The space agency plans to ‘on-contact’ the small rock about 120 million miles from Earth when it is about to strike in the early morning hours in November
In the early morning hours of 26 November, 2019, an object with a diameter of about 1m will crash into a deep space asteroid known as Bennu. Known as a kinetic impactor, the 3ft-thick (1m) shell of titanium and aluminum plunges into the surface of the plump rock, one of the largest on Earth. But don’t panic – scientists say it will bring about a near-term “tipping point” that will detonate a 25kg (55lb) “super glancing punch” at Bennu, which could send it hurtling toward Earth in 2135, and possibly send it off course for a close call.
Before Bennu can reach its potential comet-like destiny, the Space Launch System (SLS) rocket it is destined to fly on, and the Space Launch Ground Control Control Area in California, will “on-contact” the rock about 120 million miles from Earth (eliminating any deliberate attempt at landing on the rock), approximately 120 seconds before the impact.
The spacecraft will release its charged particle shakedown projectile from the rocket’s underside, after which it will be cut loose about 12 miles above the surface, where it will burst into a fireball and spray the asteroid with thousands of chunks the size of microwave ovens. One cubic mile of debris will be ejected, enough to create a crater about 4 miles wide and about 50 feet deep.
“Everybody was incredibly excited,” said Roger Clark, an engineer at the Aerospace Corporation who helped design and refine the spacecraft’s touch-and-go launch abort system. “We were trying to time it so that we would ‘impact’ on the rim of this asteroid’s atmosphere. It looks as if the splashdown is going to be later, but I expect a bang when we do hit.”
Bennu is a golf-cart-sized rock that rose to prominence in early 2016, when scientists discovered that it was there, after surveying hundreds of near-Earth asteroids every month for a decade. Their discovery boosted concerns about their dangerous threat, and ignited a firestorm in Congress over how to prevent one from crashing into Earth.
It was, in fact, a lower-priority to space scientists than an asteroid named 2012 TC3, which emerged from the solar system’s dawn and smashed into Earth’s atmosphere in 2012.
An artist’s concept of the Space Launch System rocket and the Space Launch Ground Control Area, where the spacecraft will be installed. Photograph: AVEO/Tom Graham/Courtesy The Aerospace Corporation
The asteroid-destroying “crisis asteroid” nickname, however, has stuck.
“Bennu, in itself, was not a threat,” said David Kelly, lead scientist of the planetary defense initiative at NASA. “That difference will be short-lived.”
At that point, Kelly said, NASA’s extensive data would show whether Bennu posed a direct threat. He said space agencies around the world, including Japan and China, had already begun plotting their orbits around the asteroid. The United States government has allocated $59m to the project, and the agency has a space mission budget set at $20.2bn over the next six years.
These efforts are helping NASA and other space agencies figure out how to avoid another 6,000-mile collison. The United States Air Force’s Strategic Command, which monitors hostile space objects, is already set up to set off an impactor of its own if it were to dash toward Earth.
“The idea here is to reduce the cost, probability of collision, and opportunity costs,” said Clark, whose firm, ESAX, is working with NASA on the Bennu project. “The target of the impactor is a so-called ‘dark outlier’ which is literally more dangerous than the surrounding population of asteroids that have been analyzed to date.”
When Bennu’s impactor directly hits the rock, it will be focused by NASA’s Deep Impact spacecraft, and by a sensor on the SLS rocket. The test is critical to NASA’s ability to conduct a more ambitious crash in 2028, when the space agency plans to use its Deep Impact spacecraft to “contact” asteroid 2018 AJ49, which is about 70m wide and not yet close enough to Earth.