Like, whatever happened to the Soviet Mars 2 mission? A few years after it was lost, people looking at Viking Orbiter images spotted what they thought might've been scraps of the lander's parachute blowing across the surface. It was later determined (with much blushing) that there was a scrap of dust floating in the TV camera vidicon tube, and for a while it happened to have a trajectory that placed it at locations in successive images that--coincidentally--appeared to be a white spot moving across the landscape. When the same speck was spotted halfway around the planet, the game was up. But it was an obscure mystery, enough so that Phil Hartmann worked it into one of his novels, and I fell for it, eagerly locating the correct Viking images and thinking I'd found the parachute...until I too found that white spot in images from far away from that location.

The point being, there are more human artifacts on Mars than landers and crash-lander craters. Airbags, parachutes, and heat shields, should all be visible from orbit at MRO resolutions.

Here are some arguments for looking: Plotting the path taken by things like parachutes that blow in the wind provides a way to chart winds, and calculate intensity from mass of the artifact and distance travelled. Scrape marks on the surface characterize the surface, as does depth of the crater produced by an impacting heat shield. Lots of little snippets of potentially useful data can be gathered by examining how human artifacts hit or scraped their way across Mars. Our artifacts are thoroughly documented, providing a calibration when they interact with Mars.