In 2015, it was discovered that liquid water forms on the surface of Mars during its warmest summer days. However, thanks to the low atmospheric pressure, it boils away almost instantly – the boiling point of water on Mars is just 20°C. Water was, therefore, believed to play little or no role in shaping the Martian surface. However, an international team of scientists has shown that even this short-lived boiling water does have a significant geological impact. The researchers, led by Marion Massé from the Laboratory of Planetology and Geodynamics of Nantes, recreated two environments: one inside a former diving decompression chamber at Mars-like pressure, and the other in a cold chamber at terrestrial pressure. When a block of ice melted under ‘Earth’ conditions, water simply soaked into the sand. When a block of ice melted under Mars- like pressure, though, its boiling caused bubbles to be emitted which disturbed the sand, leaving a pattern of ridges like the ones seen on the surface of Mars. With saltwater, the effects were more obvious.