Europa

Europa is the smallest and cutest of the four Galilean moons of Jupiter, she is the sixth largest moon in the system

she is slightly smaller than Earth's Moon, she is made out of silicate rock and has a water-ice crust (it could hold life on her surface), she always has cracks on her surface and has a very thin atmosphere, she has the smoothest surface of any object in the system

when she was younger than she was, something crashed into her, which led to the formation of the Pwyll crater, this resulted in massive bleeding and she went to the hospital afterwards

she always loves her feet, she keeps playing with them though, she always loves to play with people's feet

Life
there have been hypothesis that she could have an ocean underneath her surface, which could harbor extraterrestrial life, the Hubble Space Telescope has detected water plumes coming out of her just like one of Saturn's moons, Enceladus.

Orbit and Rotation
she orbits around Jupiter for three and a half days, with an orbital radius of 670,900 kilometers, like her friends, Io, Ganymede, and Callisto, she is tidally locked to Jupiter, so her face always faces him.

Physical Info
she is a little smaller than the Moon, she is the sixth largest moon in the system and the fifteenth largest object in the solar system

Structure
her skin is made out of water around 100 kilometers (62 miles) thick, a part frozen as her crust, and part as a liquid ocean underneath her ice, she has an induced magnetic field though interaction with Jupiter's magnetic field. the layer is likely a salty water ocean, she probably contains a metallic iron core

Surface features
Europa is the smoothest object in the solar system, lacking large features like mountains and craters, her equator may be covered with icy spikes called penitentes, which may be 15 meters high, she has a few craters on her, her surface is too active and too young to have craters, her current skin is about 20 to 180 million years old

Lineae
her surface is covered in a series of dark streaks crisscrossing her skin (which is the reason why she keeps bleeding), the larger bands are more than 20 kilometers (12 miles) across

Subsurface ocean
a liquid water ocean may exist beneath her surface, this ocean may host extraterrestrial life forms on her

Plumes
she keeps having water plumes popping out of her skin (water is her blood), the plumes are 200 kilometers high, such plume activity may help researchers find life on her

her tidal forces are 100 times stronger than that of the Moon.

Atmosphere
she has a very thin atmosphere that is made out of oxygen, but unlike Earth's oxygen, this oxygen is not of biological origin

Habitability
so far, we can't find life on her, but Europa is one of the most likely locations in the system for life

In fiction
her probable presence of water underneath her skin has made her a favorable location for science fiction, examples include
 * in 2010: Odyssey Two and 2061: Odyssey Three, aliens take interest to turn Jupiter into a star to kickstart their evolution
 * in Schismatrix, she is inhabited by genetically re-engineered posthumans
 * in The Forge of God, she dies after aliens killed her by destroying her and using chunks of her ice to terraform other planets
 * in Riding the White Bull, probes discover an ecosystem underneath her skin
 * in the Frozen Sky trilogy, intelligent alien life is found on her and they are older than Earth's humans
 * in the anime series Geneshaft, she is a giant computer who houses an AI called Oberus
 * in the Futurama episode "Put Your Head on My Shoulders", Fry, Amy, and Dr. Zoidberg have a picnic on her surface
 * in Voices of a Distant Star, she is visited by Lysithea, a batteship that shares the same name as one of Jupiter's moons
 * in HBO's Watchmen TV show, character Adrian Veidt is stuck on her surface
 * in Call of Duty: Infinite Warfare, the "Rising Threat" mission takes place on her
 * in Transhuman Space, if is discovered in hydrothermal vents on her, eventually, a war breaks out

Trivia

 * she has the smoothest surface of any object in the solar system