Osiris-Rex: Asteroid Bennu 'is a journey back to our origins

Nasa's Osiris-Rex capsule will come screaming into Earth's atmosphere on Sunday at more than 15 times the speed of a rifle bullet.

It will make a fireball in the sky as it does so, but a heat shield and parachutes will slow the descent and bring it into a gentle touchdown in Utah's West Desert.

The capsule carries a precious cargo - a handful of dust grabbed from asteroid Bennu, a mountain-sized space rock that promises to inform the most profound of questions: Where do we come from?

"When we get the 250g (9oz) of asteroid Bennu back on Earth, we'll be looking at material that existed before our planet, maybe even some grains that existed before our Solar System," says Prof Dante Lauretta, the principal investigator on the mission.