"Europa has the smoothest surface of any solid object in the solar system, evidence of a possible liquid ocean under its surface. Combined with its thin oxygen atmosphere, this suggests that there may be microscopic life on Europa."
- Subsurface Ocean (Speed):
"Under Europa's crust is a layer of liquid. While the surface is frozen solid at between -160 and -220 degrees Celcius, heat generated by the pull of Jupiter's other moons keeps the subsurface ocean liquid."
- Lineae (Payout):
"Lineae are fractures in Europa's crust that appear as dark red streaks on the smooth grey surface. The cause may be Europa's subsurface ocean rotating more slowly than its exterior layer because of the gravitational pull from Jupiter."
- Natural Satellites (Payout):
"Moons are defined by their orbit around larger celestial bodies. Most moons revolve around a planet, but smaller bodies can have moons, too - even particularly large asteroids."
- Speed of Light (Speed):
"The speed of light is the rate at which light and all massless particles travel through a vacuum. While it can seen instantaneous from up close, over long distances this speed limit becomes very noticeable. The theory of relativity relates to the speed of light."
- Cosmic Gravity (Payout):
"Gravity is one of the fundamental forces and key to understanding how the universe works. Using Newton's principles, astronomers can explain how stars and planets form, predict their mass and motion, and infer the existence of dark matter."
- Goldilocks Zone (Discount):
"The Goldilocks Zone, also called the Habitable Zone, is the region around a star with conditions necessary for a planet that can sustain life. Planets like Earth, with surface water and breathable atmospheres, might be found in these zones in other systems."
Europa's planetary host is Jupiter.
- Medicean Moons (Rank 5):
"Today, we call the four largest moons of Jupiter the Galilean Moons. But when Galileo first discovered them, he dubbed them the Medicean Moons after the powerful Medici family, who controlled Florence in the Renaissance."
- Once in a Blue Moon (Rank 8):
"The next mission that humans send to Europa will be called the Europa Clipper. It will look for evidence of organic molecules under the moon's surface, which could make it a candidate for human colonization."
- Europa - Real image above taken