On Monday, September 26, 2022 NASA will intentionally crash one of its own spacecraft into an asteroid.
The first-ever mission to test technology for defending Earth against potential impacts by asteroids and comets, the ambitious Double Asteroid Redirection Test (DART) mission will actually impact Dimorphos, a small moonlet of the asteroid Didymos.
Didymos and Dimorphos are not on an Earth-bound trajectory, but they did get close to Earth in 2003 and it also occasionally gets close to Mars.
The landmark event will occur at exactly 7:14 pm EDT on Monday, September 26, 2022, with live coverage starting at 6:00 pm EDT on NASA TV on the agency’s website as well as on Facebook, Twitter and YouTube.
Here’s everything you need to know about the daring DART mission and what will happen after the impact:
What is DART?
It’s the first planetary defense mission. Its aim is to see if it’s possible to alter the trajectory of a potentially dangerous object in space by crashing into it. The aftermath of the kinetic impact by the 500 kg DART spacecraft on Dimorphos will be studied both immediately and over many years to see if it’s a workable solution for when a truly threatening object is headed our way.
What are Didymos and Dimorphos?
They’re two near-Earth asteroids that orbit each other, which is not unusual. The larger of the two bodies in this binary system is the 2,560 feet/780 meter diameter Didymos and the smaller 530 feet/160 meter Dimorphos (also called “Didymoon”), which orbits Didymos.
Didymos and Dimorphos have a two-year orbit of the Sun that’s slightly inclined to those of the planets and also slightly eccentric. They’re found just beyond Earth to just beyond Mars.
As DART reaches them Didymos and Dimorphos will be around 6.8 million miles/11 million kilometers away from Earth.
What will DART do?
The idea is that by creating a “kinetic deflection” on Dimorphos it will ever so slightly change the trajectory of both objects.
DART will crash into Dimorphos at about 15,000 miles per hour and, hopefully, change its orbital velocity by 0.4 mm/s, which will in turn slightly alter the trajectory of Didymos. If all goes to plan then the time it takes the smaller asteroid to orbit Didymos will shift by several minutes.
A simulation published in December 2021’s Icarus journal showed that DART “may excite” the spin of the Dimorphos moonlet and cause “chaotic tumbling” to achieve the hoped-for orbital change.
Will DART work?
The DART Investigation Team has highly detailed computer simulations of kinetic impacts on asteroids, but it has no direct evidence of what would actually happen. So a lot of time has been spent getting to know the binary asteroids in detail.
“The before-and-after nature of this experiment requires exquisite knowledge of the asteroid system before we do anything to it,” said Nick Moskovitz, an astronomer with Lowell Observatory in Flagstaff, Arizona and co-lead of an observation campaign conducted in July 2022. “We don’t want to, at the last minute, say, ‘Oh, here’s something we hadn’t thought about or phenomena we hadn’t considered.’ We want to be sure that any change we see is entirely due to what DART did.”
In October a bunch of ground-based telescopes around the world will be used to calculate Dimorphos’ new orbit. “Thanks to the worldwide effort of observing this system from ground-based telescopes, we know what it looks like before the impact,” said Moskovitz. “After impact, we will use some of the same techniques, to determine how much Dimorphos has moved and ultimately, how successful we were.”
However, another space agency is sending another spacecraft to double-check.
What is ‘Hera?’
The European Space Agency’s “Hera” follow-up mission—due to launch in 2024 and arrive in early January 2027—is an asteroid rendezvous spacecraft designed to go see if DART worked.
Hera will take a close look at both Didymos and Dimorphos using lasers, a star-tracker, a thermal infrared camera and accelerometers. It will see if the impact crater left by DART on Dimorphos (which it will get to within 200 meters of) has altered the trajectory of Didymos.
When did DART launch?
DART launched on Wednesday, November 24, 2021 from Vandenberg Space Force Base in California on a SpaceX Falcon 9 rocket. It had originally been planned to launch it on July 21, 2021, but was delayed due to COVID-19 supply chain issues and some technical challenges.
Wishing you clear skies and wide eyes.