Giant Jupiter has been steadily brightening, gleaming brilliantly in the constellation Gemini. This Sat., Jan. 10, it will be its most radiant as it reaches opposition, rising at sunset and setting with the rising Sun. A shining gem of this winter’s sky, Jupiter holds its place as the fourth brightest object in the sky after the Sun, Moon, and Venus.

Honoring astronomer Galileo Galilei, who first saw the four largest moons of Jupiter through a telescope, NASA named a spacecraft, Galileo, which orbited Jupiter from 1995 to 2003. The spacecraft collected the best evidence, so far, of an ocean beneath the icy surface of the Galilean moon, Europa. Europa’s intriguing surface appears to be the smoothest in the solar system. Few mountains exist, although ridges and cracks crisscross the frozen landscape suggesting that water may flow beneath the ice. Jupiter’s tremendous gravity creates tidal flexing on Europa. This is similar to the Moon’s tidal effect on Earth but with far greater intensity. Jupiter’s stretching and pulling of Europa could cause enough heat to keep its hidden oceans liquid.

To investigate the mystery, NASA has sent up the Europa Clipper with the aim of collecting direct evidence with an array of intricate instruments. Radar imaging may finally peer into the icy unknown, revealing Europa’s secrets, as radar detection once successfully peeled back the thick clouds of Venus.