We keep such careful tabs on Mars that scientists have pinpointed, to the day, when a meteor smacked into the Red Planet, leaving a crater about half the size of a football field.
The meteor probably dropped in with a massive boom.
NASA's Bruce Cantor was checking out images from the daily global Mars coverage provided by MARCI, the Mars Color Imager, which monitors weather on the planet. That's when he noticed a dark spot near the equator.
After some sleuthing, he discovered that the dark spot hadn't been there on March 27, 2012. On March 28, there it was. The spot resulted from the "air burst and ground impact" of the meteor, according to NASA, and measured about 5 miles across.
Later, a higher-resolution camera focused in on the new crater.