NASA confirmed this afternoon that indeed its sampling of the ancient asteroid Bennu was successful and that the OSIRIS REx spacecraft had obtained a scientifically significant amount of material from the surface. But the mission team noted that a portion of the sample itself is continually being lost through gaps in the spacecraft’s collecting lid.
Even so, the OSIRIS-REx Mission Planning board voted this evening to forgo a second attempt at resampling the surface, Jason Dworkin, the mission’s project scientist at NASA’s Goddard Spaceflight Center in Maryland, told me.
The team says images from the spacecraft indicate that the sampler collected at least 2 ounces (60 grams) of the asteroid’s surface material. Estimates at this stage are that some 10 grams of the sample may have already been lost, Thomas Zurbuchen, Associate Administrator for Science at NASA Headquarters in Washington, D.C., told me.
“We are doing everything we can now to minimize the loss of the sample we have,” said Dworkin. “Every particle is precious and hard-earned.”
The team first noticed there was a problem after reviewing images of the sample collector head as it moved through several different positions, says NASA. They noticed that some of the collected asteroid particles appeared to be escaping slowly from the sample collector, called the Touch-And-Go Sample Acquisition Mechanism (TAGSAM) head, says the agency. NASA says they suspect that bits of material are passing through small gaps where a mylar flap — the collector’s “lid” — is wedged slightly open by larger rock samples.
“Our focus is on making sure that we only move the arm as little as possible,” said Zurbuchen.
The team fears that any further movement to the spacecraft and the TAGSAM instrument may lead to further sample loss, says NASA. Thus, the team has decided to forgo A Sample Mass Measurement activity originally scheduled for Saturday, Oct. 24.
Instead, NASA says the team will focus on stowing the sample in the Sample Return Capsule (SRC).
“Once the TAGSAM head is sealed in the sample return capsule no additional material will be lost,” said Dworkin. “Probably nothing more will need to be done once the sample is safely secured in the sample return canister.”
As for the sample itself?
NASA reports that the collector head was flush with Bennu’s surface when it made contact. It’s thus thought that the sample contains material from several centimeters beneath the asteroid’s brittle surface.
And although the surface of the asteroid proved more risky than initially envisioned, the mission team and the spacecraft were able to meet the challenge.
The team had to adapt in real time to what they found (saturated surface, few sandy “beach like” places), and did a great job finding a sample collection site, says Zurbuchen.
Despite technical glitches, NASA has already learned much about the art of sampling asteroids from this mission alone.
Technologies employed and perfected on OSIRIS-REx could be applied to future missions, says Zurbuchen. We intend to do Mars Sample Return in the 2030s, he says.
One goal of such missions is to learn more about the morphology and structure of these ancient bodies in order to better protect us from near earth asteroids that might threaten Earth.
“Our time at Bennu has helped us understand potentially dangerous asteroids even more,” said Zurbuchen.
The spacecraft itself remains in optimal operational condition and although it is no longer in actual orbit around the ancient asteroid, it remains in the vicinity in a stationkeeping position.
Then next March, when the orbital mechanics are optimal, it will begin its two and a half year journey back to Earth.
The sample returns to Earth in September 2023, says Zurbuchen. We expect scientists will study this sample for generations and indeed a portion of it will be reserved for later study with technologies we haven’t invented yet and to answer questions we haven’t thought to ask yet, he says.