MIT Technology Review: “There’s so much in there that the sample is now escaping,” Thomas Zurbuchen, NASA’s associate administrator for science, said.
What was supposed to happen: On Tuesday 20th Oct , OSIRIS-REx descended to asteroid Bennu (the object it has studied from orbit for almost two years now, more than 200 million miles from Earth) and scooped up rubble from the surface during a six-second touchdown before flying back into space. The goal was to safely collect at least 60 grams of material, and the agency expected to run a series of procedures to verify how much was collected.
Those included observations of the sample collection chamber using onboard cameras, as well as a spin maneuver scheduled for Saturday that would approximate the sample’s mass through moment-of-inertia measurements.
What actually happened: Over the last few days, the onboard cameras revealed that the collection chamber was losing particles that were floating into space. “A substantial amount of the sample is seen floating away,” mission lead Dante Lauretta said Friday. As it turned out, the sample collection attempt picked up too much material—possibly up to two kilograms, the upper limit of what OSIRIS-REx was designed to collect.
About 400 grams seems visible from the cameras. The collection lid has failed to close properly and remains wedged open by pieces that are up to three centimeters in size, creating a centimeter-wide gap for material to escape. It seems when OSIRIS-REx touched down on Bennu’s surface, the collection head went 24 to 48 centimeters deep, which would explain how it recovered so much material.