NASA’s OSIRIS-REx mission unleashed an unexpected explosion when it landed on asteroid Bennu in October 2020 to collect a precious sample for transport back to Earth.
Mission scientists describe the exciting sample retrieval process, which has led to surprising discoveries about the nature of the asteroid, in two new studies. And the results aren’t just intriguing: The researchers say the findings could have implications for a possible future skew mission, if it were 1,640 feet (500 metres) across. beno (One of the most dangerous near-Earth regions known asteroids) threatens to affect the planet.
“We expected the surface to be very solid, kind of if you touch a pile of pebbles: a little dust is flying away and some particles are jumping up,” Dante Loretta, a planetary scientist at the University of Arizona and director of investigators for OSIRIS-REx, told Space.com. .
“But while we were bringing back the photos after the event, we were blown away,” he continued. “We saw a huge wall of debris flying away from the side of the sample. For spacecraft operators, it was really scary.”
Related: Mysterious missing craters of asteroid Bennu suggest ‘collision shielding’ protects the surface
The effects of the shock were so unexpected that Loretta, the lead author of one of the two studies, campaigned for the spacecraft to revisit the area to understand what had happened. Six months after collecting samples, in April 2021, researchers got another glimpse of Osiris Rex landing site. When the spacecraft first reached Bennu, that location, called Nightingale, sat inside a 65-foot-wide (20-meter) impact crater. After landing, expedition scientists found a new hole 26 feet (8 meters) wide in the surface, with rubble and boulders scattered around the site displaced.
This is a surprisingly large scar. The scientists had expected to extract a little like the sample complex itself, 12 inches (30 cm). “But we drowned,” Loretta said. “Obviously there was no resistance at all. The surface was smooth and flowing away like a fluid.”
The probe sank to a depth of 30 inches (70 cm), revealing a pure substance that, unlike the surface of the asteroid, had not been altered by the continuous beating of cosmic rays and the solar windstreams of high-energy particles from the sun.
From measurements obtained during this repeat visit, Loretta’s team calculated that the density of surface material was only about 31 to 44 pounds per cubic foot (500 to 700 kilograms per cubic meter), according to Loretta. For comparison, “typical a land The rock “has a density nearly six times higher, such as 190 pounds per cubic foot (3,000 kg) per cubic meter.
A second study, based on measurements of the forces acting on the probe during impact, confirmed these numbers.
“The [surface] The rocks are very porous and there are a lot of empty spaces between them, Kevin Walsh, a geologist at the Southwest Research Institute in Colorado and lead author of the second study, told Space.com. The dust will stick to the larger rocks and fill the space and act as a paste to provide some strength, allowing the surface to press on the spacecraft more. But it doesn’t exist.”
Bennu’s soft, smooth nature may complicate a possible aberration attempt in the future, if astronomers determine that the rocks threaten to strike Earth. At 1,640 feet, a strike by Bennu would cause continent-wide disruption to our planet. Although NASA estimates the chance of a collision in 1 in 2700 between the years 2175 and 2199Bennu is still one of the most dangerous asteroids known today.
Moreover, scientists hypothesize that many asteroids are similar in composition to a “rubble pile”: aggregates of rocks, gravel, and dirt held together by weak gravitational forces. Bennu’s sampling experience shows that it is nearly impossible to predict how this pile of rubble will respond to the impact.
“The landing provided the first experience of pressing something to the surface,” Walsh said. “And if we ever go and really try to turn something like this, we’re going to need to know what the surface looks like so that it doesn’t just absorb the impact.”
Loretta added that the material underground appeared more red compared to Bennu’s bluish surface, suggesting that cosmic rays and other forms of space climate Erosion of exposed space rocks. Hues of red indicate that organic molecules, such as hydrocarbons, may be present inside the asteroid, which is of interest to researchers trying to understand the origins of life on Earth.
Scientists will have to wait until the scheduled delivery of OSIRIS-REx in September 2023 to obtain the precious materials. During the dramatic sampling attempt, Loretta said, the probe collected nearly 9 ounces (250 grams) of asteroid dust, which is somewhat less than the team had hoped for, but still four times what they needed to perform the analysis.
The OSIRIS-REx mission was recently extended and after the spacecraft drops its payload to Earth next year, He will go to ApophisIt is another very dangerous asteroid that it will visit in 2029.
The results are described in papers published Thursday (7 July) in the journals Sciences And the science progress.
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