DETROIT – Two days after touching down on asteroid Bennu, NASA’s OSIRIS-REx mission team has received images that confirm the spacecraft has collected more than enough material to meet one of its main mission requirements – acquiring at least two ounces of the asteroid Bennu’s surface material.
Quoting NASA, it’s a “large amount!” 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 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.
Essentially, mission scientists are a victim of their own success: the sample capture worked too well!
I participated in a live NASA teleconference late this afternoon, and OSIRIS-REx principal investigator, Dante Laurette, says that a rock has wedged that flap open about a centimeter (between a third and a half of an inch).
As you can see in this series of three images taken of the TAGSAM head, there are little bits of stuff flying around...that’s some of the regolith (“dirt”) captured by the spacecraft.
“Bennu continues to surprise us with great science and also throwing a few curveballs,” said Thomas Zurbuchen, NASA’s associate administrator for science at the agency’s headquarters in Washington, and a former professor and researcher at the University of Michigan.
“And although we may have to move more quickly to stow the sample, it’s not a bad problem to have. We are so excited to see what appears to be an abundant sample that will inspire science for decades beyond this historic moment.”
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, and canceled a braking burn scheduled for Friday to minimize any acceleration to the spacecraft.
The less force the spacecraft exerts, the less disturbed the sample in the collector is which, in the weightless environment of space, acts more like a fluid.
Think of it this way: you are holding a glass of water filled to the brim. If you don’t want to lose any of that water, you move the glass as little as possible.
The OSIRIS-Rex team will now 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. This should happen early next week.
“We are working to keep up with our own success here, and my job is to safely return as large a sample of Bennu as possible,” said Lauretta, who leads the science team and the mission’s science observation planning and data processing.
“The loss of mass is of concern to me, so I’m strongly encouraging the team to stow this precious sample as quickly as possible.”
The TAGSAM head performed the sampling event in optimal conditions. Newly available analyses show that the collector head was flush with Bennu’s surface when it made contact and when a nitrogen gas bottle was fired to stir surface material. It also penetrated possibly as deep as eighteen inches into the asteroid’s surface material.
All data so far suggest that the collector head is holding much more than two ounces of regolith.
Once the sample is safely stowed away, the spacecraft will stay in orbit around Bennu until it and Earth are in such a position in their orbits that OSIRIS-REx will then fire its engines (likely this March) and head back home, where the capsule with the precious asteroid sample will parachute to a landing target in Utah in 2023.