MIAMI: The US space agency counted down Thursday to the launch of its first ever mission to collect dust from an asteroid that may have delivered life-giving materials to Earth billions of years ago.

The unmanned spacecraft, known as OSIRIS-REx, is poised to blast off at 23:05 GMT atop an Atlas V rocket in Cape Canaveral, Florida. The weather forecast is 80 percent favorable for liftoff.

The $800 million mission will travel for two years on a journey to Bennu, a near-Earth asteroid about the size of a small mountain.

The solar-powered spacecraft's main goal is to gather dirt and debris from the surface of the asteroid and return it to Earth by 2023 for further study.

Learning more about the origins of life and the beginning of the solar system are key objectives for the SUV-sized OSIRIS-REx, which stands for Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer.

But the mission should also shed light on how to find precious resources such as water and metals in asteroids, a field that has generated increasing interest worldwide.

“We are going to map this brand new world that we have never seen before,” said Dante Lauretta, OSIRIS-REx principal investigator with the University of Arizona, Tucson.

Using a suite of cameras, lasers and spectrometers, “we are really going to understand the distribution of materials across the surface of that asteroid,” he added.

“We are a trailblazer for that kind of activity because our science requires it.” The spacecraft is expected to reach Bennu in August 2018 and spend two years studying it before it begins the sample collection attempt in July 2020.

'Gentle high five'

NASA hopes OSIRIS-REx will bring back the largest payload of space samples since the Apollo era of the 1960s and 1970s, when American explorers collected and carried back to Earth some 360 kilograms of moon rocks.

The collection device, known as the Touch-and-Go Sample Acquisition Mechanism (TAGSAM), should pick up about two ounces from the asteroid, but in tests so far it has generally picked up five times that amount.

TAGSAM contains a type of reverse-vacuum mechanism that was invented by a Lockheed Martin engineer who tested the concept a decade ago using a red plastic Solo cup in his driveway.

The spacecraft will not land on the asteroid, but will get very close and reach out with an arm like a pogo-stick for a quick, three-to-five second maneuver.

Rich Kuhns, OSIRIS-REx program manager with Lockheed Martin Space Systems in Denver,described the movement as a “gentle high-five.” The sample collector will shoot a bit of compressed air at the asteroid and gather the dust it kicks up in a container.

“Three-quarters of the sample will be set aside for future researchers -- for the science questions we haven't figured out to even ask yet,” said Gordon Johnston, an OSIRIS-REx program executive at NASA headquarters.

NASA has also promised four percent of the sample to its major partner in the effort, Canada, and another half-percent to Japan.

Yet another aim of the mission is to measure how sunlight can nudge asteroids as they orbit, a phenomenon known as the Yarkovsky effect, so scientists can better predict the long-term risk of asteroids like Bennu colliding with Earth.

Past missions

OSIRIS-REx may be the first of its kind for the US space agency, but it was the Japanese space agency JAXA that first proved sample collection from an asteroid was possible.

JAXA's Hayabusa spacecraft crash-landed into the surface of its target asteroid but nevertheless managed to return a few micrograms of material in 2010.

JAXA launched a follow-on mission, Hayabusa 2, in December 2014. It should reach the asteroid Ryugu in 2018.

The Hayabusa 2 spacecraft will place on the space rock's surface a small lander named Mascot, produced by the French and German space agencies, and return asteroid samples by 2020.