An asteroid, also known as a minor planet, is a rocky celestial object that orbits the Sun, and is much smaller than a planet in size.
Bennu is a B-type asteroid, containing carbon and several other minerals in significant amounts.
Asteroid Bennu: In a historic event, NASA’s OSIRIS-REx spacecraft touched the surface of Asteroid Bennu on Tuesday in its first attempt to collect its sample. If all goes according to plan, the samples from Bennu’s surface would be delivered to Earth by 2023. The mission has been a very significant one. The asteroid was discovered in 1999 and it received its name in 2013, after a 9-year-old North Carolina boy won the “Name the Asteroid” contest by suggesting that it be named Bennu after an Egyptian deity, according to an IE report.
But why is NASA interested in studying this asteroid?
NASA’s asteroid sample collection: An asteroid explained
An asteroid, also known as a minor planet, is a rocky celestial object that orbits the Sun, and is much smaller than a planet in size. As per NASA, there are over 9.94 lakh known asteroids which are the remains from when the solar system formed over 4.6 billion years ago. The report added that there are three different classes of asteroids.
The first class of asteroids are those found in the main asteroid belt of the solar system. This asteroid belt is found between Mars and Jupiter. An estimated 1.1 million to 1.9 million asteroids are present in this belt.
The next class of asteroids is known as trojans, and they share their orbits with those of larger planets. According to NASA, there are Jupiter, Neptune, Mars and Earth trojans, with the Earth one having been reported in 2011.
The last class of asteroids is known as Near-Earth Asteroid (NEA) and the orbits of these asteroids pass by close to the Earth. Moreover, among the NEAs, the asteroids which have orbits crossing the Earth’s are known as Earth-crossers. At present, scientists are aware of over 10,000 such asteroids, and of them, more than 1,400 have been classified as potentially hazardous asteroids (PHA), which means that they pose a risk of collision with the Earth.
Why do scientists study asteroids and why Bennu?
Scientists study asteroids so they can find clues into how the solar system and the Sun formed, since the asteroids were also formed back then. Apart from that, their study is also important since some asteroids can be hazardous.
Bennu is an NEA, an Earth-crosser and a PHA, which is why it is important for scientists to gather information about it. It is roughly as tall as the Empire State Building and is 321 million kilometers away from the Earth. Apart from the fact that it could be hazardous and closer to the Earth, Bennu has also not undergone any significant changes since it was formed billions of years ago. Thus, it contains rocks as well as chemicals dating back to when the solar system was formed.
The OSIRIS-REx mission
OSIRIS-REx marks the first mission by NASA to collect and deliver to Earth samples from an ancient Asteroid. The US space agency aims to collect at least 60 grams of dust and rocks from the asteroid and bring them back. This, NASA claims, would be the largest amount of celestial material brought back to Earth since the Apollo era.
OSIRIS-REx was launched back in 2016, and it started orbiting Asteroid Bennu in December 2018. For the past two years, the spacecraft had been trying to match the asteroid’s velocity, while also studying and capturing images of its surface for potential landing sites and providing data for scientists to study how the Sun light has been affecting Bennu’s orbit. Any alteration in Bennu’s orbit could lead to a collision between the asteroid and the Earth, which is why this study is also significant.
The spacecraft, which in a touch-and-go mission landed on Bennu’s surface for five to 15 seconds, is fitted with cameras, a laser altimeter and a spectrometer, all to study the asteroid. If the spacecraft has been successful in collecting sufficient sample, then it would orbit the asteroid until a window for departure opens up next year. Otherwise, it would go in for another sample collection attempt in January 2021.
Once OSIRIS-REx departs Bennu’s orbit, it will take two years before it successfully reaches the Earth.
Why are chemicals and rocks from asteroids important?
Considering the fact that Bennu has existed since the solar system, there is a high probability that its material has molecules which were present even back when life began on Earth. Carbon atom chains form the basis of life on Earth, the report states. According to NASA, the organic material which scientists are hoping to find in the sample from Bennu does not come from Biology necessarily, but it could help them in further understanding how asteroids rich in organic material helped catalyse life on Earth.
Asteroid Bennu: What we know so far
Bennu is a B-type asteroid, containing carbon and several other minerals in significant amounts. Due to the high carbon content, Bennu is able to reflect about 4% of the Sun light it receives, much less than a planet like Venus with 65% reflection. Earth reflects 30% of the Sunlight it receives. Moreover, about 20% to 40% of the interior of the asteroid is empty space. As per scientists, Bennu was formed about 4.5 years ago, within the first 10 million years of the formation of our solar system.
Moreover, the high quality images of the asteroid transmitted to scientists by OSIRIS-REx show that the asteroid’s surface contains rocky boulders, much in contrast to scientists’ earlier belief that it had a sandy surface. This terrain has made it more difficult to collect sample from the asteroid. Moreover, there is a chance that Bennu could collide with Earth about 150 years later.