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An Atlas V rocket launched with NASA’s OSIRIS-REx mission to asteroid Bennu from Cape Canaveral Air Force Station at 7:05 p.m. NASA video. Posted Sept. 8, 2016.

MELBOURNE, Fla. — A NASA probe blasted off Thursday evening from Cape Canaveral on a seven-year, 4.4 billion mile journey to grab a chunk of a primitive asteroid and return it to Earth.

A 19-story Atlas V rocket carrying the $800 million OSIRIS-REx mission lifted off at 7:05 p.m., thundering aloft just before sunset with 1.2 million pounds of thrust.

The United Launch Alliance rocket climbed into the day’s last light, turning a smoky exhaust plume bright white and casting a shadow against the sky as it arced eastward over the Atlantic Ocean.

Nearly an hour later, the rocket dropped off the 4,600-pound spacecraft the size of a small SUV in what the launch team called a “very good orbit,” some 3,400 miles above the planet.

That started a two-year sail toward a rendezvous with Bennu, a near-Earth asteroid measuring 1,600 feet across.

The dark, carbon-rich space rock is a remnant of the solar system’s formation more than 4.5 billion years ago.

Scientists consider it a time capsule that may have preserved traces of organic compounds and water ice like those thought to have helped seed life on Earth, and possibly elsewhere.

“We’re really going back to the dawn of our solar system,” said Dante Lauretta, the mission’s lead scientist from the University of Arizona. “Some areas of this early solar system had key organic materials and ices that accreted, and we think that was really critical for establishing the habitability of our planet.”

That investigation represents the “origins” part of the OSIRIS-REx mission name, an acronym for “Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer.”

The only way to analyze the ancient material is to get it into laboratories on the ground.

To pull that off, the spacecraft built by Lockheed Martin first will take up to two years to create high-resolution, 3-D maps of Bennu’s surface — revealing objects as small as a penny — and analyze what it’s made of.

The maps should highlight the most scientifically interesting site for attempting to collect a sample.

In the summer of 2020, the spacecraft will extend an 11-foot robotic arm and drop down to give Bennu a “high-five” or “kiss.”

Lasting just five-seconds, the contact will be just long enough for a burst of compressed gas to blow loose gravel and dust through a filter on the end of the arm, trapping it.

The mission’s goal is to collect at least two ounces of the material called regolith, but the mission could vacuum up more than four pounds.

If the first try fails to gather enough material, two more attempts are possible.

Even if only the minimum amount is collected, it will be the largest sample returned from space since the Apollo moon landings.

While orbiting Bennu, the mission will study a phenomenon called the “Yarkovsky effect” that could help protect the planet from a dangerous collision with an asteroid.

Asteroids absorb sunlight and emit that energy as heat that creates a slight thrust, influencing their trajectories over time.

Current calculations project that Bennu, which passes close by Earth every six years, has a very small chance – 1 in 2,700 – of hitting Earth late in the next century.

“If you want to know where it’s going to be in the future, and we do with this object, then you’ve got to have this part of the equation,” said Lauretta. “And we’re going to measure that precisely with this mission.”

Once collected, the asteroid sample will be stored in a capsule that will be dropped through Earth’s atmosphere in September 2023, targeting a touchdown in the Utah desert southwest of Salt Lake City.

NASA will carefully guard the sample to prevent potential contamination. Three-quarters of it will be saved for future scientists.

“Sample return really is the gift that keeps on giving,” said Lauretta. “Generations into the future are going to have access to this material. They’re going to be asking their own questions.”

Follow James Dean on Twitter: @flatoday_jdean