OSIRIS-REx has been in orbit of Bennu since late 2018, which gave NASA ample time to find just the right landing zone on the unexpectedly rocky surface. It apparently chose well. Following the recent successful touch and go operation, NASA has reported a sizeable sample of the asteroid has now been locked away in the probe’s sample return container.
Earlier this month, OSIRIS-REx descended and tapped the surface, or rather, it was supposed to be a tap. NASA now says the sampling arm may have punched through 19 inches (48 centimeters) of loose soil before the nitrogen blast fired. That puff of air was supposed to blow about 60g of material into the sampling container. Instead, it harvested a whole lot more.
There was a brief but scary period earlier this week when NASA confirmed that large pebbles had jammed open the sample container’s lid. As a result, asteroid particles were falling out whenever the spacecraft moved. NASA opted to forego the planned sample measurement over the weekend as that would have caused more sample material to drift away. It also scrapped any plans to conduct a second sampling run at the backup Bennu site. Instead, NASA worked to secure its impressive haul.
The latest images from OSIRIS-REx show the sample safely locked inside the sample capsule. This module will eventually drop into Earth’s atmosphere, and the heat shield will protect it from atmospheric reentry. We don’t know exactly how much sample OSIRIS-REx grabbed from Bennu, but we know it’s a lot more than the 60g minimum. NASA estimates OSIRIS-REx could have as much as a kilogram (1,000g or 2.2 pounds) of pristine asteroid soil in the return canister. That’s huge — the payloads of past sample return missions could best be measured in milligrams. The recent Hayabusa2 mission hopes to have 100mg (a tenth of a gram) of asteroid regolith when it lands in the coming months.
Getting that much of Bennu back to Earth could be a watershed moment for science. Most asteroid samples on Earth have been scorched by the atmosphere and smashed to bits on impact. Bennu has remained mostly unchanged since the formation of the universe, and we’ll have enough for lots of teams to run lots of tests that will no doubt teach us a great deal about the early solar system.
Bennu and OSIRIS-REx are currently millions of miles away, so it’ll take time for the probe to return home. NASA plans to break orbit in March 2021 when Bennu and Earth are in close proximity. The sample return capsule should be back on Earth in September 2023.
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