Todays Image of Mars shows a portion of a well preserved 6 to 7km crater imaged by HiRISE. A well preserved crater is one that has a sharp crater rim, deep essentially unfilled cavity, and small impact features preserved. A well preserved crater will also have few, if any superimposing features like subsequent impact craters or lava flows.
Scientists are interested in well preserved craters because they're oftentimes relatively recent and reveal active processes, like gully formation, boulder faults, and slope streaks. Being able to see these ongoing processes helps scientists to better understand the environment on Mars and allows them to better predict what will happen when an asteroid impacts.
These predictions may be extremely helpful in the future if one of our rovers is sent to explore a recent impact crater. Knowing what to expect could ensure that future missions go smoothly and aren't disrupted by an unforeseen change to the structure of a crater, etc.
Not only can studying active craters teach scientists about active processes on Mars, but they can sometimes reveal ice or water that was just below the surface. Discoveries like this can completely revolutionize our understanding of the past Martian climate and help scientists plan future manned missions to Mars, where water will be critical.
Clicking on this image will take you to the original, captioned image from HiRISE.