Phew! Looks like we don’t need Superman after all. The earth can be saved.
Earthlings can now sleep easy, after the National Aeronautics and Space Agency (NASA) confirmed its first planetary defense test mission, called Double Asteroid Redirection Test (DART), was a success.
The ‘kinectic impactor’ programme involved the agency crashing a 600-kilo spacecraft into the asteroid Dimorphos on September 6 last year. Data now reveals that the impact altered the orbit of the asteroid moonlet by 33 minutes.
Nicola Fox, associate administrator for the Science Mission Directorate at NASA Headquarters, said: “I cheered when DART slammed head on into the asteroid for the world’s first planetary defense technology demonstration, and that was just the start. These findings add to our fundamental understanding of asteroids and build a foundation for how humanity can defend Earth from a potentially hazardous asteroid by altering its course.”
The success raises hope that a Chelyabinsk-like disaster can be prevented in the future. On 15 February 2013, an 18-meter superbolide (an extremely bright meteor) entered Earth’s atmosphere over southern Russia and exploded at a height of 29.7 kilometers.
The light from the meteor was briefly brighter than the Sun and visible from hundreds of kilometers away and when it burst, it sent tiny meteorites scattering through the sky. It was estimated that the explosion released nearly 30 times the energy of the atomic bomb dropped on Hiroshima. More than 1,500 people were injured, mostly from windows and doors being blown in buildings across six cities.
The Chelyabinsk incident was the wake-up call that accelerated the need for a planetary defence system.
At the time of launching the DART mission, NASA said they were looking at two outcomes from the kinetic impactor technique for it to be considered a potential tool of planetary defence – 1. that the spacecraft can be autonomously navigated and target an asteroid; and 2. that such an impact could change the asteroid’s orbit.
Scientists were expecting a change of around seven minutes in Dimorphos’ orbit, but the result far exceeded their expectations.
In her research paper, Cristina Thomas of Northern Arizona University, used two techniques for measurement and wrote: “A change in orbital period of approximately 7 minutes was expected if the incident momentum from the DART spacecraft was directly transferred to the asteroid target in a perfectly inelastic collision, but studies of the probable impact conditions and asteroid properties indicated that a considerable momentum enhancement was possible.
“In the years prior to impact, we used lightcurve observations to accurately determine the pre-impact orbit parameters of Dimorphos with respect to Didymos. Here we report the change in the orbital period of Dimorphos as a result of the DART kinetic impact to be -33.0 ±1.0 minutes.
“Using new Earth-based lightcurve and radar observations, two independent approaches determined identical values for the change in the orbital period.”
Thomas and her colleagues concluded: “To serve as a proof-of-concept for the kinetic impactor technique of planetary defense, DART needed to demonstrate that an asteroid could be targeted during a high-speed encounter and that the target’s orbit could be changed. DART has successfully done both.”
In another paper published in Nature, Terik Daly, Carolyn Ernst, and Olivier Barnouin of Johns Hopkins Applied Physics Laboratory (APL) reconstructed the entire timeline and process behind the impact and noted that DART’s successful autonomous targeting of a small asteroid, with limited prior observations, was critical in its future success.
Sufficient warning time, ranging from several years to preferably decades, was necessary for DART’s success, but the paper added: “Nevertheless, DART’s success builds optimism about humanity’s capacity to protect the Earth from an asteroid threat.”
A third paper validated the effectiveness of kinetic impact for preventing future asteroid strikes on the Earth.
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