For those who were around in 1998, you may remember that was the year that Hollywood decided the world was going to end with an asteroid hitting the earth. Movies like Armageddon and Deep Impact gave us different views of what how humanity might react to the impending doom of a giant asteroid headed our way. The concept goes back a lot further (at least to 1979 with Meteor), but one thing those 1998 movies had in common was humanity’s plan to address the crisis.
In each film, a variation on a plan of sending up a spaceship to detonate explosives on the asteroid was employed to at least some success. Thanks to Bruce Willis (Armageddon) and Robert Duvall (Deep Impact) humanity survived and the asteroid was at least partially diverted or destroyed before hitting the earth. Science fiction you say? Well, in a case of fiction mirroring reality, NASA recently launched the DART probe on Tuesday, November 23. It’s mission? Head a few million miles into outer space and smash head-on into an asteroid.
Dimorphos, your Days are Numbered
The DART probe is headed toward a pair of asteroids called Dimorphos and Didymos. Dimorphos is the smaller of the two and orbits the larger moonlet. Neither of these asteroids poses any threat to earth, however, they offer an opportunity to test the idea that if we hit an asteroid heading toward earth with enough force, we could knock it off course and force it to miss hitting the planet.
This test will involve what is called a Kinetic Impact. This means the entire goal is to simply slam the DART probe into Dimorphos and see if the impact itself is powerful enough to change the asteroid’s trajectory. DART weighs about 1,350 lbs and is basically a box measuring 3.9 x 4.3 x 4.3 feet. Dimorphos has a diameter of about 560 feet. So, this sounds a lot like throwing a pebble at a bowling ball and expecting the bowling ball to move, right?
Well, here’s the thing, by the time DART impacts Dimorphos, it will be traveling at roughly 15,000 miles per hour. Add that speed to DART’s mass and the expectations are that it will be enough to nudge the asteroid a measurable amount, which will be observed by how it continues to orbit its larger partner.
When Should you Make the Popcorn?
Sending a probe to intercept another moving object in space like this asteroid is a complicated process (i.e. it involves lots of math), to determine the correct course that will result in the to objects eventually meeting. Unlike in the disaster movies, this asteroid will be millions of miles away from the earth when DART reaches it, so it’s going to take some time. DART is also powered by an ion propulsion engine.
Without getting technical, ion propulsion starts very slowly and keeps adding speed incrementally over time. Think of it a bit like a 401K. You invest a small amount initially, but over time the growth accelerates, and hopefully by the time you retire you have a big nest egg. Fortunately, we don’t have to wait for our retirement for DART to reach its destination, but it won’t happen until later in 2022.
When the impact happens, DART will have released another small satellite that will record the action for posterity and send back what we hope will be some amazing footage of this sci-fi mission come to life.
