# Liquids/Liquid objects/Io

The image at right is a "global view of Jupiter's moon, Io, ... obtained during the tenth orbit of Jupiter by NASA's Galileo spacecraft. Io, which is slightly larger than Earth's moon, is the most volcanically active body in the solar system. In this enhanced color composite, deposits of sulfur dioxide frost appear in white and grey hues while yellowish and brownish hues are probably due to other sulfurous materials. Bright red materials, such as the prominent ring surrounding Pele, and "black" spots with low brightness mark areas of recent volcanic activity and are usually associated with high temperatures and surface changes. One of the most dramatic changes is the appearance of a new dark spot (upper right edge of Pele), 400 kilometers (250 miles) in diameter which surrounds a volcanic center named Pillan Patera. The dark spot did not exist in images obtained 5 months earlier, but Galileo imaged a 120 kilometer (75 mile) high plume erupting from this location during its ninth orbit. North is to the top of the picture which was taken on September 19, 1997 at a range of more than 500,000 kilometers (310,000 miles) by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft."
At volcanic locations, native liquid sulfur can be seen flowing, such as in the image second down on the right, and it is red.

## Liquids

Europa is tidally locked to Jupiter, with one hemisphere of Europa constantly facing Jupiter, as such, there is a sub-Jovian point on Europa's surface, from which Jupiter would appear to hang directly overhead with Europa's prime meridian passing through this point.
The tidal locking may not be full, as a non-synchronous rotation has been proposed: Europa spins faster than it orbits, or at least did so in the past. This suggests an asymmetry in internal mass distribution and that a layer of subsurface liquid separates the icy crust from the rocky interior.
The orbital eccentricity of Europa is continuously pumped by its mean-motion resonance with Io. Thus, the tidal flexing kneads Europa's interior and gives it a source of heat, possibly allowing its ocean to stay liquid while driving subsurface geological processes. The ultimate source of this energy is Jupiter's rotation, which is tapped by Io through the tides it raises on Jupiter and is transferred to Europa and Ganymede by the orbital resonance.
It is estimated that Europa has an outer layer of water around 100 km (62 mi) thick; a part frozen as its crust, and a part as a liquid ocean underneath the ice. Recent magnetic-field data from the Galileo orbiter showed that Europa has an induced magnetic field through interaction with Jupiter's, which suggests the presence of a subsurface conductive layer. This layer is likely to be a salty liquid-water ocean. Portions of the crust are estimated to have undergone a rotation of nearly 80°, nearly flipping over, which would be unlikely if the ice were solidly attached to the mantle. Europa probably contains a metallic iron core.

## Liquid objects

A liquid is made up of tiny vibrating particles of matter, such as atoms and molecules, held together by intramolecular bonds. Although liquid water is abundant on Earth, this state of matter is actually the least common in the known universe, because liquids require a relatively narrow temperature/pressure range to exist.
The first image at right shows liquid water using an infrared detector, but information confirming the presence of liquid water solely from the infrared image is inferred.
The image at left uses a visual radiation detector to record a meteor collision with liquid water.
Reconstructions of seismic waves in the deep interior of the Earth show that there are no S-waves in the outer core. This indicates that the outer core is liquid, because liquids cannot support shear. The outer core is liquid, and the motion of this highly conductive fluid generates the Earth's field (see geodynamo).
"When solid or liquid objects formed in the early Solar System, either by condensation from the vapor phase or by melting and crystallization of preexisting material, each of these isotopic chronometers is expected to have been reset."

## Astrognosy

A model for the internal structure of Io shown on the right includes an ultramafic mantle and an iron and iron sulfide core.

## Hypotheses

* Europa is a solid ice ball.