bridges have been found on the moon for the first time in images taken by a high-resolution camera aboard NASA’s Lunar Reconnaissance Orbiter.
Students scrutinising the camera’s images have spotted two natural bridges on the moon’s far side. The larger bridge measures 20 metres long and 7 metres wide, while its smaller neighbour is about half that size.
Unlike natural bridges on Earth, which form largely by erosion from wind and water, these lunar bridges probably formed as a result of an impact in the last billion years, says Mark Robinson, a planetary geologist at Arizona State University in Tempe and principal investigator for LRO’s camera.
The impact melted the surface that it hit and gouged out a 77-kilometre-wide basin known as King crater. Some of the melted rock splashed over the crater’s rim, forming a fiery pool of liquid 17 kilometres across just outside the crater’s northwest rim.
Like the skin that forms on top of cooked pudding, the surface of this “melt pond” formed a crust as it cooled, while the interior remained molten for longer. As the ground shifted after the impact, the molten interior likely flowed downhill, leaving behind unsupported crust that collapsed in two places, creating a natural bridge.
The rocky arches are probably strong enough to support an astronaut, Robinson says, but since the US no longer aims to return people to the moon, it may be a while before we know for sure. “If you can arrange for me to go, I would be delighted to go test its strength out,” he says. “I would walk out and jump on it.”