NASA‘s proved in 2022 that humans could redirect ‘city killer’ asteroids away from Earth – but with unintended consequences that could put our planet in danger.
A pair of Italian astronomers found that when the Double Asteroid Redirection Test (DART) craft rammed the 560-foot-wide asteroid Dimorphos off its course, the collision created a cloud of 37 new space boulders that is shooting toward Mars.
If one of these boulders hit the red planet, it could create a crater between 200 and 300 meters across – 656 to nearly 1,000 feet.
The astronomers warned that if NASA needs to knock a killer asteroid off its collision course with Earth in the future it will be crucial to consider where the debris from such a spectacular crash would go – lest it ends up colliding with Earth after all.
Double Asteroid Redirection Test (DART), a box-shaped space probe, crashed into its target on September 26, 2022. It was humanity’s first planetary defense test.
The dust tail of the Didymos-Dimorphos asteroid system, captured on October 31, 2022 – over a month after the impact. The dust tail was separate from the debris created by the spacecraft collision.
During the DART mission, NASA used an uncrewed spacecraft to slam into Dimorphos at 14,000 miles per hour to see if it was possible to push a space rock off its orbit.
In the following weeks, NASA scientists confirmed that it had worked: The so-called ‘kinetic impact’ had changed the asteroid’s orbit in space.
A kinetic impact means smashing one thing into another thing, and it’s one of the possible strategies NASA would use in the event of an asteroid threatening life on Earth.
Dimorphos is part of a two-asteroid system, orbiting a larger asteroid called Didymos.
After the DART collision, Dimorphos orbited Didymos in 11 hours and 23 minutes – 32 minutes less time than it took before the spacecraft had crashed into it.
With such an impact comes collateral damage, though.
Scientists discovered that the DART mission left in its wake 37 newly formed boulders shooting through space, on a totally different course.
On their current trajectory, these boulders may collide with Mars, concluded study co-authors Marco Fenucci of the European Space Agency (ESA), and Albino Carbognani, of the Observatory of Astrophysics and Space Science in Bologna, Italy.
The boulders measure between four and seven meters across – 13 to 23 feet.
Based on observations from the Hubble Space Telescope, the boulders escaped the gravity of the Dimorphos/Didymos pair – taking a separate path from the 6,000-mile-long tail of dust and rocks created by the impact.
And their orbit could interfere with that of the Hera mission, an ESA spacecraft scheduled to intersect Dimorphos in 2026 to get a closer look at the DART impact’s effects.
When the DART spacecraft collided with Dimorphos, it created a 6,000-mile-long tail of dust and rocks
Brace for impact: NASA’s first ever ‘planetary defense’ spacecraft – sent to deflect an asteroid 6.8 million miles from Earth – hit on September 26, 2022. The graphic above shows how the mission worked
‘All the observations taken so far prove that DART has been a successful test for asteroid deflection since it managed to change the orbital period of Dimorphos and it did not create any other boulder that could impact on Earth,’ the astronomers wrote.
‘On the other hand, the findings presented in this work suggest that future missions involving an interaction with the surface material of [a near-Earth asteroid] shall be carefully planned,’ they added.
In the longer term, these boulders may intersect the orbit of Mars.
The planet has a thin atmosphere, so it’s more likely that a small meteoroid would make it through and to the surface than it would be on Earth.
Upon impact with DART, Dimorphos ejected a cloud of dust and debris – as well as at least 37 boulders that now tumble through space
This may take thousands of years, though.
‘Numerical simulations show that all the boulders of the swarm will cross the orbit of Mars multiple times in the future [20,000 years], Fenucci and Carbognani wrote.
These simulations included a computer-generated swarm of the 37 new boulders, and the astronomers argued that they give a reasonably accurate prediction for the behavior of the real ones.
‘Therefore, due to the orbit crossings happening in the long-term evolution, it is possible that some of the boulders will impact Mars in the future,’ they concluded.
This could happen within 6,000 years – possibly interfering with a future human colony on Mars.
Overall, though, the DART mission has been considered a success, though.
For the first time in history, humans had intentionally changed the movement of a celestial object.
Dimorphos was not on a collision course with Earth, but as a two-asteroid system it provided a unique opportunity to track changes to a small asteroid’s orbit around a large one.
That test was proof that it is possible to knock asteroids off their course to keep them from wreaking destruction upon the Earth.
If a killer asteroid threatens humanity in the future, this means that people should be able to divert its path and avoid disaster – they just may want to plan for where the debris will go.
They published their findings on arXiv.org, the physics community’s pre-print paper server.
