This pair of images taken one day apart by the Mars Color Imager (MARCI) weather camera on NASA's Mars Reconnaissance Orbiter reveals when an asteroid impact made the scar seen in the right-hand image. The left image was taken during Martian afternoon on March 27, 2012; the right one on the afternoon of March 28, 2012.
The dark area in the "after" image is about 5 miles (8 kilometers) wide. Observations with other cameras on Mars Reconnaissance Orbiter and with cameras on other Mars orbiters have located about 400 fresh impact craters on Mars that have been confirmed with before-and-after images. None except this one have created scars detected in images from MARCI, which is a wide-angle camera used for monitoring Martian weather. Owing to the daily pace of MARCI global coverage, this is the first impact event for which the timing has been constrained within the length of a single Martian day (about 24.7 hours).
Subsequent images from two telescopic cameras on Mars Reconnaissance Orbiter revealed craters within this impact scar that had not been present in January 2012. The largest of these craters -- 159 feet (48.5 meters) wide -- is the biggest fresh impact crater ever clearly confirmed anywhere with before-and-after images.
These two MARCI images are centered at 3.34 degrees north latitude, 219.38 degrees east longitude.
MARCI is one of six instruments on NASA's Mars Reconnaissance Orbiter. The camera was built and is operated by Malin Space Science Systems, San Diego. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.