The single largest known body of liquid water in the Solar System, and the leading place to look for life beyond Earth.
Every figure below is tagged with where it came from. Measured means an instrument read it on or at the body; modeled means it was computed and never directly observed.
No world off Earth is habitable — the honest habitable fraction of every surface here is zero. What can be answered is how far each one sits from Earth along the seven axes a habitat has to buy its way out of. Europa scores 60.9 out of 100, on 100% coverage of the axes. The single worst axis here is radiation (5,400 mSv/day — 818 thousand x Earth background); the one that most sets Europa apart from the other thirteen is radiation.
Shielding is mass, and mass is the single most expensive thing to move. Above roughly 1 mSv/day a surface habitat has to be buried.
Below the Armstrong limit (0.062 bar) body fluids boil at body temperature — the difference between needing a mask and needing a pressure vessel. Above 1 bar the problem inverts into containment, and Venus at 92 bar has never let a lander live two hours.
Delta-v sets what a launch costs; cruise time sets how much consumable, shielding and crew patience each kilogram of payload drags with it.
Both directions cost power continuously. A cold world burns reactor output to stay warm; a hot one has no cold sink to dump heat into at all.
Never landed on. Europa Clipper is en route to fly past it dozens of times from 2030.
Unprotected survival: Seconds from the vacuum; the surface dose is lethal in about 20 minutes.
The surface is water ice. Beneath it, magnetometer data from Galileo shows a conducting salty ocean 60-150 km deep — two to three times all the water on Earth.
The IAU has approved 129 names on Europa, each drawn from a theme the naming committee chose for this world. Every name in the scene above is one of them, placed at its catalogued coordinates.
Imagery is public-domain NASA/USGS mission data, streamed live from NASA Trek as a plate-carrée tile pyramid and draped on our own sphere — no third-party globe library and no cached copy of anyone else's map.
