By Carol McGrath and Su-Ling Goh Global News
Published February 4, 2023
7 min read
NASA spent more than US$300 million on a spacecraft so they could smash it into pieces last year.
It sounds unbelievable, but it was done in the name of planetary defence.
The mission was part of a bigger effort to find a way to protect our planet from an asteroid that could end life on earth.
If that sounds extreme, then consider that meteors are bombarding our planet on a regular basis. According to NASA, it’s estimated that there are over 6,000 hits each year.
They start off as asteroids in the far reaches of our solar system but their trajectory sends them hurtling as meteors toward Earth, where if they survive entry into the atmosphere, they land as meteorites.
Most are small and not very destructive but one day we could get hit by a big one and if it’s more than a kilometre wide, it will have catastrophic consequences.
For years, NASA, with help from 28 countries, has been working on a planetary defence system with the goal of keeping us safe from the one that could end it all.
The most recent step forward in planetary defence is a program called DART, which stands for Double Asteroid Redirection Test. It was the first mission of its kind. The concept was to move an asteroid by slamming a spacecraft into it.
“We know that the dinosaurs went extinct by an asteroid or comet that hurt the Earth millions of years ago. But we want to be able to do something about that going forward in the future,” explains Nancy Chabot, a planetary scientist at the Johns Hopkins Applied Physics Lab near Baltimore, Md., and the coordination lead on the DART Investigation Team.
The target for DART was a double asteroid system, Chabot explains.
The two asteroids are about 11 million kilometres away from Earth. The larger asteroid, called Didymos is about 780 metres in diameter. It has a moon that goes around it called Dimorphos. It’s about 160 metres in diameter.
On Nov. 23, 2021, NASA launched the DART spacecraft from California aboard a SpaceX Falcon 9 rocket, sending it on its long journey to Dimorphos.
The spacecraft was guided to the asteroids by a system called SMART Nav, which stands for Small-body Manoeuvring Autonomous Real-Time Navigation.
Chabot tells Global News’ The New Reality that it was a massive challenge for the spacecraft to hit something so far away. The team needed to develop something that would enable the spacecraft to steer itself, because it would be too far away, and travelling too fast, for the scientists to remotely guide it from Earth. Thanks to the SMART Nav system, the craft found its way to Dimorphos using technology, and not simply a hope and a prayer.
“It had to be smart enough to tell the difference between these two asteroids within the last hour of the mission and then command itself autonomously to fire its thrusters to ensure it identified Dimorphos and hit Dimorphos head-on.”
The team chose an asteroid that was not a threat to earth.
The spacecraft, which has a body the size of a vending machine, guided itself on a collision course with the asteroid, which is about the size of a small football field.
The success of the mission was to be measured by whether the crash altered the path Dimorphos follows through space.
“The goal of Dart was definitely all about asteroid deflection, not asteroid destruction. The idea is that this small nudge would add up to a bigger change in its position with time,” Chabot says.
Armed with a camera, the spacecraft provided NASA mission control real-time images as it moved into place for impact.
And looking back, the scientists say it worked.
“It successfully collided with an asteroid on Sept. 26, 2022, becoming humanity’s first demonstration of asteroid deflection,” Chabot says. “It’s terribly exciting that we’ve taken this first step in what’s called planetary defence.”
In fact, it turns out that the DART spacecraft did a better job than anticipated. Through observations from various telescopes around the world, the DART team was able to compare the orbit that Dimorphos followed before and after the impact. Scientists have discovered that Dimorphos’s orbit changed significantly after being struck.
Of course, all of the important work being done by NASA wouldn’t have been possible without the knowledge we gain from the study of meteorites that land on Earth.
“These different materials are going to react differently. If you use a kinetic impactor like DART, where you crash a spacecraft into it, you can see where that’s going to react differently depending on the composition of that material,” Chabot says.
One of the thousands of meteorites landing here on earth crashed through a roof in Golden, B.C., in October 2021.
Ruth Hamilton was asleep in her bed when she heard a loud crash. “I was so scared. I don’t think I’ve ever been as scared as anything else in my whole life. I jumped out of bed, turned on the light, and all I could see was a hole in my ceiling.”
On her bed, just centimetres away from where she had been sleeping was a rock. It could have been fatal had it landed on her.
At first, she didn’t realize what she was dealing with. “I didn’t know how special it was because it was just the rock at that time. And then later on, we figured out that it was a meteorite.”
The meteorite has now been officially given the name: the Golden Meteorite.
There’s been a lot of interest in the meteorite from around the world. So far, Hamilton has provided a slice of the space rock to the team at Western University in London, Ont., for research.
Hamilton is still trying to figure out what she wants to do with the rest of it. “I haven’t quite decided what to do with it. There are lots of organizations out there that want it.”
Chris Herd is one of the people who would love to examine the Golden meteorite.
He is a professor at the University of Alberta’s department of Earth and atmospheric sciences in Edmonton. He’s also the curator of Canada’s largest university-based meteorite collection.
More than 350 space rocks are housed in the meteorite museum at the U of A.
Global News’ The New Reality got to get a close-up look at the collection, as well as the cameras Herd uses to track shooting stars.
Herd says he can figure out where in the universe the meteorites come from based on their trajectory in the sky.
That’s important knowledge if we are going to figure out where the next potentially deadly asteroid might come from.
Herd was able to capture images of the meteor while it was on its journey to Hamilton’s house.
He says Western Canada is a particularly good place for seeing meteors and finding meteorites.
“We are in the Prairies, it’s relatively flat,” and that means good sightlines. There’s also the nature of the surroundings, he explains. “Because the land use in this part of the world is mostly farming and ranching, if something does fall, then the chances are better of actually getting out and finding it on the surface and being able to collect it.”
Herd says he is working on ways to better preserve the meteorites he manages to acquire, including “things like keeping them cold and keeping them out of the Earth’s atmosphere.”
Recently, he was sent part of a 15.2-tonne meteorite that fell in Somalia. And he says that what he discovered was quite surprising.
“I discovered that there were some unusual-looking minerals inside, really — minerals that I couldn’t identify,” Herd says. “And so, when we delved into it more deeply, we realized that we had found three new minerals, minerals that have never been found before in this particular meteorite.”
Such knowledge about what makes up the meteorites and where they come from is important for future asteroid-moving missions.
Herd says the more we know about potentially hazardous asteroids, both in terms of their physical properties and their composition, as well as where they come from, the more prepared we will be.
“That really does buy us time and understanding for when there might be something even larger that is potentially hazardous.”
After all, the DART mission is just the beginning of what NASA hopes can be accomplished in the future if we find our Earth in peril.
According to Chabot, we still have plenty of time to figure it out. “You can actually have a warning time of 100 years. So you’re in the situation where you could do something like DART, where you could just give it a small nudge many years in advance and avoid a collision with the planet.”