The Dart mission slammed into egg-shaped Dimorphos to demonstrate how hazardous rocks posing a threat to the Earth could be moved out of the way.
It was very successful, but even more so because the impact dug up a million kilograms of surface material.
When this shot out into space it boosted the momentum exchange.
Scientists working on the project have even been able to put a value on the effectiveness, a quantity they call “beta”. It’s 3.6.
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- The Hubble Space Telescope saw a trail of debris from the asteroid after impact
“If you blast material off the target then you have a recoil force,” explained mission scientist Dr Andy Cheng from the Johns Hopkins University Applied Physics Lab (JHU-APL).
“The result of that recoil force is that you put more momentum into the target, and you end up with a bigger deflection.
The Double Asteroid Redirection Test (Dart) was a controlled experiment that took place some 11 million km (7 million miles) from Earth.
It saw the refrigerator-sized Nasa satellite drive straight into 160m-wide (525ft) Dimorphous at 22,000km/h (14,000mph), destroying itself in the process.
The space rock orbits a much larger (780m wide; 2,550ft) object called Didymos. Before impact, the time taken for Dimorphos to make one circuit of its sibling was 11 hours and 55 minutes.
The subsequent telescope observations indicated this orbital period was reduced to 11 hours and 23 minutes – a change of 32 minutes.
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