Bennu asteroid keeps spinning faster and scientists aren't sure why

A distant space rock called Bennu is spinning faster meaning its rotation period is getting shorter by about one second every 100 years - but scientists are still trying to figure out why. NASA is observing the asteroid to help them understand the evolution of other similar objects, their potential threat to Earth, and if they could be mined for resources. Scientists used data gathered during the OSIRIS-REx mission, before the probe's arrival, to calculate that Bennu's rotation rate is speeding up over time. Bennu is 70 million miles (110m km) away from Earth. As it moves through space at about 63,000 miles per hour (101,000 km per hour), it also spins, completing a full rotation every 4.3 hours.