A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter. The word galaxy is derived from the Greek galaktikos, meaning "milky," a reference to the Milky Way galaxy.
Beneath the Moon’s cratered surface lie networks of lava tubes and deep pits, natural caves that could shelter future lunar bases from cosmic radiation and wild temperature swings. These underground structures represent some of the most scientifically valuable areas in the Solar System, but they come with the very real challenge of simply getting there!
