The NASA spacecraft OSIRIS-REx is delivering the space capsule containing the sample collected from the near-earth asteroid 101955 Bennu. The OSIRIS-REx was launched on 08 September in the year 2016. The spacecraft will drop the capsule into the Earth from a distance of 1,01,388 kilo meters. On 24 September 2023, the capsule will land on a facility in Utah, from where it will be collected for analysis and research.
An asteroid is a small planet that orbits around the Sun. Asteroids vary in their diameter from 10 meters to ~1000 miles. The largest known asteroid 1 Ceres with a designated number 1 has a diameter of 939 kilometres. The gravity of the asteroids is very less compared to main planets and their moons. Bennu is one of the near-earth asteroid orbiting the Sun with a maximum distance of 350 million kilometres to Earth. Bennu is an earth-crossing asteroid meaning, the asteroid orbit and orbit of the Earth intersect at a specific distance. As per scientists, Bennu has a chance of 1 in 2700 to collide with Earth during the later part of 22nd century. Bennu is a C-Type asteroid that contains lot of Carbon in its composition. Bennu is a collection of rocks, boulders, gravel and dust pulled together through a weak gravity which is orbiting the Sun.
As per NASA the OSIRIS-REX has collected around 250 grams of sample from the surface asteroid Bennu. The sample collection itself was an interesting task as the spacecraft punched the surface with very little velocity of 10 centimetre/second which resulted in a huge amount of boulders, rock and dust raising for several meters of height. What scientists believed was, the surface of the Bennu and its underneath to exhibit cohesive behaviour. But the material on the surface was not cohesive as expected. It was just loose like a plastic ball-pit as the gravity was far too less(when compared to bigger celestial bodies like Earth and the moon). Remember, the combined mass of all the asteroids of the solar families put together is only a fraction of our Moon.
Research about asteroids is to understand the origins of life and to know more about the dynamics of these asteroids. Understanding the dynamics of the asteroids will help humanity by preventing the asteroids from colliding into Earth. The research on asteroids has also found that some of these asteroids has enormous amounts of precious metals and other useful minerals and compounds. As stated by NASA, the recent understanding of the surface of the asteroid during the sample collection from Bennu also suggests that even if the asteroid Bennu collides with Earth one day, the impact will be of different nature than a collision of a monolith”.
Earlier in the year 2014 the Japanese Space Agency JAXA has sent a spacecraft Hayabusa2 to the near-earth asteroid Ryugu, which is also a Type-C asteroid. JAXA has shared a portion of the sample collected from Ryugu with NASA. Similarly NASA is sharing a portion of the sample collected from the asteroid Bennu with Japan. The precursor to Hayabusa2 was the Hayabusa mission that was launched on 2003, which is the first sample-return mission.
After delivering the sample to Earth the OSIRIS-REx will conitnue its journey in space with new objective - to study the asteroid Apophis. Unlike Ryugu and Bennu, Apophis is an S-Type asteroid mostly made of silicates and metals like nickel and iron. The Apophis is also a near-earth object and an earth-crossing asteroid. Hence it becomes all the more important to study a stony asteroid which is also an earth-crosser in detail. For that we need to wait at least till 2029 on which year the asteroid will pass within 31860 kilometres from Earth.
* Unless specifically stated, Moon refers to the moon of our mother Earth