The object was first spotted several years ago after being photographed by the HiRISE camera onboard the Mars Reconnaissance Orbiter. Could this be a sign post left over by aliens like in Arthur C. Clarke's 2001: A Space Odyssey
According to Jonathon Hill, a research technician and mission planner at the Mars Space Flight Facility at Arizona State University, who processes many of the images taken during NASA's Mars missions, the object in question is no more than a roughly rectangular boulder.
The HiRISE camera has a resolution of approximately 1 foot (30 centimeters) per pixel, (Not bad considering the 180-mile (300-kilometer) altitude) but not quite sharp enough to capture the cragginess of a mid-size boulder. "When your resolution is too low to fully resolve an object, it tends to look rectangular because the pixels in the image are squares. Any curve will look like a series of straight lines if you reduce your resolution enough," Hill says.