The Era of Planetary Defense Has Begun

In Modern Principles of Economics, Tyler and I use asteroid defense as an example of a public good (see video below). As of the 5th edition, this public good wasn’t being provided by either markets or governments. But thanks to NASA, the era of planetary defense has begun. In September of 2022 NASA smashed a spacecraft into an asteroid. A new set of five papers in Nature has now demonstrated that not only did NASA hit its target, the mission was a success in diverting the asteroid:

DART, which was the size of a golf cart, collided with a Great Pyramid-sized asteroid called Dimorphos. The impact caused the asteroid’s orbit around another space rock to shrink — Dimorphos now completes an orbit 33 minutes faster than before the impact, researchers report1 today in Nature.

…As DART hurtled towards Dimorphos at more than 6 kilometres per second, the first part that hit was one of its solar panels, which smashed into a 6.5-metre-wide boulder. Microseconds later, the main body of the spacecraft collided with the rocky surface next to the boulder — and the US$330-million DART shattered to bits….the spacecraft hit a spot around 25 metres from the asteroid’s centre, maximizing the force of its impact….large amounts of the asteroid’s rubble flew outwards from the impact. The recoil from this force pushed the asteroid further off its previous trajectory. Researchers estimate that this spray of rubble meant Dimorphos’ added momentum was almost four times that imparted by DART.

…Although NASA has demonstrated this technique on only one asteroid, the results could be broadly applicable to future hazards…if a dangerous asteroid were ever detected heading for Earth, a mission to smash into it would probably be able to divert it away from the planet.



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