The historic collection of a sample from the near-Earth asteroid Bennu by NASA’s OSIRIS-REx spacecraft on Tuesday was almost too successful.
Some of the sample is leaking into space, according to Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona in Tucson during a NASA press conference Friday.
“The big concern now is that particles are escaping because we’re almost a victim of our own success,” he said. “Large particles left the flap open. Particles are diffusing out into space. They aren’t moving fast, but nonetheless, it’s valuable scientific material.”
The mission team analyzed images Thursday taken of the collector head of the spacecraft that showed that a substantial sample was collected — but there is so much material in the head that the flap designed to keep the sample inside is jammed.
This is allowing particles to escape into space. The mission team is changing the course of the events planned for the spacecraft this weekend and planning to stow the sample as quickly as possible so little material is lost. The researchers estimated that it’s continually losing between 5 to 10 grams of material. This flaky material floats in what resembles a cloud of particles around the head.
But the team isn’t sure of the exact loss rate because it’s not steady.
The mission was required to collect at least 2 ounces, or 60 grams, of the asteroid’s surface material. Based on the images they analyzed, the researchers are confident that the collector head on the end of the spacecraft’s robotic arm actually captured 400 grams of material. And that’s only what’s visible to them through the perspective of the camera.
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But particles are escaping through small gaps where a Mylar flap, or lid, is being held open by at least a centimeter by large rocks. And the activities planned for the spacecraft this weekend could cause more sample loss due to movement.
Previously, OSIRIS-Rex was expected to conduct a braking burn on Friday and a measurement of the sample’s mass on Saturday. Although this means the team won’t know the true mass of the sample until it returns to Earth in 2023, the mission team is confident that it will have a sufficient sample.
“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,” Lauretta said. “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 team will go through another evaluation process this weekend to ensure that the sample head could be stowed in the sample return capsule