NASA’s OSIRIS-REx mission had an unexpected explosion in October 2020 while landing on asteroid Bennu to collect a valuable sample to take home to Earth.
In two new studies, mission scientists have described a dramatic search for a sample that led to surprising discoveries about the nature of an asteroid. The results aren’t just interesting: The researchers say the findings could have implications for a possible future warp mission, if it’s 1,640 feet (500 meters) wide. Bennu (One of the riskiest known near-Earth asteroids) never threatens to impact the planet.
“We expected the surface to be quite rough, like if you touch a pile of gravel: some dust flies and a few particles rise up,” says University of Arizona planetary scientist and director Dante Lauretta. an investigator for OSIRIS-REx, the mission told Space.com.
“But when we got the footage back after the incident, we were stunned,” he said. “We saw a huge wall of debris flying from the side of the sample. It was really scary for the spacecraft operators.”
Related: Asteroid Bennu’s mysterious missing craters suggest ‘shock armor’ protecting the surface
The outcome of the impact was so unexpected that Lauretta, lead author of one of the two studies, campaigned for the spacecraft to revisit the area to figure out what happened. Six months after collecting the samples, in April 2021, the researchers had another insight OSIRIS-REx touch site. When the spacecraft first reached Bennu, the site, called Nightingale, was sitting in a 65-foot-wide (20 m) impact crater. After touchdown, mission scientists found a new 26-foot-wide (8 m) gap in the surface, with debris and rocks scattered around the surface.
This is a surprisingly large scar; The scientists expected to remove a bit as wide as the sampler itself, up to 12 inches (30 centimeters) wide. “But we sunk,” said Lauretta. “Obviously there was no resistance. The surface was soft and flowed like a liquid.”
The probe sank as deep as 30 inches (70 cm) and revealed pristine material that, unlike the asteroid’s surface, had not been altered by repeated impacts. cosmic rays and solar windStreams of high-energy particles from the Sun.
Based on measurements taken during this return visit, Lauretta’s team calculated that the density of the surface material was only 31 to 44 pounds per cubic foot (500 to 700 kilograms per cubic meter). In comparison, “typical Place the rock “has a density about six times higher, at 190 pounds (3,000 kilograms) per cubic foot per cubic meter.
A second study based on measuring the forces applied to the probe during impact confirmed these figures.
“The [surface] the rocks are very porous and have a lot of space between them,” Kevin Walsh, a geologist at Southwest Research Institute in Colorado and lead author of the second study, told Space.com. the dust would stick to the large rocks and act as glue to fill the gap and provide some strength to allow the surface to push the spacecraft further. But it’s not there.”
Bennu’s soft, feathery nature could complicate a possible future tilt attempt if astronomers identify any rock hazards that could hit Earth. At 1,640 feet wide, Bennu’s impact will cause continental-scale disruption to our planet. Although NASA estimates the chance of a collision 1 in 2700 between 2175 and 2199Bennu is still one of the most dangerous asteroids currently known.
Moreover, scientists believe that many asteroids have a similar “rubble pile” structure: essentially conglomerations of rock, gravel, and dirt held together by weak gravitational forces. The sampling experience at Bennu shows that it is almost impossible to predict how such a debris pile will react to an impact.
“Touch provided the first experience of actually pressing something on a surface,” Walsh said. “And if we ever go and try to entertain something like that, we need to know what the surface is so it doesn’t just absorb the effect.”
Lauretta added that the subsurface material appeared redder than Bennu’s blue surface, indicating the presence of cosmic rays and other forms. space weather erode exposed space rocks. Red colors indicate that the asteroid may contain organic molecules such as hydrocarbons, which are of great interest to researchers trying to understand the origin of life on Earth.
Scientists will have to wait for the planned delivery of OSIRIS-REx in September 2023 to obtain the precious material. During the dramatic sampling effort, the probe collected almost 9 ounces (250 grams) of asteroid dust, slightly less than the teams expected, but still four times more than needed for analysis, Lauretta said.
The OSIRIS-REx mission was recently extended and after the spacecraft drops its payload to Earth next year He will go to ApophisAnother high-risk asteroid to visit in 2029.
The results are described in articles published Thursday (July 7) in the journal Science and Advances in science.
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