What we learned from NASA's asteroid deflection test

Asteroid Dimorphos is a small space rock that orbits a larger companion. It gained attention when NASA investigated ways to alter its trajectory in case it ever threatened Earth.

The Double Asteroid Redirection Test (DART) hammered Dimorphos on September 26, 2022, marking a critical attempt to see if an oncoming threat could be diverted. The success of this mission offered a glimpse into strategies that could be used to avert future dangers.

Scientists from Politecnico di Milano and the Georgia Institute of Technology have recently analyzed the outcome of the DART mission. Their findings are published in two papers – one led by Professor Fabio Ferrari and the other coordinated by Professor Masatoshi Hirabayashi.

NASA’s asteroid deflection test

The test was an example of kinetic deflection, a method that uses a high-speed crash to change an asteroid’s path. The experts examined how momentum transfer occurs when a spacecraft strikes a target.

The collision threw out clouds of ejecta, an event that left behind scattered debris in space. The researchers could see how this ejected material took shape, thanks to observations from the Hubble Space Telescope.

“We used Hubble Space Telescope’s images and numerical simulations to quantify a viable mechanism of the ejecta evolution and successfully estimated ejected particles’ mass, velocity, and size,” explained Professor Ferrari.

“We also found complex interactions of such particles with the asteroid system and solar radiation pressure, i.e., sunlight pushing ejecta particles.”

How asteroid shape affects deflection

Curved surfaces direct momentum in different directions. This can reduce the overall push effect of the collision, and leave part of an asteroid’s spin or speed unchanged.

Investigations revealed how the curvature of Dimorphos could have altered the spray of material that resulted from the collision. If the surface is not flat, the debris scatters in unexpected ways.

“If the impact is large, more ejecta fly out of the surface but are more affected by surface tilts. This process makes the ejecta deviate from the ideal direction, reducing the asteroid push,” explained Professor Hirabayashi.

Scientists aim to gauge how shape, structure, and spin all interact. Any miscalculation could lead to a deflection that falls short.

Strategies for near-Earth objects

The researchers explored the idea of using several lower-energy impactors, especially for near-Earth objects with uneven shapes. This approach can increase the odds of success if one shot misses the ideal spot.

Scientists emphasize that hypervelocity collisions might behave differently on an oddly shaped rock than on a smooth surface. This difference can lower the efficiency of a single, high-powered strike.

Each mission needs careful preparation, including reconnaissance to help identify the best angles and times for deflection.

Protecting Earth from asteroid strikes

Some experts see these methods being used for other cosmic bodies. They point out that accurate data on shape and composition help refine any defense design.

Asteroid collisions are part of space’s natural cycle and have been occurring since the universe formed. Ancient craters on Earth and the Moon are relics of much bigger strike events that might happen again.

Experts note that what seems like a big crash may not always yield the desired change. Relying on one massive impact can come with risks if the body has unpredictable contours.

“Sending multiple smaller impactors not only results in a higher asteroid push but also potentially saves operational cost and increases tactical flexibility for deflection,” said Professor Hirabayashi. Careful testing is essential before rolling out these solutions.

Lessons from Dimorphos

Experts see a strong case for more missions that study small bodies up close. Future spacecraft will likely gather details on topography and internal makeup before any deflection is attempted.

Lessons from Dimorphos will guide the planning of new solutions. These steps might determine how we react to unforeseen cosmic hazards in future.

Researchers continue building on the data from NASA’s test. Their aim is to ensure that Earth has a plan if a wandering rock ever sets its sights on us.

The studies are both published in the journal Nature Communications.

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