A scenario worthy of Hollywood. The asteroid Dimorphos – hit by a NASA vessel to deviate its trajectory – will now be studied by the European Hera probe. Objective of this mission, which is scheduled to depart this Monday: to learn how to protect humanity from a possible future threat.
In 2022, the Dart mission ship deliberately crashed into the asteroid Dimorphos, the “Moon” of a larger asteroid named Didymos. This unique “planetary defense” test mission was to see if it was possible to deviate its trajectory, in the event that an asteroid one day threatened to hit the Earth. It is estimated that a one-kilometer object – triggering a global catastrophe like the extinction of the dinosaurs – crashes into Earth every 500,000 years, and a 140 m asteroid – the threshold for a regional catastrophe – every 20,000 years.
No direct threat
Among these near-Earth objects – most of which come from the asteroid belt between Mars and Jupiter – almost all those of one kilometer are known and none threaten the Earth in the coming century. No direct threat has been identified for those of 140 m either. But only 40% of them have been identified.
If it is therefore a natural risk “among the least probable”, we have “the advantage of being able to take actions to protect ourselves from it”, indicated during a press briefing, Patrick Michel, scientific manager of the Hera mission of the European Space Agency (ESA). Dimorphos, located some 11 million kilometers from Earth at the time of impact, measured approximately 160 m in diameter and posed no danger to our planet.
What impact on the asteroid?
By hitting it, the NASA device – the size of a large refrigerator – managed to move it by reducing its orbit by 33 minutes. But we don’t know what effects the impact had on the small asteroid, or even what its internal structure was before it. However, if the Dart experiment (Double Asteroid Redirection Test) made it possible to demonstrate the feasibility of the technique, we need to know more to validate it and be able to determine what energy would be necessary, if necessary, to effectively deflect a threatening asteroid.
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