NASA scientists are baffled as an asteroid on course to strike Earth in the future is accelerating faster through space, new research has revealed.

101955 Bennu is a carbonaceous asteroid in the Apollo group discovered by the LINEAR project on September 11, 1999. The space rock is a hazardous object listed on the Sentry Risk Table with the second-highest cumulative rating on the Palermo Technical Hazard Scale. It currently has a 1-in-2,700 chance of impacting Earth in the future, which could change following new observations.

Scientists working on NASA’s OSIRIS-REx mission used data gathered before the probe’s arrival to calculate Bennu’s rotation speed.
The asteroid was previously measured to rotate once every 4.3 hours. However, new research has calculated it to be increasing by about one second every century.

Mike Nolan, lead author of the Lunar and Planetary Laboratory paper said: "As it speeds up, things ought to change, and so we're going to be looking for those things and detecting this speed-up gives us some clues as to the kind of things we should be looking for.

That was when we came up with this idea that it had to be accelerating.

“We should be looking for evidence that something was different in the fairly recent past and it's conceivable things may be changing as we go.”
The new research is not based on measurements from that probe, instead, it looks at data collected by two ground-based telescopes between 1999 and 2005 and by the Hubble Space Telescope in 2012.
The numbers caught scientists' eyes because they did not line up with predictions astronomers had calculated with the ground-based data.
Dr Nolan added: “We couldn't make all three of them fit quite right.
“That was when we came up with this idea that it had to be accelerating.”

​The giant space rock, dubbed by NASA Asteroid 2019 CM4, will make a so-called “Earth Close Approach” next week. The asteroid will zip past the Earth on Monday, March 11, more than a month after it was discovered. NASA’s asteroid trackers have narrowed the flyby down to 6.12pm GMT (UTC). Asteroid CM4 was first spotted by NASA’s Jet Propulsion Laboratory (JPL) on February 8, this year.
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Subsequent orbital calculations have given NASA a pretty good idea of the asteroid’s trajectory and size.
The JPL estimates CM4 measures somewhere in the range of 223ft to 492ft (68m to 150m) in diameter.
Compared to a London double-decker bus, the asteroid could be up to 18-times longer.
Even at the lower end of the scale, the colossal asteroid is still 30-times longer than a Queen Size bed and nearly 17-times longer than a Volkswagen Beetle car.
With these terrifying dimensions in mind, the good news is NASA does not expect CM4 to crash into Earth any time soon.