NASA defines cosmic rays as “high-speed atomic nuclei with a wide range of energy.” These rays impact astronauts traveling outside the protection of Earth’s atmosphere and magnetic shield by acting like microscopic bullets damaging living cells.

A lava tube is a natural tunnel that forms when channels of molten lava flow solidify on the top and sides. When the eruption ends, the tube empties leaving a long narrow cave behind. Lava tubes can be found in the states of Hawaii, northern California, Washington, and Oregon in the United States as well as in Iceland, the Canary Islands, and along the East African Rift Valley.

The Tharsis Region of Mars is home to four large shield volcanoes including the largest volcano in the solar system, Olympus Mons. The Mars Reconnaissance Orbiter High-Resolution Imaging Science Experiment has captured images in this region of structures scientists suspect are skylights of lava tubes, structures commonly found in association with shield volcanoes on Earth.