Like many of the solar system’s rocky objects, Earth bears the scars of past asteroid impacts—including some wallops that shaped the arc of life itself. Some 66 million years ago, for instance, a six-mile-wide asteroid slammed into Earth near Mexico’s Yucatán Peninsula, triggering a mass extinction that wiped out the non-avian dinosaurs.

Now for the first time in our planet’s history, Earth is going to hit back.

At 10:21 p.m. Pacific Time on November 23, a NASA mission called DART (Double Asteroid Redirection Test) launched from Vandenberg Space Force Base, California, to embark on a nearly year-long voyage around the sun. If all goes well, DART’s journey will end on the evening of September 26, 2022, when the golf cart-size spacecraft will