Illustration of the Osiris-Rex sample return capsule passing through Earth’s atmosphere
NASA Goddard Space Flight Center/CI Lab
Fragments of asteroid Bennu return to Earth. NASA’s OSIRIS-REx spacecraft will collect samples from the asteroid in 2020 and is scheduled to arrive at Earth on September 24th.
Osiris-Rex was launched in 2016 and entered orbit around Bennu in 2018. Bennu was chosen as a target primarily because of its relatively short distance from Earth: at the time of launch it was approximately 225 million kilometers away, and over the intervening years, Bennu has become relatively close to Earth. Ta. It came close to 50 million kilometers from Earth.
Because of its regular close encounters, Bennu is considered a near-Earth object (NEO). It is not expected to collide with Earth any time soon, but there is about a 0.057% chance that it will occur within the next 300 years. Bennu is about 490 meters in diameter, so if it were to collide with Earth it would cause significant damage.
Finding ways to protect Earth from Bennu and asteroids like it is one reason to study it, but another is that it is one of the most primitive asteroids we know of. That is to say. “Asteroids like Bennu are time capsules from the early solar system, debris left over from the formation of the solar system,” he says. Anjani Pollitt University of Arizona, member of the OSIRIS-REx team.
Such asteroids likely aggregate to form the planets of our solar system, so they can be used to understand: How planets formed and grew. Bennu in particular has high concentrations of carbon, the main building block of organic molecules, which are the building blocks of life as we know it.
“We are confident that these samples contain organic molecules,” say OSIRIS-REx scientists Michelle Thompson at Purdue University in Indiana. “Studying these organic molecules may help us understand what organic matter was present in the early solar system that may have seeded life on Earth.”
Similar samples have already been returned from Japan’s Hayabusa2 spacecraft, which visited an asteroid called Ryugu. Comparing her two samples of asteroid dust will be a key element in the researchers’ goal of understanding the history of the solar system.
“If you were a visitor to Earth and you wanted to learn everything about Earth’s geological history, and you picked up a stone, you would never learn that,” Thompson says. . “Going to multiple asteroids opens up a whole new world and allows us to understand the diversity of matter from about 4.5 billion years ago,” around the time the solar system was forming.
The day starts early for the OSIRIS-REx team on September 24th. Early in the morning, the team’s engineers make a call about whether it is safe to release the sample capsule. When they say “go”, they will be hurtled toward Earth from a distance of about 102,000 kilometers, more than a quarter of the distance to the moon. It will fly for about four hours and enter the atmosphere at a speed of about 44,000 kilometers per hour. During the descent, he is protected and slowed by a heat shield and his two parachutes until he touches down in the Utah desert.
“Once we release the capsule, there’s nothing we can do except wait and hope everything goes well,” Pollitt said. “All of our years of research boiled down to that 13-minute descent into the atmosphere.” If the capsule can’t be released on September 24, it will be two years before there’s a chance to try again.
However, if released, the OSIRIS-REx spacecraft will continue on with an extended mission to the asteroid Apophis. On Earth, the sample will be immediately scooped up and sent to Houston, where scientists will begin analyzing it. “I honestly feel like a kid on Christmas Eve,” Thompson says. “I’m about to wake up and pick up all the sample gifts from Bennu.”
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