Mars moon mystery: Strange structures found inside ‘fearful’ Phobos
Mars Express, which is a 19-year-veteran spacecraft in orbit around Mars, came within 51.6 miles (83 kilometers) of Phobos on Sept. 22, 2022 and was able to probe beneath the moon’s surface using upgraded software on its MARSIS instrument (Mars Advanced Radar for Subsurface and Ionosphere Sounding).