IN A FIRST-OF-ITS-KIND mission for NASA, dust and rocks collected from an asteroid streaked through the Earth’s atmosphere in a capsule and landed in a military range in Utah on Sunday. As the capsule dashed through the sky, its surface was searing hot, but the sample inside was protected by a heat shield made in Silicon Valley’s NASA Ames Research Center.
According to Ethiraj Venkatapathy, chief technologist for the division that invents thermal protection systems, the heat shield is only a little more than 2 inches thick of a material that is lightweight enough to float on water.
“Two inches away from the surface [of the capsule], the temperature is tens of thousands of degrees,” he said. “The surface is 5,000 degrees Fahrenheit, but two inches below you can touch it.”
On Sept. 8, 2016, NASA launched the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer — called OSIRIS-REx for short. The spacecraft’s mission was to go to an asteroid, Bennu, to collect a sample of rocks and dust from the surface. On Sunday, the spacecraft delivered the capsule with the samples to Earth.
The sample collected from Bennu, a primordial rock in space, can help scientists answer the question “Why are we here?”
The asteroid was created with the formation of the solar system and has elements that were created at that time, around 4 billion years ago. It has carbon and water that make life, Venkatapathy said.
OSIRIS-REx science team predicts that Bennu, well into the future, could impact Earth on Sept. 24, 2182. Although it is a small probability, according to Venkatapathy, the sample can help decide preventive actions.
“Asteroids impacts have been happening for millions of years and that there’s a hypothesis that they brought water and they brought life, you know, through carbon and other things,” he said. “What other minerals would it have? So those kinds of questions become answerable only when we have samples in our hand.”
Touch and go
Bennu is a 500-meter asteroid with very low gravity. Venkatapathy said even a feather touch could have a response and OSIRIS-REx had to perform very fine maneuvers to collect the samples. On Oct. 20, 2020, OSIRIS-REx briefly touched down on Bennu to collect dust and pebbles from its surface in a maneuver known as ‘Touch-And-Go.’ The spacecraft delivered around 250 grams (about 8.82 oz) of materials, with a likely variation of 101 grams.
NASA Ames also played a crucial role in designing methods for the mission to collect high-quality samples, save them in pristine form, and develop a plan for the scientific community to study the fundamentally irreplaceable asteroid material.
“[I]t’s part of our core capability to contribute to a mission like that, and that’s very exciting because these missions take decades.” Ethiraj Venkatapathy, NASA Ames Research Center chief technologist
“The science community at NASA Ames, the engineering community, specifically the thermal protection system, it’s part of our core capability to contribute to a mission like that, and that’s very exciting because these missions take decades,” Venkatapathy said. “And so (Sunday) was all of that coming together.”
The capsule parachuted to the Department of Defense’s Utah Test and Training Range on Sunday and touched down at 9:55 a.m. Central time, where the OSIRIS-REx team was waiting to retrieve it. According to Venkatapathy, the best part of the touchdown was that the capsule sat on its pointy nose, as if waiting for the team.
“It was picture perfect,” he said.
The anticipation was palpable during the landing, he said. He was present for the landing of Genesis in 2004 — a mission to collect samples of the solar wind — when the parachute didn’t open and it crashed. So, the team will be analyzing the lessons learned on Sunday. He also mentioned that the principal investigator looking at the delivered capsule said that the heat shield was as charred as it was supposed to be and nothing looked out of the ordinary.
“But we will be asking a lot more in-depth questions,” Venkatapathy said. “We may do more analysis to understand. Did it behave the same way as we expected?”
This has implications for future missions because the material used on this mission, called Phenolic-Impregnated Carbon Ablator (PICA), was used before in the Stardust mission, the first spacecraft to bring samples from a comet to Earth, and will continue to be used. According to him, the one-of-a-kind Arc Jet Complex at NASA Ames helps test these materials.
Analyzing the data
According to NASA’s blog updates, the team on Sunday first secured the sample and checked the area where it landed before starting the recovery process, which the team had practiced several times over the past year. The 100-pound capsule was wrapped and secured in a crate in a harness and then flown to a temporary “clean room” by the long-line helicopter. The scientists collected soil and air samples from the area to catalog everything the capsule could have been exposed to in order to account for contamination.
Packed in shipping containers along with the environmental samples, the items were delivered Monday to their permanent home at NASA’s Johnson Space Center in Houston, where they will be cared for and stored. Members of Ames’ thermal protection team also plan to laser-scan the OSIRIS-REx heat shield in coordination with colleagues at NASA’s Johnson Space Center in Houston, Lockheed Martin, or both.
Over the next two years, the science and curation teams will catalog the sample and conduct the analysis needed to meet the mission’s science goals. Approximately six months later, a sample catalog will be released, and samples from Bennu will also be distributed to around 200 scientists around the world. It was a multigenerational effort, Venkatapathy said, and the samples will be made available for future generations to study.
A Japanese spacecraft Hayabusa2 brought samples from asteroid Ryugu in 2020. According to Venkatapathy, Ryugu and Bennu are different kinds of asteroids and the analyses will complement each other.
OSIRIS-REx, which remains in space, now has a new target, asteroid Apophis, and has been renamed OSIRIS-APEX for OSIRIS-Apophis Explorer.
