NASA explains mysterious rocks that move themselves
NASA has chosen an image of a Death Valley 'sailing stone' for its Astronomy Picture of the Day.
The mysterious stones baffled scientists for years as they seemingly moved on their own with no obvious explanation.
Sailing stones, also known as sliding rocks, baffled geologists because they move across the desert and leave long tracks without human or animal intervention, The Sun reports.
The dry lake of Racetrack Playa in California's Death Valley is famous for them.
Ice, wind and even bacteria are suspected of causing the heavy rocks to move as scientists have studied the stones and the long trails they leave behind.
NASA appears to have selected photographer Keith Burke's image of a sailing stone as it also features a Milky Way filled sky.
NASA explained alongside its chosen image: "How did this big rock end up on this strange terrain? One of the more unusual places here on Earth occurs inside Death Valley, California.
"There a dried lake bed named Racetrack Playa exists that is almost perfectly flat, with the odd exception of some very large stones, one of which is pictured here in April of 2019 beneath a dark, Milky-Way filled sky.
"Now the flatness and texture of large playa like Racetrack are fascinating but not scientifically puzzling - they are caused by mud flowing, drying, and cracking after a heavy rain.
"Only recently, however, has a viable scientific hypothesis been given to explain how heavy sailing stones end up near the middle of such a large flat surface.
"Unfortunately, as frequently happens in science, a seemingly surreal problem ends up having a relatively mundane solution.
"It turns out that in winter thin ice sheets form, and winds push ice sections laden with even heavy rocks across the temporarily slick playa when sunlight melts the ice."
So there you have it, ice and wind seems to have solved this mystery.
Last year, researchers claimed to have spotted a sailing stone track on a fossil of well-preserved dinosaur footprints that's 200 million years old.
Palaeontologist Paul Olsen of Columbia University and his team recently presented their findings about the long smear mark you can see among the dinosaur footprints, which had not really been focused on before.
This is quite remarkable seeing as the fossil has been on display since 1896.
The researchers have considered how the sailing stone would have moved among the footprints and argued that their findings could be evidence of a brief freezing period during the Early Jurassic.
This would fit in with the theory that the stones move when ice is formed if the area they're in gets flooded.
They are then thought to sail across the ice as it melts, creating a track in the mud that hardens and remains when the water evaporates.
Microbial mats and wind-generated water waves are also potential reasons for the stones moving but the researchers ruled these methods out for the ancient sailing stone.
They concluded that the ice method was more likely because the details preserved in the dinosaur footprint would not have been as intricate if microbes had been involved.