Choosing the proper spot to smash a spacecraft into the floor of a hazardous asteroid to deflect it should be completed with nice care, in response to new analysis offered on the EPSC-DPS2025 Joint Assembly this week in Helsinki. Slamming into its floor indiscriminately runs the danger of knocking the asteroid by way of a ‘gravitational keyhole’ that sends it again round to hit Earth at a later date.
“Even when we deliberately push an asteroid away from Earth with an area mission, we should make sure that it does not drift into considered one of these keyholes afterwards. In any other case, we would be dealing with the identical affect risk once more down the road,” stated Rahil Makadia, a NASA Area Expertise Graduate Analysis Alternative Fellow on the College of Illinois at Urbana-Champaign, who’s presenting the findings on the EPSC-DPS2025 assembly.
NASA’s DART, the Double Asteroid Redirection Take a look at mission, struck the small asteroid Dimorphos, which is in orbit across the bigger asteroid Didymos, in September 2022. DART was a ‘kinetic impactor’ – successfully a projectile that slammed into the asteroid with sufficient power to nudge it into a brand new orbit, thereby proving that it’s attainable to deflect an asteroid that may very well be on a collision course with Earth.
A European Area Company mission referred to as Hera will follow-up on the DART affect when it reaches Didymos and Dimorphos in December 2026.
The place DART struck on Dimorphos was of comparatively little concern, for the reason that Didymos system is simply too large to be deflected onto a collision course with Earth. Nonetheless, for an additional hazardous asteroid orbiting the Solar, even a small variation in its orbit may ship it by way of a gravitational keyhole.
The keyhole impact revolves round a small area of house the place a planet’s gravity can modify a passing asteroid’s orbit such that it returns on a collision course with that planet at a later date. On this manner, a gravitational keyhole unlocks extra harmful orbits.
Ought to a kinetic impactor mission much like DART nudge a hazardous asteroid in order that it passes by way of a gravitational keyhole, then it solely postpones the hazard.
“If an asteroid handed by way of considered one of these keyholes, its movement by way of the Photo voltaic System would steer it onto a path that causes it to hit Earth sooner or later,” stated Makadia.
The trick, due to this fact, is to seek out the perfect spot on the floor of an asteroid to affect with a spacecraft in order that the probabilities of pushing it by way of the keyhole are minimized.
Every level on the floor of an asteroid has a unique likelihood of sending the asteroid by way of a gravitational keyhole after deflection by a kinetic impactor. Makadia’s staff has due to this fact developed a method for computing likelihood maps of an asteroid’s floor. Their methodology makes use of the outcomes from DART as a information, though every asteroid, with its personal traits, can be subtly totally different.
The asteroid’s form, floor topology (hills, craters and so on), rotation and mass all should be decided first. Ideally this is able to be completed with an area mission to rendezvous with the asteroid, producing high-resolution photos and information. Nonetheless, this may not be attainable for all threatening asteroids, notably if the time between discovery and affect on Earth is brief.
“Thankfully, this whole evaluation, at the least at a preliminary stage, is feasible utilizing ground-based observations alone, though a rendezvous mission is most well-liked,” stated Makadia.
By computing the next trajectory of the asteroid following a kinetic affect, and seeing which trajectories could be probably the most harmful, scientists can calculate the place the most secure location to strike on the asteroid’s floor can be.
“With these likelihood maps, we will push asteroids away whereas stopping them from returning on an affect trajectory, defending the Earth in the long term,” stated Makadia.
