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Most of us have seen a movie featuring the threat of Earth’s destruction by an incoming asteroid. Some movies describe the extinction of the dinosaurs, but others take an often all-too-realistic look at what could happen to our planet if an asteroid were to collide with it—with humans on it. In real life, NASA has been working to test a potential defense strategy should this threat ever materialize. And the successful completion of this test last week on Monday, September 26, marks a thrilling acknowledgment of our potential to protect our planet from such threats.
To manage its ongoing efforts to defend the planet against asteroids and comets that orbit the Sun like planets, or near-Earth objects (NEOs), NASA established the Planetary Defense Coordination Office (PDCO) to manage its ongoing mission of planetary defense.
The PDCO provides many services to NASA, including early detection of potentially hazardous objects (or PHOs), which are a subset of NEOs with orbits predicted to come within 5 million miles of Earth’s orbit and of a diameter large enough to damage Earth’s surface (30 to 50 meters). It also tracks and characterizes PHOs and issues warnings of the possible effects of potential impacts; studies strategies and technologies for mitigating PHO impacts; and works to coordinate US government planning for response to an actual impact threat.
During NASA’s Double Asteroid Redirection Test (DART), a spacecraft was directed at a pair of asteroids as a test of technology. DART targeted the asteroid moonlet Dimorphos, a small body just 530 feet (160 meters) in diameter. It orbits a larger, 2,560-foot (780-meter) asteroid called Didymos. Important note: DART’s target asteroids are not a threat to Earth. "There is no scenario in which one or the other body can become a threat to the Earth," says Thomas Zurbuchen, associate administrator at NASA. "It's just not scientifically possible, just because of momentum conservation and other things."
The asteroid pair was situated 7 million miles from Earth, requiring a global team using dozens of telescopes stationed around the world and in space to observe the asteroid system. Together they guided the 1,260-pound box-shaped spacecraft through the final 56,000 miles of space into Dimorphos, intentionally crashing into it at roughly 14,000 miles per hour, successfully slowing the asteroid’s speed. Ultimately, the mission’s one-way trip confirmed that NASA can navigate a spacecraft to intentionally collide with an asteroid with the goal of deflecting it, a technique known as kinetic impact.
According to NASA Administrator Bill Nelson, “DART represents an unprecedented success for planetary defense, but it is also a mission of unity with a real benefit for all humanity. . . . [T]his international collaboration turned science fiction into science fact, demonstrating one way to protect Earth.” Over the coming weeks, NASA will precisely measure Dimorphos’ orbital change to determine how effectively DART deflected the asteroid. The results will help validate and improve scientific computer models designed to predict the effectiveness of this method as a reliable strategy for asteroid deflection.
All of this is to say that depictions of Earth’s fate as resting in the hands of some very expediently working astronauts may not factually represent the future of asteroid deflection. In fact, science aims to be able to identify potential threats from asteroids whose course doesn’t lead to an impact with Earth for decades—maybe even centuries. And while that doesn’t make for very exciting cinema, it does make for a much safer future for humankind.
Check out images from DART immediately prior to impact here.
Also, Google “Nasa DART Mission” for a clever Google tribute to the mission’s success.