On July 23, astronomers from the ATLAS-MLO telescope at Mauna Loa, Hawaii, detected an asteroid measuring between 82 and 256 feet and traveling at a speed of 23,179 miles per hour. When they plotted its orbit, they were shocked to discover that the massive rock had already made its closest approach to Earth some three days earlier to within a mere 76,448 miles.
This near-miss, about one-third the distance between the Earth and the moon, went completely undetected. Had things gone differently and Asteroid 2017 OO1 entered the atmosphere, it potentially could have created a much larger explosion than the house-sized meteor that rocked Chelyabinsk, Russia, in February 2013. (Once an asteroid enters the Earth's atmosphere, it's called a meteor.)
New test on the horizon
In an effort to better detect and predict Near-Earth Objects (NEOs) both large and small, NASA is using the upcoming close flyby of an asteroid named 2012 TC4 to test its planetary defense network.
Making its closest approach on Oct. 12, the house-sized rock will give our planet an extremely close shave, with some estimates placing it as near as 4,200 miles. But it will miss Earth, giving NASA and a consortium of observatories, universities and labs across the globe the perfect opportunity to test their collaborative skills.
"Scientists have always appreciated knowing when an asteroid will make a close approach to and safely pass the Earth because they can make preparations to collect data to characterize and learn as much as possible about it," Michael Kelley, program scientist and NASA Headquarters lead for the TC4 observation campaign, said in a statement. "This time we are adding in another layer of effort, using this asteroid flyby to test the worldwide asteroid detection and tracking network, assessing our capability to work together in response to finding a potential real asteroid threat."
When TC4 was discovered in 2012, astronomers had only seven days to analyze it before it sped away and dropped from observation. As a result, there's some uncertainty over whether the asteroid will miss Earth by as much as 170,000 miles (two-thirds the Earth-moon distance) or take a dramatically closer approach. As it nears our vicinity, the planetary defense network will engage large telescopes to locate it and firmly establish its trajectory.
You can see a simulation of TC4's Oct. 12 approach in this video:
Learn now, save lives later
Tests such as the one in October are key to improving the only weapon that exists to counter a threat from above: reaction time. If we know in advance that the orbit of an asteroid will place it on a collision course with Earth, evacuation of the potential impact areas could save countless lives.
"This is a team effort that involves more than a dozen observatories, universities and labs across the globe so we can collectively learn the strengths and limitations of our near-Earth object observation capabilities," said Professor Vishnu Reddy of the University of Arizona's Lunar and Planetary Laboratory. "This effort will exercise the entire system, to include the initial and follow-up observations, precise orbit determination, and international communications."
Time also gives NASA the opportunity to build on its plans to come up with a way to deflect potential threats and shift their orbits. One such technique that recently moved from concept to design phase is the Double Asteroid Redirection Test (DART), a refrigerator-sized spacecraft that would ram an asteroid at high-speed and give its orbit a nudge. If performed far enough away, this small impact could alter the asteroid's trajectory safely away from Earth.
A rendering of what NASA's DART spacecraft might look like. The deflection weapon would strike an asteroid at about nine times the speed of a bullet in an effort to nudge its orbit away from Earth. (Photo: NASA)
“DART would be NASA’s first mission to demonstrate what’s known as the kinetic impactor technique — striking the asteroid to shift its orbit — to defend against a potential future asteroid impact,” planetary defense officer Lindley Johnson, who wins the best job title award, said in a statement. “This approval step advances the project toward an historic test with a non-threatening small asteroid.”
You can see an animation of DART in action in this video: