Scientists may have found startling new evidence that there are huge tunnels cutting through the surface of the moon that were created by volcanoes ages ago. Researchers in Japan believe they’ve found key data through the Kaguya orbiter, a spacecraft launched in 2007 that examines and monitors the moon, that indicates that these tunnels may be similar to ones carved by volcanoes in Hawaii here on Earth.

It all started back in 2009 when the Kaguya spacecraft passed 60 miles above the Marius Hills and took a picture of a big hole. Large holes aren’t a surprise on the moon, as its surface is littered with large craters. But this hole was different.

When NASA’s Lunar Reconnaissance Orbiter swung by and snapped a picture, they examined it and determined that there were signs the hole extended eastward and westward. It also appeared to have a ceiling, which made it appear to be the mouth of a big tunnel. Such tunnels would have major implications for moon bases, as it would provide a refuge for astronauts from dangerous radiation.

“Lunar lava tubes are sub-surface tunnels on the Moon that are believed to have formed during basaltic lava flows,” reads a Wikipedia excerpt. “When the surface of a lava tube cools, it forms a hardened lid that contains the ongoing lava flow beneath the surface in a conduit-shaped passage. Once the flow of lava diminishes, the tunnel may become drained, forming a hollow void. Lunar lava tubes are formed on surfaces that have a slope that ranges in angle from 0.4–6.5°. Lunar lava tubes may be as wide as 500 metres (1,600 ft) before they become unstable against gravitational collapse. However, stable tubes may still be disrupted by seismic events or meteoroid bombardment.”