The threat of an asteroid colliding with Earth is a common source of anxiety – both for astronomers and the public. Impact events have the potential to cause worldwide casualties and disruption, and it is only a matter of time before one comes our way.
What would we do when that happens? We have previously spoken about how the UK plans to protect space, but what is humanity doing to protect our planet from extraterrestrial threats?
Until very recently, scientific consensus held that the most effective way to protect Earth from an asteroid would be to destroy it in space. Suggestions have included setting off a nuclear explosive (as they tried in Armageddon) or using an ion beam or focused solar energy to deflect the asteroid. However, NASA research found that destroying an asteroid in space would be much more complicated than initially thought.
As such, research has instead shifted towards the concept of kinetic deflection. It involves hitting an asteroid with a fast-moving object to alter its trajectory, thereby missing Earth completely. While the calculations involved are complex, the concept itself is straightforward.
And this is exactly what NASA plans to test with its DART Program, launched on the 24th of November.
The Double Asteroid Redirection Test (DART) is a spacecraft designed to collide with an asteroid to measure how effectively we can redirect its orbit. NASA chose Dimorphos, a moonlet orbiting a larger asteroid, as its target. Dimorphos is an ideal candidate because NASA can change its orbit around Didymos by a minuscule amount with no threat to Earth.
The experiment will occur roughly 6.7 million miles away from us in September 2022. DART will collide with Dimorphos at a speed of 6.6km/s to knock it into a new orbit around Didymos. Despite the DART satellite being 19 metres long, it will collide with enough force to alter the 163-metre long asteroid’s course by roughly one per cent.
Around ten days before impact, the DART spacecraft will release a microsatellite to monitor the collision. NASA chose the Italian aerospace company, Argotec, and its microsat, LICIACube, which is invaluable recognition for the company and its work. LICIACube will fly within 55 kilometres of the collision and send image data back to Earth. Ground satellites will then continue to monitor the asteroids for months after the experiment.
While this is a small-scale experiment, its results could be ground-breaking for the future of humanity. Astronomers believe the threat of large-scale asteroid collisions is low, at least during our lifetimes, but the law of probability states it will happen in the future.
As such, we must be prepared with solutions. The DART mission is the first time we have created a practical experiment to deal with satellites, so it will set a precedent for future research. If it works, the findings can theoretically be scaled up to suit different asteroids.
However, we will not have conclusive evidence of the experiment for some time. It will take ground satellites weeks or months to monitor the change. Luckily, we can play the waiting game, and it will be fascinating to see what happens.