Image copyright Getty Images Image caption NASA is dropping a probe on the asteroid Bennu to test a new plan to deflect a threatening near-Earth object
Next month Nasa will begin testing a concept to deflect a potentially threatening asteroid by dropping a spacecraft on it.
The Deep Impact (DT) mission involves the release of a 200m-long (660ft) probe that will fly past the object known as Bennu, in the southern hemisphere, on the night of 25 April.
NASA wants to check if there is a safe path for a future probe to visit the asteroid.
Only smaller NASA probes, launched to explore the Moon, can fly towards asteroids.
From 1992 until 1995 a small craft known as Stardust orbited comet Wild 2, only about 25 miles (40km) away. By carefully observing the comet’s orbit, it revealed material left over from the creation of the solar system 4.5 billion years ago.
The CBOS (Contingent School of Earth Systems Analysis) launched in 2001 is an important early stage in discovering asteroids.
Using it is a chance to improve asteroid detection technology because it works in the opposite direction of Earth’s motion. This gives the spacecraft a period of about 18 months to explore the flyby target, and then it is expected to fall back to Earth.
NASA’s science mission director, Dan Werthimer, said he had high hopes.
“When you look at the science we’re looking at, this is like looking up at a bridge and hoping that you have enough time to get to it and save yourself,” he said.
“This is a good opportunity to put out the American flag on a space rock and send a good confidence statement to our planetary defence team.”
How does NASA propose to crash the space probe into the moon-like object?
Image copyright Getty Images Image caption NASA mission system specialist Charles Elachi (bottom left) spoke to the media at its headquarters in Maryland
Nasa wants to use an atmospheric drag technique – where a spacecraft enters a body and the air gets heavier and heavier until it falls into a body that is just 50m away from the target body.
This mission would test a technique that would allow an unmanned spacecraft to fly into an object, drop off the probe, and then come back in half a decade or so for a long-term mission.
It also has the potential to make space exploration more affordable.
What is NASA’s new plan for deflecting an asteroid?
Image copyright NASA Image caption The D80 captured some of the mystery debris when it came to Bennu in 2008. NASA will test another technique to deflate an asteroid during Deep Impact in April
So-called “deflection” is the overriding goal.
It involves using a method which uses a probe launched from Earth rather than smashing one into a space rock.
The probe would be fired from the ground by a rocket. This would propel the probe over the asteroid, and then after a few days, it would fall back to Earth.
When it falls down into the atmosphere, it is expected to become too heavy to fly for much longer.
This would create a catastrophic enough turn in its trajectory that a spacecraft travelling behind it would be launched into an orbit around the asteroid that would land it on a path around Earth.
Rather than a spacecraft bombarding a space rock, instead it would deflect a rock that is already moving in our direction, with the ability to survive after it crashes into our planet.