Material from an asteroid will "come screaming into Earth's atmosphere on Sunday at more than 15 times the speed of a rifle bullet" – but it has all been planned by space scientists, who hope it will answer some of their biggest questions.
Nasa's spacecraft Osiris-Rex will send a small capsule back to Earth carrying a "precious cargo", said BBC News: a "handful" of dust and rock weighing just 250g from a nearby asteroid, Bennu.
The capsule will enter the Earth's atmosphere before drifting to the ground in the Utah desert by parachute. The sample "promises to inform the most profound of questions: where do we come from?", said the broadcaster.
It will contain "material that existed before our planet, maybe even some grains that existed before our Solar System", said Dante Lauretta, the principal investigator on the mission. "We're trying to piece together our beginnings. How did the Earth form and why is it a habitable world? What is the source of the organic molecules that make up all life on Earth?"
Researchers are interested in the 500-metre-wide Bennu because it appears to be "rich in carbon", an element that underpins all life on Earth, and contains traces of water, "another vital ingredient".
Scientists are also interested "for a more immediately relevant reason": self-preservation. Bennu is regarded by Nasa as one of the most dangerous items in the solar system, with about a 1 in 1,750 chance of it colliding with Earth by 2300. Characterising asteroids would help "work out how a looming impact might be averted".
By the time scientists have analysed the material from Bennu, "it is unlikely that any aspect of its formation, evolution and orbital history, composition and components will be unknown", wrote Monica Grady for The Conversation. This will allow an effective “Earth rescue” mission to be launched.