Their target is an asteroid named Bennu, a 85.5-million-ton (77.5 million metric ton) space rock that is on track to swoop within 4.6 million miles (7.5 million kilometers) of Earth's orbit between 2175 and 2199. Although Bennu's chances of striking Earth are slim — at just 1 in 2,700 — the asteroid is as wide as the Empire State Building is tall, meaning that any collision with the Earth would be cataclysmic.
The estimated kinetic energy of Bennu's impact with Earth is 1,200 megatons, which is roughly 80,000 times greater than the energy of the bomb dropped on Hiroshima. For comparison, the space rock that wiped out the dinosaurs delivered about 100 million megatons of energy, Live Science previously reported.
Scientists at China's National Space Science Center calculated that 23 Long March 5 rockets, each weighing 992 tons (900 metric tons), pushing against the rock simultaneously would be necessary to divert the asteroid away from a fatal course by nearly 6,000 miles (9,000 km) — 1.4 times the Earth's radius. Their calculations are detailed in a new study published in the forthcoming Nov. 1 issue of the journal Icarus.(opens in new tab)
"Asteroid impacts pose a major threat to all life on Earth," Mingtao Li, space science engineer of the National Space Science Center in Beijing and lead author of the new study, wrote in the paper. "Deflecting an asteroid on an impact trajectory is critical to mitigating this threat."
The Chinese scientists' plan would sidestep the need to stop the asteroid by more direct, yet riskier, means — like the atomic bomb method popularized by Bruce Willis in the film "Armageddon." In reality, nuking the incoming space rock would break it into multiple smaller chunks that could still collide with Earth, leading to devastating consequences.
The Chinese plan follows a similar, yet slightly more costly, past proposal made by the United States. The NASA plan, called Hypervelocity Asteroid Mitigation Mission for Emergency Response (HAMMER), would send a fleet of 30-foot-tall (9 meters) spacecraft with battering rams to bump the asteroid off course. NASA simulations suggest that 34-53 blows from HAMMER spacecraft, launched 10 years before Bennu collides with Earth, would be needed to shift the asteroid.
NASA and the ESA (European Space Agency) will be the first to test a novel asteroid nudging method in two joint missions launching November 24 of this year. The DART mission (Double Asteroid Redirection) will send a spacecraft to arrive a year later at the 7 million mile (11 million kilometer) distant Didymos asteroid system. Once there, the NASA spacecraft will slam into Didymos's moonlet — a rock in orbit around the asteroid. The ESA's mission, Hera, will then monitor how DART has budged the moonlet off-course.
Bennu is a B-type asteroid, which means that it contains high amounts of carbon and, potentially, many of the primordial molecules present when life emerged on Earth. NASA already sent a spacecraft, called Osiris-Rex, in pursuit of samples from the asteroid. Osiris-Rex arrived above Bennu in October 2020, floating above it for long enough to collect loose pieces from its surface with its 10-foot (3 m) arm. Osiris-Rex is expected to return to Earth with its spoils in 2023.
Long March 5 rockets are the workhorses of China's space program, completing most of the deliveries to China's space station and launching Chinese probes to Mars and the moon. The rockets have caused concern in the past due to their uncontrolled reentry to Earth. In May, the 22-ton (20 metric ton) section of a Long March 5 rocket fell to Earth, either burning up or landing in the sea near the Arabian peninsula. In May 2020, fragments from a previous March 5 rocket were believed to have crashed into two villages in the Ivory Coast.
Originally published on Live Science