In the vacuum of space, there is darkness. There is light. And there are asteroids.
What started as a loud, fiery launch from Vandenberg Space Force Base on November 24, 2021, the DART (Double Asteroid Redirection Test) spacecraft purposely ended it’s life on September 26, 2022.
The little spacecraft had a one way ticket to Dimorphos, slamming itself into the asteroid at 14,000 miles per hour.
In Earth’s first ever planetary defense test mission, NASA and Johns Hopkins Applied Physics Laboratory (APL) were successful with what they set out to do.
They changed the trajectory of an asteroid using kinetic impact.
It’s not just a Hollywood movie script anymore.
Armageddon. Deep Impact. Don’t Look Up.
Hollywood has certainly tantalized our senses and our fears with movies about asteroids and comets hitting our planet: oil drillers saving the world, a bomb splitting a comet in two, ignoring the inevitable.
Could any of these scenarios become a reality?
On February 15, 2013, a meteor exploded over Chelyabinsk, Russia. The explosion created an airburst and shockwave that struck six cities across the country. That asteroid was only 60-feet wide but weighed 10,000 metric tons. Astronomers have estimated that there are tens of thousands of asteroids near our planet that are 500 feet wide and larger. These are big enough to completely destroy much of our planet if we were to take a direct hit.
How can we deflect an asteroid without further endangering our planet?
One of the core missions of the DART spacecraft was to test kinetic impact. Could a spacecraft the approximate size of a large van, weighing about 1,260 pounds and moving at 3.8 miles per second at impact move an asteroid that was about 530 feet wide?
Dimorphos was the perfect candidate to test this theory.
Asteroid Didymos (bottom left) and its moonlet, Dimorphos, about 2.5 minutes before DART impacted Dimorphos at 7:14 p.m. EDT on Sept. 26, 2022. The image was taken by DART’s DRACO imager from a distance of 570 miles (920 kilometers). Photo Credit: NASA/Johns Hopkins APL
An asteroid orbiting another asteroid.
Asteroid Didymos and its small moonlet Dimorphos make up what’s called a binary asteroid system. This means the small moon Dimorphos orbits the larger body Didymos.
Neither Didymos nor Dimorphos would ever hit Earth, but their “close” proximity to Earth (and by close, I mean approximately 7 million miles) made them ideal candidates for testing kinetic impact.
NASA and APL wanted to see if DART would alter the Dimorphos’ orbit around Didymos.
Before impact, it took Dimorphos 11 hours and 55 minutes to orbit Didymos.
And then DART said hello to Didymos. And ultimately goodbye to us.
When DART hit Dimorphos, telescopes and cameras in space and on Earth were there to capture the impact.
And it was spectacular.
This is the last complete image of the asteroid Dimorphos, as seen by our DART two seconds before impact. The Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO) imager aboard captured a 100-foot-wide patch of the asteroid. The DART spacecraft streamed these images from its DRACO camera back to Earth in real time as it approached the asteroid. Photo Credit: NASA/Johns Hopkins APLImage captured by the Italian Space Agency’s LICIACube a few minutes after the intentional collision of NASA’s DART mission with its target asteroid, Dimorphos, captured on Sept. 26, 2022. Photo Credits: ASI/NASAImage captured by the Italian Space Agency’s LICIACube a few minutes after the intentional collision of NASA’s DART mission with its target asteroid, Dimorphos, captured on Sept. 26, 2022. Photo Credits: ASI/NASAThese images from NASA’s Hubble Space Telescope, taken (left to right) 22 minutes, 5 hours, and 8.2 hours after NASA’s DART intentionally impacted Dimorphos, show expanding plumes of ejecta from the asteroid’s body. The Hubble images show ejecta from the impact that appear as rays stretching out from the body of the asteroid. The bolder, fanned-out spike of ejecta to the left of the asteroid is in the general direction from which DART approached. These observations, when combined with data from NASA’s James Webb Space Telescope, will allow scientists to gain knowledge about the nature of the surface of Dimorphos, how much material was ejected by the collision, how fast it was ejected, and the distribution of particle sizes in the expanding dust cloud. Photo Credits: Science: NASA, ESA, Jian-Yang Li (PSI); image processing: Alyssa Pagan (STScI)This image from NASA’s James Webb Space Telescope’s Near-Infrared Camera (NIRCam) instrument shows Dimorphos about 4 hours after NASA’s DART made impact. A tight, compact core and plumes of material appearing as wisps streaming away from the center of where the impact took place, are visible in the image. Those sharp points are Webb’s distinctive eight diffraction spikes, an artifact of the telescope’s structure. Photo Credit: NASA, ESA, CSA, Cristina Thomas (Northern Arizona University), Ian Wong (NASA-GSFC) IMAGE PROCESSING: Joseph DePasquale (STScI)This imagery from NASA’s Hubble Space Telescope from Oct. 8, 2022, shows the debris blasted from the surface of Dimorphos 285 hours after the asteroid was intentionally impacted by NASA’s DART. The shape of that tail has changed over time. Scientists are continuing to study this material and how it moves in space, in order to better understand the asteroid. Photo Credits: NASA/ESA/STScI/HubbleImages taken at ATLAS every 40 seconds from the time of impact show the plume of dust after the collision. Credit: ATLAS South Africa Telescope
Did kinetic impact work?
The news we were all eagerly waiting to hear was recently announced at a NASA press conference.
Astronomers using telescopes on Earth have measured that DART’s impact altered Dimorphos’ orbit around Didymos by 32 minutes – shortening it from 11 hours and 55 minutes to 11 hours and 23 minutes. This surpassed NASA’s benchmark by more than 25 times.
This animation shows a highly magnified view of how Dimorphos’ orbit around Didymos is seen from Earth, approximately one week after the DART impact. Each time around the orbit, Dimorphos passes through the shadow cast by Didymos, and half an orbit later, briefly casts a shadow onto Didymos. In reality, only the combined light from both asteroids can be seen by telescopes. The graph shows how the total brightness dips slightly when either body is shadowed by the other. DART astronomers measure the time intervals between the dips that mark these eclipse events in order to determine the new period of the orbit. Credits: NASA/APL/UMD
The investigation doesn’t end there.
Scientists are focusing on measuring the efficiency of momentum transfer from DART’s 14,000 mile per hour collision with Dimorphos. They are analyzing the ejected material – that long plume of asteroidal rock displaced and launched into space by the impact. That recoil from the blast of debris enhanced DART’s push on Dimorphos. Scientists want to look at the asteroid’s physical properties, such as the character of its surface, especially how strong or weak it was.
This successful test and all of these observations will make a big difference next time….when we need to do this for real.
