NASA is going to ram a moon in September – and that could have much bigger consequences than expected

The US space agency expects to create a small crater, but new research suggests it will change the moon beyond recognition.

The DART spacecraft was launched last November. And this mission has a special purpose. The spacecraft will set course for the asteroid Didymos and ram its moon, in an attempt to change its orbit. NASA hoped to give the moon just “a little push.” But new simulations show that DART may hit the moon much harder than intended.

The DART space probe (Double Asteroid Redirection Test) has been en route to asteroid Didymos for about seven months. Didymos (Greek for twins) is a binary system that consists of two parts. Didymos A has a diameter of 780 meters. Around Didymos A, a smaller celestial body of about 160 meters orbits. This moon, called Dimorphos, completes one orbit every 11 hours and 55 minutes.

change job

The intention is for the DART spacecraft to deliberately smash itself into the small moon, altering the orbit of Dimorphos. And because Dimorphos is part of a binary system, it’s relatively easy to calculate the modified trajectory after DART hits it. Scientists hope to learn more about whether such a technique, in which the direction of a space rock is deflected by an impact, is a working strategy. In this way, space rocks on a collision course with Earth could potentially be averted in the future. In short, the mission will help us better understand how to protect our precious planet from potentially dangerous future nearers.

small crater

So the idea is that the DART spacecraft is going to ram the moon Dimorphos. And at more than 6 km/sec (about nine times faster than a bullet). Incidentally, Dimorphos is not supposed to be completely blown up; the American space agency only expects to create a small crater. The researchers hope that the impact will only slightly alter the moon’s orbit.

New simulations

New simulations, published in The Planetary Science Journal, however, now suggest that the consequences could be much greater. “Contrary to what one might imagine for an asteroid, direct evidence from the Japanese space mission Hayabusa2, among others, shows that asteroids have a very loose, internal structure,” said study leader Sabina Raducan. “This loose ‘debris’ is held together by gravity, among other things.”

Firmer inside

Still, previous simulations of the DART mission’s impact assumed a much sturdier interior of Dimorphos. And that may have been wrong. If it later turns out that Dimorphos also mainly consists of loose material, DART will hit him much harder than intended. “So this could drastically change the outcome of the collision,” emphasizes Raducan.

Effects

Rather than leaving a small crater on the 160-meter-wide asteroid, the impact of DART at 24,000 kilometers per hour could completely deform Dimorphos and even change it beyond recognition, the researchers say. This means that the asteroid is deflected much more strongly. In addition, much more material will be thrown off by the impact than predicted.

Nothing more to do

At the moment, however, there is nothing more that can be done. Didymos is expected to pass through Earth next fall. And researchers have devised it in such a way that DART will ram the moon Dimorphos at exactly that moment. Because this happens relatively close to Earth, scientists can study the fatal impact of DART and its immediate aftermath with telescopes from the ground and in space.

HERA

Subsequently, the CubeSat HERA will be launched in 2024, which will further investigate the aftermath of the bombing. The satellite will approach the moon’s surface as far as 200 meters. This allows Hera to produce high-resolution images – 2 cm per pixel. And then we will also find out how serious Dimorphos is after the collision.

“To get the most out of the HERA mission, we need to understand the potential impact of the collision,” said researcher Martin Jutzi. “Our work therefore adds an important potential scenario that forces us to broaden our expectations in this regard. This is not only relevant in the context of planetary defense, but also expands our understanding of asteroids in general.”