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Tony Clement, president of the Treasury Board, announces Canada's contribution to an international space exploration mission to return a sample from an asteroid during a press conference at the Royal Ontario Museum in Toronto on July 17, 2014.DARREN CALABRESE/The Globe and Mail

It's scarcely bigger than a city block – just 493 metres across – yet understanding the nearby asteroid Bennu could well be a matter of life and death.

That's the word from Canadian researchers who are participating in a NASA-led robotic mission to Bennu called OSIRIS-REx that is set to launch in 2016.

The involvement is ongoing, but on Thursday the Canadian Space Agency announced a $7-million contract for MDA Corporation to build an altimeter that will fly on the spacecraft and measure its rocky surface in detail. The heart of the device includes a lidar system built by the Toronto-based company Optech.

"This is a great opportunity to use one of our key technologies," said Stéphane Dejardins, the agency's director of space exploration projects.

The system is a spinoff of one used to make atmospheric measurements of Mars, part of the Phoenix mission which landed on the red planet's north polar plain in 2008.

But instead of looking up into thin Martian air, the new device will be directed at Bennu's previously unexplored surface to map its topography and help researchers locate an interesting spot where the spacecraft can swoop down and grab a sample for return to Earth.

"It's a bit of a slow dance getting to understand the environment and getting in closer and closer," said Michael Daly, a space scientist at York University and one of the Canadian leaders of the mission.

Bennu is an object of high interest in part because it belongs to a class of asteroids that are carbon-rich and are thought to contain organic molecules. This is the kind of material that may have been deposited on Earth during the solar system's formation, helping to jumpstart the origin of life.

In exchange for Canada's participation in the mission, worth $61-million in total, a 4 per cent shared of the material OSIRIS-REx gathers at Bennu will end up in Canadian labs once the sample is returned in 2023.

But there is also a dark side to Bennu: calculations suggest it has a 1 in 2700 chance of striking Earth late in the next century. While the probability of impact is low, it's one of many such small objects thought to threaten Earth at some point in the future. Scientists have argued that more information Earth-crossing asteroids is need to come up with effective strategies for planetary defence.

To that end, the Canadian component of the mission will provide the first direct measurement of the Yarkovsky effect, a slight but persistent force on an asteroid due to its absorption of sunlight.

"It's one of the things that makes asteroid orbits difficult to predict in the long term, which is an Earth safety issue," Dr. Daly said.

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