Scientists have calculated the exact date when an asteroid named Bennu could collide with Earth with a force equivalent to 22 atomic bombs. The space rock, which is about the size of the Empire State Building, orbits the Sun every six years and has a one in 2,700 chance of hitting our planet on September 24, 2182. NASA is working on a plan to divert Bennu and prevent a possible catastrophe.
Bennu: A potential threat to Earth
Bennu is one of the most hazardous asteroids known to humanity, as it has a relatively high probability of impacting Earth in the next two centuries. According to NASA, if Bennu were to hit Earth, it would create a crater about six miles wide and release more than 1,200 megatons of energy. That is more than 80 times the energy of the atomic bomb dropped on Hiroshima in 1945.
Bennu was discovered in 1999 by the Lincoln Near-Earth Asteroid Research (LINEAR) project. It is classified as a near-Earth object (NEO), which means it has an orbit that brings it within 30 million miles of Earth’s orbit. Bennu is also a potentially hazardous object (PHO), which means it has an orbit that brings it within 4.6 million miles of Earth and has a diameter larger than 500 feet.
Bennu belongs to a group of asteroids called B-type, which are rich in carbon and contain organic molecules, water, and minerals. Scientists believe that these asteroids may have delivered the building blocks of life to Earth billions of years ago.
OSIRIS-REx: A mission to study and sample Bennu
In 2016, NASA launched the Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) mission to study and sample Bennu. The spacecraft arrived at Bennu in 2018 and spent two years mapping its surface, measuring its shape, mass, density, rotation, and gravity. In October 2020, OSIRIS-REx performed a daring maneuver called Touch-And-Go (TAG), in which it briefly touched the asteroid and collected about two ounces of dust and rocks.
OSIRIS-REx is now on its way back to Earth with the precious cargo. It is expected to reach our planet on September 24, 2023, exactly 159 years before the potential impact date. The spacecraft will release a capsule containing the samples, which will parachute down to the Utah Test and Training Range. Scientists hope that by analyzing the material from Bennu, they will learn more about the origin and evolution of our solar system and the origin of life on Earth.
DART: A plan to deflect Bennu
While OSIRIS-REx is returning home, NASA is preparing another mission to deal with Bennu’s threat. The Double Asteroid Redirection Test (DART) is a demonstration of a technique called kinetic impactor, which involves crashing a spacecraft into an asteroid at high speed to change its orbit.
DART will target a smaller asteroid called Dimorphos, which orbits a larger asteroid called Didymos. Both asteroids are NEOs but pose no danger to Earth. DART will launch in November 2021 and reach Didymos in September 2022. It will then collide with Dimorphos at about 15,000 miles per hour, creating a crater and altering its velocity by a fraction of an inch per second.
The impact will be observed by telescopes on Earth and by a small Italian spacecraft called LICIACube, which will accompany DART. Scientists will measure how much Dimorphos’ orbit changes as a result of the collision. This will help them estimate how effective the kinetic impactor technique would be for deflecting larger asteroids like Bennu in the future.
Asteroid defense: A global challenge
Bennu is not the only asteroid that could pose a risk to Earth. There are more than 26,000 NEOs that have been detected so far, and about 2,000 of them are PHOs. NASA estimates that there are still tens of thousands of NEOs that have not been discovered yet.
To protect our planet from potential impacts, NASA and other space agencies around the world are working together to monitor and track NEOs, characterize their physical properties and orbits, and develop mitigation strategies. NASA also conducts regular exercises with other government agencies and international partners to simulate asteroid impact scenarios and test response plans.
Asteroid defense is a global challenge that requires international cooperation and coordination. As Rich Burns, project manager for OSIRIS-REx at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said: “We are not alone in our efforts to understand and address the hazards posed by asteroids. OSIRIS-REx is part of a larger, global community of scientists, engineers, policymakers, and citizens who are working together to ensure the safety of our planet from these natural threats.”
