Dunes on Pluto

Grains of frozen methane:

Dunes form on Pluto in the same way they do on Earth. Winds carry loose grains through the atmosphere and shape them into gently sloping peaks.

Scientists have observed dunes on other bodies in the solar system, including Mars, Venus, Saturn’s moon Titan, and even a comet called 67P/Churyumov-Gerasimenko. The planets and moon all have atmospheres that can sustain grain-sweeping winds, and the comet ejects jets of gas that, when they hit the surface at the right angle, can stir up particles and send them flying. “As long as we have something that can move particles or sand grains, then we should also have dunes,” Radebaugh says.

But scientists hadn’t expected to find them on Pluto. The dwarf planet does have an atmosphere, but it’s so thin that they didn’t think the wind there would be powerful enough to sweep the landscape into peaks and valleys. “The wind is sufficient to move the particles away, but it’s not sufficient to lift up the particles,” says Cathy Olkin, a planetary scientist at the Southwest Research Institute and a deputy project scientist for New Horizons.

To shape dunes on Pluto, the wind needs a little help from a process called sublimation. In the afternoons, when Pluto is at its warmest, sunlight gently heats up the upper layers of the surface and sends large amounts of icy particles flying into the atmosphere, sometimes at high speed.