, we see from the triangle at the very upper left that osmium (Os) is 6x as concentrated in a CB-type meteorite as in a CI-type.
All of that is what makes CI-type meteorites kind of special, and we think, especially from looking at its infrared spectrum, that Bennu is most likely of this rare CI type.
Bennu's thermal infrared spectrum, part of which is shown here, is similar to the most primitive types of carbonaceous chondrites, especially CI
But what’s so interesting about testing Bennu samples if we already know what they’re made of? Well, even though we do have a good idea of the elements Bennu is made of, the way those elements are arranged into molecules should tell us a lot about Bennu’s history.
The problem with meteorites we find on Earth, of course, is that the harsh entry into Earth’s atmosphere — and then also the sitting around on Earth until they’re found — alters them significantly, and it’s impossible to know for sure what the extent of these changes is. Here, though, we will get a chance to analyze one that has been altered only by its history away from Earth. It will be by far the largest sample we have ever had a chance to do this with.
We do have a working storyline of how Bennu and asteroids like it came to be, and labs around the world will use around 70 different analytical techniques to test our hypotheses about that. We think Bennu originally formed out around Jupiter, like all the other carbon-rich asteroids. But now it’s a mildly hazardous near-Earth asteroid, with an estimated 0.04% chance to strike Earth on September 24, 2182, 159 years to the day after its sample delivery.
Bennu’s orbit relative to Earth. Notice Bennu’s orbit is tilted slightly with respect to earth’s orbit, crossing Earth’s orbit only in late September
It’s thought to have been pushed inward toward the Sun after its formation by the Yarkovsky effect , where a dark asteroid like Bennu can absorb a lot of heat on its daylight side, then, when the heated surface rotates to nighttime, it releases that heat and actually produces a small thrust. In fact, study of Bennu samples will help predict further changes in its orbit by the Yarkovsky effect and hone our predictions of the likelihood of Bennu and other asteroids hitting Earth. Kind of a good thing to know.
We also think that Bennu was originally part of a larger “parent” asteroid, some of whose material got knocked loose by a major impact with another object. Some of the fragments of that impact were gravitationally attracted back together into other smaller bodies like Bennu, and that’s why Bennu is basically a pile of boulders held together by weak gravity.
That and other impacts probably heated the parent asteroid from time to time, and this was enough to cause water to react with the mineral components and change their nature, in a process called “aqueous alteration”, which can be quantified by analyzing the state of those minerals. Once Bennu formed in its own right, it may also have had a closer approach to the Sun at one time than it does now, and that heating could have further altered its molecular nature. But these types of heating are nothing compared to entry into Earth’s atmosphere, which vaporizes most meteors altogether by heating them to over 3000°F. So that’s one of many reasons that study of these returned samples, protected from the effects of reentry by the Sample Return Capsule, is such a great opportunity.
One other very cool part of this is that we will be able to catch just about all of the modestly volatile material from Bennu, which we can’t do very well at all with meteorites. When carbon-rich meteorites are recovered on Earth, they generally have a pretty pungent smell. That’s because they contain life-friendly organic compounds, many of which are pretty lightweight and can vaporize fairly easily. The odors from these meteorites have been described as compost, vanilla, Brussels sprouts, methylated spirits, wet hay, tar, and other things. And yet by the time meteorites hit Earth and get recovered, they’ve already lost a lot of their volatile material. So the stuff from Bennu should be absolutely loaded and unaltered, containing volatiles we have never seen in meteorites. It’ll give us a better idea of what kinds of specific life-friendly organic molecules can routinely form in space (and hence could have been present on early Earth).
What will the Bennu material smell like? Maybe a new fragrance will be inspired...
Meteor by Coty: launched in 1949 in France and in the USA by 1951
Bennu is named for an avian Egyptian deity whose name is derived from a term meaning "to rise in brilliance" or "to shine".
The deity was said to have flown over the waters of Nun that existed before creation, landing on a rock and issuing a call that determined the nature of creation. He also was a symbol of rebirth and, therefore, was associated with Osiris.
I see what you did there, NASA!
The Egyptian deity Bennu
Belly’s reunion album “Dove” contains an uncannily perfect and superbly produced video tribute to Bennu, intentionally or not: the very avian “Shiny One” (oh yeah, and it’s a great song, too!)…..
[END]
---
[1] Url:
https://www.dailykos.com/stories/2023/9/20/2191410/-Samples-from-asteroid-Bennu-set-to-be-delivered-to-Earth-Sunday-morning
Published and (C) by Daily Kos
Content appears here under this condition or license: Site content may be used for any purpose without permission unless otherwise specified.
via Magical.Fish Gopher News Feeds:
gopher://magical.fish/1/feeds/news/dailykos/
