Tiny Asteroid to Make Earthly Close Encounter

The asteroid, which could be as small as a bus or as big as a house, will buzz Earth at a very safe distance of 23,900 miles today (Sept. 7).

A tiny asteroid is to make a very close approach with Earth today (Sept. 7), zooming harmlessly by at a distance of only 23,900 miles (38,500 kilometers) -- around 10 times closer to Earth than the moon.

The space rock was spotted by the Mt. Lemmon Survey's 60-inch telescope near Tucson, Ariz., on Sept. 5 and it quickly became clear that the asteroid, called 2016 RB1, was going to breeze by and not impact our atmosphere. It is set to make its closest approach at 1:28 p.m. ET.

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There is a little uncertainty in its size, with estimates putting it between 4-14 meters (13-46 ft) wide. As a comparison, the meteor that exploded over the Russian city of Chelyabinsk in 2013 was thought to be around 17 meters (56 ft) wide, causing over 1,000 injuries and structural damage when the shock wave made contact with the ground.

It is not known what material 2016 RB1 is made of, but if it was to hit Earth, it would most likely mostly burn up in the atmosphere with significantly less energy than the 2013 event. And as 70% of the planet is ocean, the impact would likely go unnoticed except, perhaps, by global infrasound stations and military satellites.

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As astronomical surveys become more sophisticated, astronomers are getting very good at seeing smaller chunks of space rock before they get close, an ability that was dramatically showcased in 2008 when the Catalina Sky Survey saw a dinky 3-meter (10 ft) asteroid, called 2008 TC3, on a collision course with our planet. The discoverers were able to identify the region and time of impact with great precision, making 2008 TC3 the first Earth-impactor to be identified 19 hours before it hit. Meteorite hunters even found fragments of the resulting meteor scattered over the Sudan's Nubian Desert.

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Most recently, astronomers discovered the asteroid 2016 QA2, measuring 25-55 meters (80-180 feet) wide, one day before it came within 50,000 miles from Earth.

Also, in 2011, astronomers spied the 2-3 meter-wide asteroid 2011 CQ1, realizing it would be the "closest near miss on record" of a near-Earth object (NEO), coming within 3,400 miles (5,480 kilometers). The same year a 5-20 meter-wide asteroid flew over the Southern Hemisphere at a close approach of 7,400 miles (12,000 kilometers), causing it to be greatly affected by Earth's gravity and catapulted over the Northern Hemisphere.

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However, probably the most famous "quasi-near miss" was The Great Daylight Fireball of 1972 when a 3 meter-wide meteoroid entered our upper atmosphere for a few seconds and left again after passing over the US. But as it hit the atmosphere, it didn't miss us at all -- it was technically an asteroid "catch-and-release!"

Our solar system is buzzing with thousands of NEOs, and many of the smallest objects have yet to be discovered, but we're getting better at seeing them approach from afar and the vast majority safely miss our atmosphere, as this latest discovery proves.

h/t Earthsky.org

GALLERY: Explore NASA's Asteroid Capture Mission:

On April 10, 2013, the White House and NASA released details of the US space agency's budget for the 2014 fiscal year. Included in the budget was a request for over $100 million to begin work on the Asteroid Retrieval and Utilization Mission. The mission would see a robotic spacecraft rendezvous with a small asteroid, which would then steer the space rock to the Earth-moon libration point (EML2) -- a region of gravitational stability beyond the far side of the moon. A manned mission would then meet the "tamed" asteroid to carry out science in-situ. It has been determined that such a mission would optimize the scientific gains while reducing risk and cost. On Wednesday, NASA released an animation detailing the stages of asteroid capture, here are the highlights.

Although its exact configuration has yet to be established, the robotic asteroid capture spacecraft will likely be solar powered and be propelled by an advanced ion drive. Optimistic estimates put a 2017 launch window on the first phase of the mission.

When approaching the asteroid, the spacecraft will jettison the hatch covering the folded asteroid "capture bag." According to the Keck Institute study that the mission is based on, the asteroid will be approximately 7 meters wide and have a mass of 550 tons.

During approach, the capture bag expands.

The capture bag will expand like an accordion's bellows in preparation for asteroid capture.

The spacecraft will likely carry out an automated docking maneuver with the asteroid. Seen here, a laser is emitted by the spacecraft, guiding it in.

When fully expanded, and centered, the capture bag will envelop the space rock.

A draw-string-like mechanism will allow the capture bag's opening to be closed around the asteroid, securely mating spacecraft with asteroid.

Once secured, the spacecraft will "de-spin" the asteroid and begin steering it toward the Earth-moon system. This will mark the first time in human history that we have ever changed the trajectory of a natural object in space.

Meanwhile, preparations will be underway for a manned expedition to the captured asteroid. Seen here, NASA's future Space Launch System (SLS) rocket blasts off.

NASA's Orion space capsule will take a team of astronauts to the asteroid's parking orbit at EML2.

The Orion capsule will perform a docking maneuver with the robotic asteroid capture spacecraft after several days transit.

With the asteroid secure, astronauts will have the freedom (and time) to carry out extensive studies during extravehicular activity (EVA).

With the science done and samples collected, the Orion capsule returns to Earth.

The entire mission will culminate in the spashdown of the Orion capsule with astronauts on board. The asteroid will remain parked at EML2 for further study by followup missions to the lunar farside. You can watch the whole video on the NASA website: