NASA has announced that the first visual inspection of the OSIRIS-REx space probe’s TAGSAM system, which captured soil samples from asteroid Bennu in the night between 21 and 22 October, has done its job well. In fact, the problem appears to be that the mechanism captured far too many materials and, after OSIRIS-REx moved away from Bennu, they started escaping. For this reason, the mission team decided to skip the various operations that would have allowed more significant examinations of the samples to try to seal them in the Sample Return Capsule to bring them back to Earth.
The images that arrived at NASA after the end of the TAG (Touch-And-Go) event showed that it was completely successful, perhaps even too successful. The OSIRIS-REx space probe landed on the surface of asteroid Bennu, where the TAGSAM (Touch-And-Go Sample Acquisition Mechanism) system, the one that physically touched the ground, almost immersed itself in the regolith, the most superficial layer, formed largely of stones, pebbles of various sizes, and dust. TAGSAM’s head appears to crush the porous materials on the surface, a clue confirming the theory that Bennu is made up of debris generated by a collision between asteroids that coalesced again. The pressurized nitrogen container scattered around a lot of materials and some were captured by TAGSAM’s head.
Physical contact with the surface of asteroid Bennu lasted only 6 seconds, during which time TAGSAM probably captured well over the 60 grams established by NASA scientists as the minimum to consider the operation satisfactory. A slightly larger pebble might have got stuck on the edge of TAGSAM’s head preventing the capture mechanism from closing completely. The consequence is that small fragments started escaping, and are visible in the image (NASA).
Further maneuvers of the OSIRIS-REx space probe were scheduled but were canceled to try to correctly place the samples in the Sample Return Capsule (SRC). The maneuver called Sample Mass Measurement was supposed to be used to estimate the mass of the samples but could lead to further losses. A breaking burn by OSIRIS-REx could also aggravate the problem and is not urgent. This means that the priority is to seal the samples to avoid further losses.
Dante Lauretta, the principal investigator of OSIRIS-REx, who heads the mission’s science and operations team, explained that he and his colleagues are working to bring back as large samples of Bennu as possible. Mass loss is a concern, so he’s strongly encouraging the team to stow the precious samples as quickly as possible.
The TAG event showed that on a space mission, things can go even better than expected and still cause problems. In the case of asteroid Bennu, the surprise came from the fact that its surface is covered with stones, pebbles of various sizes, and dust. This probably made it possible to collect more materials than expected but also created problems for the collection mechanism. However, NASA can hope that the OSIRIS-REx space probe will bring back enough samples to Earth to examine materials that remained undisturbed for who knows how long.
