Astrophysics (Index)About

supercritical fluid

(state of matter at sufficient pressure and temperature)

Supercritical fluid (not the same thing as superfluid) is a state of matter (as is "solid", "liquid", "gas") which requires a certain temperature and pressure (in many cases, substantial), the minimum amount of the two (termed the critical point, which is different than the triple point) depending upon the substance. The state has some characteristics of a liquid and some of a gas:

The supercritical fluid state is of interest to planetary science, especially within the solar system where its presence is evident: the gravity of Saturn and Jupiter give them the internal pressure to produce supercritical hydrogen through much of their interior; this alone is sufficient mass that most of the matter in the solar system excluding the Sun is in the supercritical-fluid state. Uranus and Neptune also many have internal supercritical fluid, and Venus's high-pressure atmosphere might.

Further reading: