Preparing for a black swan event

The success of NASA’s DART (Double Asteroid Redirection Test) mission which launched a 550-kg space vehicle to collide with an asteroid far away in space has given some confidence to the scientific community about working out a defence of the earth in the event of a large comet rushing towards it for a collision. The vehicle hit the asteroid moonlet, Dimorphos, orbiting a larger one, Didymos, last week but it is yet to be known whether it changed the flying rock’s trajectory. The mission was a proof of concept for a planetary defence system. The possibility of a large asteroid colliding with the earth and causing the extinction of life has been imagined and discussed for decades. It is believed that one such extinction happened over 65 million years ago when dinosaurs were wiped out. The NASA experiment was to test if humans could ward off such a threat to the earth and life on it.

Also Read | The Milky Way's spiral arms may have carved earth's continents

It was an unprecedented scientific challenge to tackle a fast-moving astronomical body the size of a football field 10.6 million km away. The spacecraft had to travel for 10 months through space and impact the asteroid at a pre-determined point of contact. Dimorphos was within visible range of the spacecraft just four hours before the moment of rendezvous and even had to do some course corrections in the end to hit the target. The impact was watched by many telescoping eyes in the sky and recorded. A year hence, another spacecraft will study in detail the consequences of the impact. There is a constant shower of meteors entering the earth’s atmosphere and the possibility of a large one crashing into it has been a nightmare. There is much more to learn if we have to avert that danger when it presents itself, and DART is a step in that direction. It also has military implications, especially in light of the possibility that future wars may be fought in space.

Imagination had soared into space where the ‘spaceship’ has now flown into and built-up scenarios of both doom and hope. It may be debated whether hitting the fleeting meteor was easier or more difficult than shooting an arrow at a tricky fish or into the eye of a fleeting bird in a shifting cage. But Hollywood thought up two disastrous scenarios in the films, Deep Impact and Armageddon, in which the nuclear bomb is used to save the earth from marauding comets. If DART shortened Dimorphos’ orbit by just about 10 minutes, we would know that we could sleep without a comet triggering a nightmare.