Anomalous grooves on Phobos, the larger of the two Martian moons, are the result of debris ejected by impacts eventually falling back onto the surface to form linear chains of craters, according to a study published in the journal Nature Communications. In this image of Phobos, red arrows indicate a chain of small craters whose origin researchers were able to trace back to a primary impact at a large crater known as Grildrig. Image credit: M. Nayak...
