Canadian tech helping to grab asteroid chunk
The OSIRIS-REx will attempt to get samples of 4.5-billion-year-old asteroid
At 7:05 p.m. Thursday, a team of scientists in Cape Canaveral, Fla., will watch as a rocket lifts a 6.2-metrelong spacecraft into the sky. OSIRISREx will spend two years travelling through space to the asteroid Bennu. The mission, with the help of Canadian science and engineering, will send a precious piece of the asteroid hurtling back to Earth and help scientists answer questions about our solar system’s deep history. Anear-Earth threat Out of all the asteroids in all the orbits in our solar system — there are millions — scientists chose Bennu. Why? Bennu comes extremely close to the Earth, almost as close as the moon, and orbits the sun in roughly the same plane as our planet, so it is more accessible than most. With a diameter of about 500 metres, Bennu also spins more slowly than a smaller asteroid typically would, making a tricky sampling manoeuvre feasible (more on that later).
There are eye-widening reasons, too: Bennu has a one in 2,700 chance of impacting our planet sometime between 2175 and 2199, classifying it as a “Potentially Hazardous Asteroid.” One of the spacecraft’s objectives is to measure the tiny push that happens when an asteroid absorbs and emits sunlight, known as the Yarkovsky effect. Understanding this effect will help astronomers predict Bennu’s path in the future.
Lastly, scientists believe Bennu is a rare B-type asteroid: a carbon-rich, primitive remnant of the early solar system — a cosmic “time capsule” — that may provide clues about the origins of life on Earth. Canadian lasers When it reaches Bennu in 2018, OSIRIS-REx will use a suite of five instruments to explore the asteroid. One of them, the OSIRIS-REx Laser Altimeter (OLA), was designed and built in Canada.
“You obviously have to bring some expertise to the table, and we have that expertise here in Canada,” said Michael Daly, OLA’s instrument scientist and York Research Chair in Planetary Science.
The instrument, built by a Canadian company, uses two lasers, a highenergy beam for distances of up to 7.5 kilometres and a low-energy one for distances of under 1.5 kilometres. By timing the gap between when a laser pulse is emitted and when it returns, OLA will allow the spacecraft to precisely calculate the distance between it and the asteroid.
That capability will help OSIRIS- REx navigate around Bennu. But OLA also has important scientific functions: by pinging lasers at the surface up to 10,000 times a second, the instrument will help create a high-resolution topographic map of Bennu. “Fundamentally with these asteroids, the shape is so, so important,” says Daly, to helping scientists understand the objects’ geology and evolution. Acareful dance Part of OLA’s job, along with the cameras and spectrometers on board, is to help identify and map the most scientifically interesting places to grab material from the asteroid’s surface. Once the team back on Earth selects a site, the spacecraft will use a novel “touch and go” technique to collect its sample.
OSIRIS-REx will never land on the asteroid. It will hover in close and extend a robotic arm, making contact for just five seconds. When the sampler head touches the surface, it will send out a jet of nitrogen gas to blow surface material into an internal chamber. The spacecraft has enough gas for three attempts. The science team wants at least 60 grams of material and as much as two kilograms.
After the sample is collected, OSIRIS-REx will begin a two-and-ahalf year trip back to Earth, eventually releasing its sample return capsule, which will come hurtling towards the Utah desert in 2023. Cosmic time capsule Because of the Canadian Space Agency’s participation, Canadian scientists are entitled to 4 per cent of the material collected from Bennu.
“This is the first time that Canada has ever participated in an asteroid return sample, so we’re super excited about having materials we can study directly,” says Kim Tait, curator of mineralogy at the Royal Ontario Museum and a collaborator on the mission’s Canadian science team.
Part of Tait’s job is to train graduate students to study the sample and get even younger students excited about it: because of the seven-year duration of the mission, “There are people who are still in school who will be studying this one day.”
Meteorites, pieces of asteroids that have broken up in our atmosphere and rained down on Earth, are nuggets of space history.
But meteorites are altered by their traumatic entry and contaminated by sitting on our planet, so a pristine asteroid sample from a known source is of irreplaceable scientific value.
“We wouldn’t be doing this if we knew what we were going to get,” Tait says.
Asteroids like Bennu and planets like Earth all formed as our solar system coalesced 4.5 billion year ago. But Earth has been scoured by dynamic geologic processes such as plate tectonics. On Bennu, “there’s no rain, there’s no wind. It’s just stuck,” Tait explains. For that reason, Bennu is like a “time capsule” that can tell scientists about the deep history of our solar system. The research team wants to know whether asteroids were the source of organic molecules that led to life on Earth, a finding suggested but not confirmed by meteorites. An uncontaminated sample from carbon-rich Bennu may help answer that question.
“That’s always the big question: where do we come from?” says Tait. “If we can get back to material that is from the beginning, and from the early solar system . . . Are there the things we need to seed life?”