Curiosity Plays in Sandy Martian Dunes: Photos

[slideshow 16216]

What do you see here? Just some sand? This could easily be a close-up photo of a tiny patch of beach. Or it could just be a macro image of the grains in a child's sandbox, with bucket and spade just out of shot. But it's neither. Sure, it's sand, but it's Martian sand. Think about that for a moment: We're looking at a microscopic observation of the grains of sand on another planet.

Mind-blowing.

NASA's Mars rover Curiosity, which has been exploring Mars since 2012, is currently driving up a mountain on Mars in the middle of the vast Gale Crater, seeking out evidence of past (and present) habitable environments on the Red Planet. And along the way, the awesome six-wheeled robot has encountered dark sand dunes, so mission scientists decided the rover should check out the 2-storey-high "Bagnold Dunes.

Taken on Sol 1184 of the mission (Dec. 5), this image shows a close-up of the dunes' sand grains, taken by Curiosity's Mars Hand Lens Imager (MAHLI) camera. Observations such as these help scientists understand mineral composition of sand on Mars, and how the dunes, particularly active ones like the Bagnold Dunes, evolve.

As Curiosity approached the Bagnold Dunes, mission scientists noted how dark they appeared. This image taken by Curiosity in September shows the dark dunes undulating in front of a pretty craggy series of rocky outcrops. These dunes are known to be active -- in other words, the Martian winds continue to shape them. According to orbital observations of Bagnold, the edges of the dunes are moving at a pace of around 3 feet (1 meter) per Earth year.

This observation, snapped by the rover's MAHLI camera, shows Curiosity's right-hand wheels crunching through the sand as the robot rolls onto the dunes on Dec. 3 (Sol 1182). Curiosity is no stranger to driving across sand, as it demonstrated, quite expertly, in February 2014. Blocking its path up Mount Sharp, and trying to avoid rough landscape to save its wheels from damage, Curiosity was commanded to climb over a sandy dune bridging a small valley called "Dingo Gap." Though there were obvious concerns about the rover becoming stuck in (or atop) the ridge, Curiosity breached the dune and continued with its mission.

Curiosity's instrument-laden robotic arm reaches out to the wind-rippled surface of "High Dune" to begin some close-up investigations of the sandy grains. Mission scientists also plan on scooping some of the sand to be deposited into the mission's on-board analysis suite to compare the mineral composition of this sand with samples taken over the past 3 years in Gale Crater and the lower slopes of Aeolis Mons (informally known as Mount Sharp). This observation was imaged by the rover's front Hazard Avoidance Camera (Hazcam) on Sol 1184 (Dec. 5).

At around the same time, Curiosity's Navcam looked down on the robotic arm's work area, showing stunning detail in the wind-carved sandy surface.

These 10 pockmarks in the ridge of dune sand is evidence of Curiosity using its Chemcam instrument laser. Chemcam uses a focused beam to burn away to uppermost later of material (be it rock or, in this case, a ridge of sand), turning it into a flash of plasma. As the laser pulses, the flashes are measured and their spectroscopic signature recorded to understand what the material is made of. This image was taken by the mission's Mastcam in the run up to Curiosity's dune investigation on Sol 1177 (Nov. 28).

It's amazing what a boot print (or, in the case of Curiosity, a wheel print) can tell us about the surface of an alien world. Just as Neil Armstrong's famous "One Small Step" boot print provided invaluable information about the composition of the fine regolith on the lunar surface in 1969, Curiosity's wheel tread marks are being used to reveal the "stickiness" and composition of the fine grains on these Mars dunes. By observing the "roll prints" of Curiosity, scientists can also see what kind of material lies just below the top layer. This technique was dramatically showcased after 2006 when NASA's Mars Exploration Rover Spirit suffered a jammed wheel. Though obviously a setback, the stuck wheel was dragged with the rover's adventures in Gusev Crater, creating a trough in Spirit's wake that could be studied.

This image of Curiosity's tread marks was captured by the rover's Mastcam on Nov. 28 (Sol 1174), showing a well-defined impression, just like Armstrong's boot print. Although that boot print remains frozen in place on the moon (as there's little atmosphere to erode it away), Curiosity's tracks will erode over time as these active dunes continue to be shaped by the Martian winds.