NASA’s OSIRIS-REx mission caused an unexpected explosion when it touched down on the asteroid Bennu to collect a valuable sample to be transported to Earth in October 2020.
Mission scientists describe the dramatic sampling that led to surprising discoveries about the asteroid’s nature in two new studies. And the results aren’t just intriguing: The researchers say the findings could have implications for a possible future drift mission if it’s 1,640 feet wide (500 meters). I (The most risky known near Earth asteroids) threatened to affect the planet.
“We expected the surface to be pretty rough, like when you touch a pile of gravel: some dust flies off and a few particles fly up,” said planetary scientist Dante Lauretta of the University of Arizona. OSIRIS-REx’s researcher told the mission Space.com.
“But we were stunned when we brought back the footage after the event,” he continued. “We saw a giant wall of debris flying from the sample side. It was really scary for spacecraft operators.”
Related: Asteroid Bennu’s mysterious lost craters suggest ‘impact armor’ protecting surface
The aftereffect was so unexpected that Lauretta, lead author of one of the two studies, campaigned for the spacecraft to revisit the area to find out what had happened. In April 2021, six months after sample collection, the researchers OSIRIS-REx touchdown site. When the spacecraft first arrived at Bennu, the site, called Nightingale, sat in a 65-foot-wide (20 m) impact crater. After landing, mission scientists found a brand new 26-foot-wide (8 m) void in which surface-displaced rubble and rocks were scattered around the site.
This is a surprisingly large scar; The scientists hoped to get a scoop as wide as the sample collector itself, as wide as 12 inches (30 centimeters). “But we sank,” Lauretta said. “There was clearly no resistance. The surface was soft and flowed like a liquid.”
The probe went as deep as 30 inches (70 cm) and revealed undisturbed material unlike the asteroid’s surface. cosmic rays and solar windstreams of high-energy particles from the sun.
From measurements obtained 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 metre), said Lauretta. For comparison, “a typical Soil “rock” has a density about six times higher, more like 190 pounds per cubic meter (3,000 kilograms).
A second study, based on measurements of the forces applied to the probe at impact, confirmed these numbers.
” [surface] The rocks are very porous and have a lot of space 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 adhere to the large rocks and fill the void and act as an adhesive to provide some strength, which will allow the surface to be pushed further back into the spacecraft. But it’s not there.”
Bennu’s soft, fluffy nature could make it difficult to attempt a possible future divergence if astronomers determine the rock’s threat to hit Earth. At 1,640 feet wide, an attack by Bennu causes continent-wide disruption to our planet. Although NASA estimates the probability of a collision 1 in 2,700 between 2175 and 2199Bennu is still one of the most dangerous asteroids currently known.
What’s more, scientists hypothesize that many asteroids have a similar “rubble pile” structure: essentially heaps of rock, gravel, and earth held together by weak gravitational forces. The sampling experiment at Bennu shows that it is nearly impossible to predict how such a pile of rubble would respond to an impact.
“The touchdown provided the first experience of actually pushing something to the surface,” Walsh said. Said. “And if we’re really trying to deflect something like this, we need to know what the surface is like so it doesn’t just absorb the impact.”
Lauretta added that the underground material appears more red compared to Bennu’s bluish surface. space weather erodes exposed space rocks. The reddish hues imply that organic molecules such as hydrocarbons may be present inside the asteroid, which is of great interest to researchers trying to understand the origins of life on Earth.
Scientists will have to wait until the planned delivery of OSIRIS-REx in September 2023 to obtain the valuable material. During the dramatic sampling attempt, the probe collected almost 9 ounces (250 grams) of asteroid dust, which was slightly less than the teams had hoped, but still four times more than they needed to run the analysis, Lauretta said.
The OSIRIS-REx mission has recently been extended, and after the spacecraft releases its payload to Earth next year, will go to ApophisAnother high-risk asteroid that it will visit in 2029.
The results are described in articles published in journals on Thursday, July 7. Science and Science Advances.
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