NASA/JPL/University of Arizona

Rocks and waves of sand dominate this image of Mars from the HiRISE camera. However, some find an mysterious rectangular-shaped boulder sticking out of a hillside.

Explore the rugged terrain of Mars starting in the area of the enigmatic, rectangular boulder. What shapes and stories do you see in the sands of Mars? Leave a note below.

If you look around the boulder-field at the bottom of this hillside, you’ll find lots of shadows that are rectangular looking. But are they all “monoliths” placed by aliens similar to those created by Arthur C. Clarke in his story “The Sentinel” and popularized in the Stanley Kubrick film “2001: A Space Odyssey?” The answer lies probably in the play between shadows and image resolution. Pixels on images are square. If you look really close at the monitor you are using you’ll find a rectangular grid of glowing square pixels make up the text and images on this screen. The HiRISE camera has a resolution of about 30 centimeters. That means that one pixel equals about 30 centimeters or about one foot. That’s only about the size of a beach ball. Big boulders become square-like objects; shadows become square-like as well. An early morning or late afternoon sun creates long shadows making objects appear larger than they really are. Very similar to walking down a road with your back to the Sun at sunset and seeing your shadow stretch out tens of feet in front of you.

You can read more about this effect in a post at Life’s Little Mysteries.

The more interesting stuff in this image are the ripples of sand that drift across the plateau craters and then march along the bottom of the canyon at the bottom of the image. Sand has nearly filled in the double craters in the center of the image creating a pie-shape. Geologists find this image interesting because of the layers of rock that make up the wall of the canyon.

Launched with Mars Recon­nais­sance Orbiter, or MRO, in 2005, HiRISE is one of six instru­ments aboard the spacecraft orbiting Mars. HiRISE’s cam­era can see objects on the sur­face as small as a beach ball. The instru­ment can also offer scientists stereo views of the surface.

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