DART Smashes Into an Asteroid, as Planned

DART Smashes Into an Asteroid, as Planned

A spacecraft smashed into an asteroid this evening. No worries, that’s what it was supposed to do. NASA’s Double Asteroid Redirection Test, or DART, tested whether the kinetic energy imparted during a collision could change an asteroid’s orbit. This asteroid, Dimorphos, the tiny moon of another asteroid, Didymos, poses no threat to Earth, but asteroids have plagued our planet in the past and this could be a method for deflecting them in the future.

DART was launched last November with the singular task of ramming itself into the 525-foot diameter asteroid Dimorphos, one of two bodies in a binary asteroid system. Dimorphos orbits the larger asteroid, Didymos, which itself is just half-a-mile in diameter.

Located 7 million miles from Earth, they were discovered in 1996, but are so small that little was known about them until tonight. The surface of Dimorphos, in particular, was a mystery until DART’s DRACO camera caught it in the crosshairs moments before impact at 7:14 pm ET.

Basically it looks like a rubble pile.

Dimorphos, seconds before impact. Screengrab.
One of the very last images of Dimorphos moments before impact. Screengrab.


DART was controlled by the Mission Operations Center at Johns Hopkins Applied Physics Laboratory (APL) in Laurel, MD, which manages the mission for NASA. APL’s Small-body Maneuvering Autonomous Real Time Navigation or SMART Nav system guided the spacecraft to its date with destiny. For the last four hours of the journey, SMART Nav was completely in control as DART approached Dimorphos at 13,421 miles per hour.

So the first part of the mission, impacting Dimorphos, is a complete success. The second part is determining how much Dimorphos’s orbit changed, which will inform any future efforts to deflect asteroids that threaten Earth.

Dozens of ground-based telescopes and radars around the world are fixed on Dimorphos to calculate that answer. Its orbit around Didymos has been 11 hours and 55 minutes until now. Scientists expect it may change by as many as 10 minutes, but it will take some time to get a definitive answer.

Tom Statler, DART Program Scientist at NASA, said last week he “would be surprised if we had a firm measurement of the period change in less than a few days and I would be really surprised if it took more than three weeks.” During a post-impact press conference this evening, DART Mission System Engineer Elena Adams said “confirmation of the exact period change” could take a “couple of months” even though pieces of the answer may be known sooner.

Scientists also are eager to see the impact crater. The first images should come from the Light Italian CubeSat for Imaging of Asteroids (LICIACube) provided by the Italian Space Agency. It launched together with DART and separated 15 days ago so it could take images as the spacecraft met its fate. NASA said the images will be “downlinked to Earth one by one in the coming weeks.” The first could arrive in hours.

Three spacecraft also are taking a look. Though they could not see the impact, they might be able to detect changes in brightness from the ejecta spewed into space: the Hubble Space Telescope in Earth orbit, the James Webb Space Telescope at the Sun-Earth Lagrange Point-2 a million miles from Earth, and the Lucy spacecraft on its way to the Trojan asteroids. Lucy is currently about 6.5 million miles from Earth and only half a million miles from Didymos and Dimorphos.

ESA’s Hera spacecraft will provide even more data when it arrives there in 2026. DART and Hera are part of a NASA-ESA joint effort called the Asteroid Impact and Deflection Assessment (AIDA).

In an interview on NASA’s DART broadcast, Lori Glaze, Director of NASA’s Planetary Science Division, enthused that “we’re embarking on a new era of humankind, an era in which we potentially have the capability to protect ourselves from something like a dangerous hazardous asteroid impact. What an amazing thing. We’ve never had that capability before.”

NASA’s Planetary Defense Officer, Lindley Johnson, said “DART’s success provides a significant addition to the essential toolbox we must have to protect Earth from a devastating impact by an asteroid. This demonstrates we are no longer powerless to prevent this type of natural disaster.”

Rep. Don Beyer (D-VA), chair of the space subcommittee of the House Science, Space, and Technology Committee, said tonight he is “excited about DART’s historic success today.”

“This mission represents the forward-thinking of NASA and its partners on a key capability for our planetary defense. While the likelihood of an asteroid impact to Earth is low, the potential damage of an impact could be devastating. DART’s successful test gives us a demonstrated technique for how we might nudge off course a potentially hazardous asteroid headed for Earth. I look forward to learning more about the results of DART’s pioneering test.”

Beyer’s committee has a long-standing interest in defending Earth from asteroids and comets — Near Earth Objects (NEOs). In 1998, it led the effort to direct NASA to locate 90 percent of hazardous asteroids 1-kilometer (0.6 miles) or more in diameter within 10 years. That size asteroid is thought to have caused the extinction of the dinosaurs. NASA accomplished that task and in 2005 Congress set another goal of locating 90 percent of hazardous asteroids 140-meters (460 feet) or more in diameter within 15 years in the George E. Brown Near-Earth Object Survey Act, part of the 2005 NASA Authorization Act. Brown was a former chairman of the committee and deeply interested in NEOs.

The 15 years have elapsed and while progress has been made, there is a long way to go because it is difficult to find such small, dark objects using only ground-based telescopes.

Johnson leads NASA’s Planetary Defense Coordination Office (PDCO). Its next mission is NEO Surveyor, a space-based infrared telescope designed specifically to locate NEOs. NASA proposed delaying NEO Surveyor by two years, from 2026 to 2028, in its FY2023 budget request currently being debated by Congress. House and Senate appropriators urged NASA to keep the launch date in 2026 or at least launch it before 2028 and added money to that end, though what will be in the final appropriations bill is yet to be determined.

NEO Surveyor is going through its Preliminary Design Review this week. The University of Arizona’s Amy Mainzer, Survey Director for NEO Surveyor, estimates it will take 10 more years to fulfill the congressional requirement once NEO Surveyor is in orbit. Without NEO Surveyor, make that 30 years.

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