Last month, the European Space Agency launched one of the most important space missions in history. You’ve probably never heard of it.
Hera is the follow-up mission to NASA’s DART mission, which was an insanely successful mission that aimed – literally – at a very difficult goal: hitting an asteroid with a projectile from Earth and changing its motion.
On Sept. 22, 2022, DART, which had launched 10 months earlier, successfully whacked into an asteroid called Dimorphos, which was in orbit around a larger asteroid called Didymos.
DART, which stands for Double Asteroid Redirection Test, had to be carefully planned and programmed. When the impact happened, it was more than 11 million kilometres away from Earth, which means radio messages would have taken more than half an hour to travel to and from the satellite.
But everything worked!
DART slammed into Dimorphos, and observations confirmed the impact changed its orbit, as well as making a big crater. Now the ESA Hera project will come in for a closer look to see exactly how DART fared.
Why are NASA and the ESA spending millions of dollars to smash space probes into distant floating rocks?
It’s our first attempt at creating a system to ward off any chance that one of those rocks tumbles down towards us and lands on, say, a major city. Because a random asteroid could wipe out Winnipeg or Vienna or Seoul. And a slightly bigger random asteroid could wipe out all of humanity.
We know this because we have a pretty good handle on what killed the dinosaurs a little more than 66 million years ago.
A 10-km wide asteroid fell out of space and smashed into what is now the Yucatan Peninsula and the Gulf of Mexico. It left a crater 200-km wide. One of the ways we know how bad it was is because we have evidence that it literally rained molten glass over a fairly wide area. Not something you want to see in the forecast.
The Chicxulub impactor caused a massive shockwave, then it rained fire, and then all the water vapour it had thrown into the atmosphere caused a years-long nuclear winter that killed a good percentage of Earth’s vegetation.
Most of the species then on the earth, including all dinosaurs except birds, went extinct.
But even a much smaller asteroid could really mess up our day.
Look at the 1908 Tunguska event, in which an asteroid estimated at 50-60 metres wide slammed into the atmosphere above a remote region of Siberia, where it exploded. The airburst created a shockwave that knocked down 80 million trees over 2,100 square miles.
There are a lot of rocks in space, most of them floating millions of miles away, on orbits that will never meet Earth’s. But every once in a while, one of them gets knocked out of its track, and the sun’s gravity sends it rolling towards the inner solar system, where we live.
It would be better, in general, if we had a plan for how to deal with the next unwelcome guest before it arrives in our upper atmosphere.
