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Recently, NASA’s OSIRIS-REx — Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer — spacecraft briefly touched asteroid Bennu, from where it is meant to collect samples of dust and pebbles and deliver them back to Earth in 2023.
What is an asteroid?
- Asteroids are rocky objects that orbit the Sun, much smaller than planets. They are also called minor planets.
- Asteroids are divided into three classes. First, those found in the main asteroid belt between Mars and Jupiter, which is estimated to contain somewhere between 1.1-1.9 million asteroids.
- The second group is that of trojans, which are asteroids that share an orbit with a larger planet. NASA reports the presence of Jupiter, Neptune and Mars trojans. In 2011, they reported an Earth trojan as well.
- The third classification is Near-Earth Asteroids (NEA), which have orbits that pass close by the Earth. Those that cross the Earth’s orbit are called Earth-crossers. More than 10,000 such asteroids are known, out of which over 1,400 are classified as potentially hazardous asteroids (PHAs).
What is the OSIRIS-REx mission?
- This is NASA’s first mission meant to return a sample from the ancient asteroid. The mission is essentially a seven-year-long voyage and will conclude when at least 60 grams of samples are delivered back to the Earth.
- The mission was launched in 2016, it reached its target in 2018 and since then, the spacecraft has been trying to match the velocity of the asteroid using small rocket thrusters to rendezvous it.
- It also utilised this time to survey the surface and identify potential sites to take samples.
About Bennu Asteroid
- Bennu is an asteroid about as tall as the Empire State Building and located at a distance of about 200 million miles away from the Earth.
- There is a slight possibility that Bennu, which is classified as a Near Earth Object (NEO), might strike the Earth in the next century, between the years 2175 and 2199. NEOs are comets and asteroids nudged by the gravitational attraction of nearby planets into orbits which allows them to enter the Earth’s neighbourhood.
- Scientists study asteroids to look for information about the formation and history of planets and the Sun since asteroids were formed at the same time as other objects in the solar system. Another reason for tracking them is to look for asteroids that might be potentially hazardous.
Important terminological differences
- Comet: A body of ice, rock, and dust that can be several miles in diameter and orbits the sun. Debris from comets is the source of many meteoroids.
- Meteoroid: A small rocky or metal object, usually between the size of a grain of sand or a boulder, that orbits the sun. It originates from a comet or asteroid.
- Meteor: A meteoroid that enters the earth’s atmosphere and vaporises. Also called a “shooting star.”
- Meteorite: A meteor that hits Earth without burning up in the atmosphere i.e. it reaches the Earth’s surface.
- Meteor shower: A collection of meteors visible when Earth passes through a trail of debris left by a comet.
- Asteroid: An object larger than a meteoroid that orbits the sun and is made of rock or metal. Historically, objects larger than 10 meters across have been called asteroids.