At 9.17am on Tuesday (AEST), a $330 million (US) probe will smash to pieces when it crashes into an asteroid. And NASA is doing it all on purpose - in the name of protecting the planet.
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At the end of the Obama presidency, the Office of Science and Technology Policy led a report about what the US needs to do to better prepare for a potential asteroid impact.
The report lists a lot of work including better monitoring to find asteroids to testing potential options for redirecting a potentially hazardous asteroid.
In 2017, NASA got approval to proceed with DART - the Double Asteroid Redirection Test. It was launched last November and has been on a 10-month journey.
The target asteroid is 65903 Didymos. It is a binary asteroid, meaning there are two asteroids orbiting around each other. The larger asteroid, Didymos, is about 780 metres wide while Dimorphos is 160m wide.
The two asteroids are separated by about 1km, with Dimorphos orbiting like a tiny moon.
The combined asteroids weigh about 530 billion kilograms, not a small thing to move.
It poses no danger at all and is not a worry. Think of it like an emergency evacuation drill or fire drill.
We practice those at our workplaces and schools so we know what to do, and how to do it, in the event we need to. DART is doing this on behalf of Earth.
As DART has approached the asteroid, scientists have done a few adjustments to line up the spacecraft as best as possible. Now, it is on autopilot, headed to the target spot on the asteroid.
At about an hour before impact, it will only finally be able to see the two asteroids as separate targets. As it gets closer, we'll see the asteroid closer and closer until a few seconds before, we can start to see details on the asteroid until it crashes - at a speed of nearly 24,000km/h.
After it hits, hopefully, the impact will have changed its orbit around the larger object. This is one of the reasons why this system was chosen - we can measure the change by how its orbit around the bigger asteroid changes. It also means the gravity of the larger asteroid will keep the smaller one from flinging out in space.
Telescopes on Earth will then measure how much of a change DART inflicted by constantly monitoring the two asteroids.
On board DART, an Italian-built satellite called LICIACube, hitched a ride.
A few weeks ago, it hopped off and has been trailing DART. It will fly past, imaging the impact site as well as flying through the debris and rock that comes off, to get exact measurements of the composition of the asteroid.
Sixty-six-million years ago, a 15-20km asteroid hit the Earth, and wiped out lots of life - including the dinosaurs.
On Tuesday, Earth learns to fight back with DART.
- Brad Tucker is an astrophysicist and cosmologist at Mt Stromlo Observatory and the National Centre for the Public Awareness of Science at the ANU.
