NASA is preparing a mission to deliberately smash a spacecraft into an asteroid a test run should humanity ever need to stop a giant space rock from wiping out life on Earth. NASA’s Planetary Defense Coordination Office is most interested in those larger than 460 feet in size, which have the potential to level entire cities or regions with many times the energy of average nuclear bombs.
There are 10,000 known near-Earth asteroids 460 feet in size or greater, but none has a significant chance to hit in the next 100 years. One major caveat: scientists think there are still 15,000 more such objects waiting to be discovered.
Scientists say the Didymos-Dimorphos system is an “ideal natural laboratory,” because Earth-based telescopes can easily measure the brightness variation of the pair and judge the time it takes the moonlet to orbit its big brother.
Since the current orbit period is known, the change will reveal the effect of the impact, scheduled to occur between September 26 and October 1, 2022.
The so-called “kinetic impactor” method isn’t the only way to divert an asteroid, but it is the only technique ready to deploy with current technology. Others that have been hypothesised include flying a spacecraft close by to impart a small gravitational force.
Another is detonating a nuclear blast close by — but not on the object itself, as in the films Armageddon and Deep Impact — which would probably create many more perilous objects. Scientists estimate 460-foot asteroids strike once every 20,000 years. Asteroids that are six miles or wider — such as the one that struck 66 million years ago and led to the extinction of most life on Earth, including the dinosaurs — occur around every 100-200 million years.