NASA is planning to launch a probe to study an asteroid that could one day pulverize the Earth.
The asteroid, named Bennu, crosses Earth’s orbit once every six years and has gotten ever closer since it was discovered in 1999, astronomers told the Sunday Times of London (paywall).
In 2135, Bennu will fly between the moon and Earth — a hair’s breadth in space terms, the Times reported. That’s so close that gravity from the Earth could effect Bennu’s orbit, “potentially putting it on course for the Earth later that century,” said Dante Lauretta, a professor of planetary science at Arizona University.
Bennu is about 1,600 feet in diameter and travels around the sun at an average of 63,000 mph.
The chance of an impact is small but significant, and if it happens, would be equivalent to triggering 3 billion tons of high explosive, 200 times the strength of the atomic bomb dropped on Hiroshima.
“Bennu falls on the boundary, in terms of size, for an object capable of causing a global catastrophe,” Professor Mark Bailey of Northern Ireland’s Armagh Observatory told the Times.
The scenario eerily replicates the danger depicted in the 1998 movie “Armageddon,” in which Willis’ character was sent to implant a nuclear weapon to destroy an asteroid aiming for the Earth.
NASA will launch the Osiris-Rex probe mission to Bennu in September.
The probe’s journey will involve a year of orbiting the sun to build up speed before it slingshots back around Earth, using the planet’s gravity to align its orbit with the asteroid’s, the Times reports. They will rendezvous in August 2018.
Osiris-Rex will then spend a year mapping the asteroid and then hover above its surface to pick up some rubble, before flying back to Earth.
For scientists, the chance of obtaining chunks of a carbonaceous asteroid is exciting. “Bennu is a carbonaceous asteroid, an ancient relic from the early solar system that is filled with organic molecules,” Lauretta explained to the Times. “Asteroids like Bennu may have seeded the early Earth with this material, contributing to the primordial soup from which life emerged.”
For the rest of the world, Osiris-Rex’s most important task may be the measurements it makes of a newly discovered force called the Yarkovsky effect, that can send asteroids careening around the solar system and potentially toward Earth.
This force makes Bennu’s trajectory hard to predict, but scientists know its position has shifted 100 miles since 1999.
“We need to know everything about Bennu — its size, mass and composition,” said Lauretta. “This could be vital data for future generations.”