According to NASA, it appeared as a dark streak with multiple secondary craters, which was not seen in the previous CTX image. The image shows a very distinct crater rim and ejecta that is much darker than the surrounding dust-covered terrain. The distribution of the rayed ejecta suggests that the impactor struck from the west.
It is not clear what kind of object has been crashed on the Martian surface since NASA only speaks about 'An Impactor'.
Could it be a crashed UFO?
Link image: http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA19127