page_title: Extraterrestrial sky
section_title: Jupiter's moons as seen from Jupiter
hierarchical_section_title: Extraterrestrial sky / Jupiter / Jupiter's moons as seen from Jupiter
caption_attribution_description: English: This is an artist's concept of a plume of water vapor thought to be ejected off the frigid, icy surface of the Jovian moon Europa, located about 500 million miles (800 million kilometers) from the sun. Spectroscopic measurements from NASA's Hubble Space Telescope led scientists to calculate that the plume rises to an altitude of 125 miles (201 kilometers) and then it probably rains frost back onto the moon's surface. Previous findings already pointed to a subsurface ocean under Europa's icy crust.
context_page_description: In astronomy, an extraterrestrial sky is a view of outer space from the surface of a planet other than Earth.
  The only extraterrestrial sky that has been directly observed and photographed by astronauts is that of the Moon. The skies of Venus, Mars and Titan have been observed by space probes designed to land on the surface and send images back to Earth.
  Extraterrestrial skies seem to vary because of a number of reasons. An extraterrestrial atmosphere, if present, has a large bearing on visible characteristics. The atmosphere's density and chemical composition can contribute to differences in color, opacity and the presence of clouds. Astronomical objects may also be visible and can include natural satellites, rings, star systems and nebulas and other planetary system bodies.
  For skies that have not been directly or indirectly observed, their appearance can be simulated based on known factors, such as the position of astronomical objects relative to the surface and atmospheric composition.
context_section_description: Aside from the Sun, the most prominent objects in Jupiter's sky are the four Galilean moons. Io, the nearest to the planet, would be slightly larger than the full moon in Earth's sky, though less bright, and would be the largest moon in the Solar System as seen from Jupiter. The higher brightness of Europa would not overcome its greater distance from Jupiter, so it would not outshine Io. Ganymede, the largest moon and third from Jupiter, is almost as bright as Io and Europa, but appears only half the size of Io. Callisto, further out, would appear only a quarter the size of Io.
  None of the surface features on Jupiter's moons would appear as prominent as the lunar maria do when the Moon is viewed from Earth. Dark and light patches would be visible on Io's surface due to the coloration of sulfur that covers Io, and the largest volcanoes would be designated by dark points, but the lack of large, contrasting features results in a poor view of it. Europa, however, would appear as a completely featureless white disc. Even when viewed from nearby, most spacecraft images use contrast enhancements to clearly show the cracks in the Europan ice. Vague dark and light patches would be visible on Ganymede, whereas Callisto is much too distant for any features to be made out.
  All four Galilean moons stand out because of the swiftness of their motion, compared to the Moon. They are all also large enough to fully eclipse the Sun.
  Jupiter's small inner moons appear only as star-like points except Amalthea, which can occasionally appear as large as Callisto. However, they would all be brighter than any star. The outer moons would be invisible except for Himalia, which would appear as a dim, star-like point to the naked eye only under favorable circumstances.
caption: Water vapor plume on Europa (artist concept)[13]
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