Why is NASA crashing a spacecraft into an asteroid? Photo: AFP / NASA / Johns Hopkins APL / Steve Gribben
In eight days NASA will deliberately crash a spacecraft into an asteroid in a US$330 million (NZ$550 million) attempt to change the asteroid's course.
It's the world's first full-scale mission to test technology for defending Earth against potential asteroid collisions.
So what is the DART mission? And should we be concerned about NASA's strike?
Why is NASA doing this?
Space engineers want to learn how to deflect asteroids in the event one is ever discovered on a collision course with Earth.
The DART mission, or the Double Asteroid Redirection Test, will help determine if intentionally crashing a spacecraft into an asteroid is an effective way to change its course.
Cue references to disaster films like Don't Look Up and Armageddon, although astronomers believe it's unlikely such devastation could happen in the near future.
DART is the world's first full-scale mission to test technology for defending Earth against potential asteroid collisions.
By studying the asteroid's path after the collision, scientists believe they will better understand how collisions could be used to deflect Earth-bound asteroids and comets.
DART's target, Dimorphos, is 160 metres in diameter and orbits its parent Didymos. Photo: JIM WATSON
What is the name of the asteroid that NASA is going to hit?
The mission is targeting Dimorphos, a small "moonlet" or asteroid orbiting a larger near-Earth asteroid named Didymos.
Near-Earth objects are asteroids and comets with orbits that place them within 50 million kilometres from Earth. NASA says detecting the threat of NEOs that could cause grave harm is a primary focus.
Dimorphos is about 160 metres in diameter and is the smallest thing NASA has ever tried to hit.
The larger asteroid Didymos is about 780 metres in diameter. It's name is the Greek word for "twin", a nod to how the asteroid forms a binary system with the smaller asteroid.
DART will be travelling at roughly 6 kilometres per second when hits Dimorphos.
When will Dart crash into the asteroid?
Monday, 26 September at about 7.14pm US time, is the expected time (that's about 11:14am Tuesday, 27 September NZT).
It's been a 10-month journey for the spacecraft that, not measuring its two solar panel wings, is the size of a small car.
Does the asteroid pose any threat?
Nope, the asteroid poses no threat to Earth.
"This is humanity's first ever planetary defence test," Bobby Braun, head of space exploration at the Johns Hopkins Applied Physics Lab said at a media briefing.
"Everything about this is a test. It's being done in a safe manner. There's 0 per cent chance that this asteroid could come towards the Earth, so it's actually an ideal set-up for our science team, for the engineering team … and for those of us around the world to learn and to make ourselves better through this mission."
On the day of impact, images will stream back to Earth via images recorded by LICIACube, a small satellite provided by the Italian Space Agency.
The briefcase-size satellite is now travelling behind the spacecraft to record the collision.
At the time of impact, Didymos and Dimorphos will be located within 11 million kilometres to Earth.
What will happen after impact?
The plan is to fly the DART spacecraft directly into the moonlet bumping it hard enough to shift its orbital track around the larger asteroid.
After impact, scientists will use ground-based telescopes to observe if Dimophos's orbit has changed, and by how much.
As for fears of comets and a catastrophic impact with Earth, NASA says there are no known threats to our planet for at least the next 100 years.
The data collected will contribute to planetary defence strategies, especially the understanding of what kind of force can shift the orbit of a near-Earth object that could collide with our planet if one is ever discovered.
- ABC