The Curiosity Mars rover has detected distinctive hexagonal mud cracks that scientists think could be the first evidence of wet-dry cycles on Mars. One of the common theories of how life began on Earth is that continuous cycles of wet and dry conditions on land helped initiate the complex chemical building blocks necessary for microbial life.

Curiosity detected these mud cracks as it ascended through the sedimentary layers of Mount Sharp, in a transition zone between a clay-rich layer and a rich saline mineral zone higher up. Transitional zones provide records showing when long dry periods became common and rivers and lakes began to recede. The hexagonal patterns appear as the mud dries, shrinks and breaks into T-shaped joints. When the joints are repeatedly exposed to water, the T-joints soften and become Y-shaped, eventually forming hexagons.

Mars is no stranger to rifts large and small. The Valles Marineris canyon system, seen in the first image taken by Viking Orbiter 1, is 2,000 miles (3,000 km) long, 370 miles (600 km) wide and 5 miles (8 km) deep.

Scroll to see mud cracks, the first evidence that ancient Mars had regular wet-dry cycles like Earth.

About the photos

Photo 1: A mosaic of Mars shows the red planet almost fully illuminated in the darkness of space. A large canyon stretches across the planet's surface near the centre of the photo. Mars is in shades of brown and red and contains some black spots.

Photo 2: A zoomed-in image of the Martian surface shows preserved ancient mud cracks believed to have formed during long cycles of wet and dry conditions over many years. This image, taken by the Curiosity rover, shows encrusted, almost scale-like hexagonal shapes all over the dark beige surface.

 

Source: nasa.gov