Curiosity has discovered on Mars a landscape covered with small polygonal fractures, resembling a giant honeycomb.
These types of structures are generally cracks of dried mud, but several mechanisms can produce them. The rover's measurements will therefore need to determine whether this new field truly preserves traces of ancient wet episodes.
A close-up of the polygonal fractures discovered by NASA's Curiosity rover on Mars.
NASA/JPL-Caltech/MSSS
The rover encountered these shapes while climbing a valley of Mount Sharp named Valle Grande. Each polygon measures about 4 to 8 centimeters across. Curiosity had already observed small comparable areas, but never such a vast expanse: the patterns extend in all visible directions and even climb the flanks of a nearby butte.
The polygonal fractures can appear when wet mud contracts as it dries, then possibly during new wetting cycles. However, heat and cold can also crack rock. Another possibility is the compression of buried sediment, which expels its water.
The geological context makes this research particularly interesting. Billions of years ago, lakes and streams occupied the lower foothills of Mount Sharp, which Curiosity has been climbing since 2014. The rover has found chemical traces of this watery history, as well as carbon molecules that may predate the formation of RNA and DNA.
These molecules are not, however, proof of Martian life. Geological processes can produce the same compounds, and no biological origin has been established. They only show that ancient Mars brought together water, nutrients, and chemistry compatible with a habitable environment for microbes.
Curiosity, which arrived in August 2012, is thus continuing a long-term quest rather than a direct search for organisms. The new polygon field adds a site where the chemistry, texture, and stratigraphy of the rocks can be compared.