Sunday, December 5, 2021

NASA’s OSIRIS-REx departs asteroid Bennu with dust, rubble & a story of the solar system’s evolutionary history

On May 11, 2021, NASA’s OSIRIS REx spacecraft tucked rubble from asteroid Bennu, fired its engines and started its two-year-long journey back to earth. The robotic prospector, OSIRIS REx reached the near-Earth asteroid Bennu in October 2018, more than 200 million miles from Earth (321 million kilometres). It spent two years surveying the surface of the asteroid before collecting samples of rubbles from the surface last fall. The sample is collected from a site called Nightingale and will be delivered to Earth by September 2023.

Bringing samples home: Why is this mission so important?

The scientists from Arizona and NASA are responsible to build this spacecraft that has spent nearly two years observing, photographing and sampling the asteroid. Now, after flying around the asteroid for nearly two years, OSIRIS-REx has started its journey back to the Utah desert, carrying more than 60 grams of dust and fragments from the asteroid, the largest sample collected by NASA since the Apollo mission. According to the principal scientist of the University of Arizona, the rubble tucked inside NASA’s spacecraft will easily exceed the set target of at least 2 ounces (60 grams).

It is being counted as a major achievement as it will be the biggest cosmic haul for the U.S. since the Apollo moon rocks. While comet dust and solar wind samples have been returned to Earth in various missions conducted by NASA, this is the first time it’s gone after pieces of an asteroid. Japan has accomplished this kind of mission twice but in tiny amounts.

Things to know about Asteroid Bennu

As Bennu is a potentially hazardous asteroid that could be a threat to Earth one day, according to NASA, scientists and researchers are interested in studying this asteroid as it might give them clues about the origins of the solar system. Some of the interesting things to know about Asteroid Bennu are:

– It’s extremely dark: It is a B-type asteroid, which means it contains a lot of carbon along with other minerals. Considered to be an ancient asteroid, Bennu has not gone through any drastic, composition-altering change. This indicates that below its surface lie chemicals and rocks from the birth of the solar system. Bennu is like an artefact preserved in the vacuum of space, which is so old that it could uncover the secrets of the first life formed on Earth. This asteroid is hanging out with Earth for over a billion years, undisturbed. Apart from being close and carbonaceous, scientists have calculated that the asteroid Bennu was formed in the first 10 million years of our solar system’s history, which simply translates to over 4.5 billion years ago.

– Is Bennu space trash or scientific treasure?: Asteroid Bennu is a rubble pile, which means it is made from lots of pieces of rocky debris. This asteroid is as tall as the Empire State Building, with 20%-40% of its volume being empty space. This asteroid is classified as a threat to Earth because if it starts to rotate faster or interacts with a planetary body, it will shatter and fly apart.

Bennu: The name that finds its origin from an ancient Egyptian Deity

Bennu was named in 2013 and it is interesting to note that the name of the asteroid is given by a nine-year-old boy from North Carolina who won a competition ‘Name that Asteroid!’. This competition was conducted in collaboration with the LINEAR asteroid survey that discovered Bennu. The boy who won the competition suggested that the spacecraft’s Touch-and-Go Sample Mechanism (TAGSAM) resembles the neck and wings in illustrations of Bennu, whom ancient Egyptians usually depicted as a grey heron. Bennu is the ancient Egyptian deity who is linked with the Sun, creation and rebirth. The boy observed that the theme of the asteroid and the Egyptian deity sits well, as origin and rebirth are part of this asteroid’s story.

Observations about Bennu made by NASA so far

The spacecraft’s navigation camera observed that Bennu was spewing out streams of particles a couple of times each week. It is noted that this asteroid is a rare active asteroid in the handful of active asteroids identified so far. Through the navigation camera, it was observed that sunlight can crack rocks on Bennu and that it has pieces of another asteroid scattered across its surface. Upon sampling the piece of rubble when the spacecraft finally returns in the year 2023, the pieces of the puzzle will bring the whole story together – a story of the solar system’s evolutionary history.

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