Can humanity be saved by a nudge rather than a bang if an asteroid is hurtling toward Earth?
NASA is planning a first-of-its-kind mission to deflect an asteroid by intentionally crashing a spacecraft into it. The mission provides a once-in-a-lifetime opportunity to put to the test a planetary defense strategy that could protect Earth from a potentially catastrophic collision in the future.
The $325 million DART mission, which stands for Double Asteroid Redirection Test, lifted off from Vandenberg Air Force Base in California at 1:21 a.m. ET on Wednesday. The spacecraft was launched into orbit by a SpaceX Falcon 9 rocket.
The probe will travel for nearly a year to an asteroid system more than 6.5 million miles away from Earth. The mission’s target is Dimorphos, a 525-foot-wide space rock that orbits Didymos, a much larger asteroid that measures around 2,500 feet across. According to NASA, neither Dimorphos nor Didymos pose a threat to Earth, but the system is a “perfect testing ground” for whether crashing a spacecraft into an asteroid can effectively change its motion in space.
NASA’s DART spacecraft will collide with Dimorphos at a speed of around 15,000 mph next fall. For decades, Earth-based telescopes have studied Didymos and its “moonlet” Dimorphos, observing that the smaller space rock circles its larger counterpart once every 11 hours and 55 minutes, according to Nancy Chabot, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory and the mission’s coordination lead.
Chabot and her colleagues want to see if Dimorphos’ nearly 12-hour orbit can be altered by the cosmic collision. According to NASA, the maneuver will only change the speed of the space rock’s orbit by a fraction of a percent — a difference of only several minutes — but the shift should be detectable by ground-based telescopes.
“This isn’t going to destroy the asteroid; it’s just going to give it a small nudge,” she said earlier this month during a press conference. “It will actually deflect its path around the larger asteroid, so we’ll be demonstrating asteroid deflection in this double asteroid system.”
The DART probe will be destroyed in the test, but a small, Italian-built cubesat that the spacecraft will deploy more than a week before the crash will transmit images of the impact and its aftermath.
A follow-up mission developed by the European Space Agency will investigate the Didymos system in greater detail and assess the outcome of the DART probe’s deflection. Hera, the mission, is scheduled to launch in October 2024. According to NASA, no known asteroid larger than 450 feet has a significant chance of colliding with the planet in the next 100 years, but only a small number of smaller near-Earth objects have been discovered so far.
The Planetary Defense Coordination Office of the agency is tasked with searching for near-Earth objects that are potentially hazardous to the planet, such as those that travel within 5 million miles of Earth’s orbit and objects large enough to cause significant damage if they impact the planet’s surface.
If a large space rock is discovered on a collision course with Earth in the future, tests like the DART mission could assist NASA in responding to the threat.
“It’s very rare for an asteroid to strike the Earth,” said Lindley Johnson, a planetary defense officer at NASA Headquarters in Washington, D.C., “but it’s something we want to be aware of well in advance.”
