Wandering rocks in Death Valley explained

We know for decades that some large boulders wander across the flat surface of Racetrack Playa, a dry lake bed in Death Valley National Park in California, leaving behind them long furrows but without any trace of propulsion.

NASA scientist Cynthia Cheung from GSFC has may be discovered their secret.

Indeed, according to Cynthia, these rocks, some weighing some kilograms, probably glide on collars of ice forming around their base. When rain or snowmelt wets the valley, the collars should act as flotation devices, Cheung says. The boulders then slide so easily that high winds can send them scooting, improbably and beautifully, across the slick surface.