It’s the stuff of Hollywood movies, but the threat to Earth by hazardous asteroids is rooted in fact, not fiction.
“We look at the moon, we look at the Earth, we see that it’s full of craters. More on the Moon than on the Earth, which is, of course, telling us that impacts of small bodies on Earth on geologic time scales are normal,” says Thomas Zurbuchen, associate administrator for science at NASA.
If all goes well, the boxy, 1,200-pound craft will slam head-on into Dimorphos, an asteroid 525 feet (160 meters) across, at 15,000 mph next September.
“The DART spacecraft has to hit the asteroid, then DART has to measure the amount of deflection and then we want to understand why that deflection came about, how it works,” explains DART investigation team lead Andy Cheng.
“So, it’s all about measuring the momentum transfer. How much momentum do we put into the asteroid by hitting it with the DART spacecraft?”
Dimorphos orbits a much larger asteroid called Didymos.
The pair are no danger to Earth but offer scientists a better way to measure the effectiveness of a collision than a single asteroid flying through space.
Dimorphos completes one orbit of Didymos every 11 hours, 55 minutes. DART’s goal is a crash that will slow Dimorphos down and cause it to fall closer toward the bigger asteroid, shaving 10 minutes off its orbit.
The change in the orbital period will be measured by telescopes on Earth. The minimum change for the mission to be considered a success is 73 seconds.
“If we hit the asteroid period, just the dynamics involved will achieve the requirement that we change the asteroid by at least 73 seconds in its orbit period,” says DART project manager Ed Reynolds.
“We believe... and our simulations are showing much better than that. But we’re looking, if we hit the asteroid, we’re looking to change that orbit period by about 10 minutes.”
The DART technique could prove useful for altering the course of an asteroid years or decades before it bears down on Earth with the potential for catastrophe.
“In the quiver of all potential saving mechanisms, we’re trying to put some arrows there and this is, I think, the most potent one that we could think of right now,” says Zurbuchen.
Scientists constantly search for asteroids and plot their courses to determine whether they could hit the planet.
“It is absolutely true that at this moment in time, we are not aware of a threat in a hundred years,” says Zurbuchen.
“It’s also true that of all the bodies that are of the size that are going to bump into and bigger, we’ve only observed a third of them. And it’s frankly one of our tasks to observe the other two thirds in the next decade or so.”
DART will take 10 months to reach the asteroid pair. The collision will occur about 6.8 million miles from Earth.
Ten days beforehand, DART will release a tiny observation spacecraft supplied by the Italian space agency that will follow it.
DART will stream video until it is destroyed on impact. Three minutes later, the trailing craft will make images of the impact site and material that is ejected.
