Cold as ice

Then theres a whole other type of volcanism, called cryovolcanism. As NASA explains in this interactive graphic, cryovolcanoes erupt water and gases rather than melted rocks. They dot a number of different bodies in our solar system, include Neptunes moon Triton and Saturns moon Enceladus.

Its a form of volcanism because volcanism is a process that brings material from the interior to the surface, but it is not molten rock, Dr. Rosaly Lopes, Senior Research Scientist at NASAs Jet Propulsion Laboratory, told Astronomy. Instead, cryovolcanoes occur on bodies with an ocean situated beneath an icy crust. When pressure builds up, it is released in the form of geysers of water mixed with ammonia or methane.

Generally, cryovolcanoes are found on bodies in the outer solar system, Lopes said, though scientists also believe that cryovolcanism may even have happened on the asteroid / dwarf planet Ceres. According to recent studies from the Max Plancke Center for Solar System Research, several structures in Occator Crater suggest recent geologic activity consistent with cryovolcanic activity, though to date only one mountain has been found on the world.

Information about these volcanoes provides scientists with clues about important geological processes. Volcanism is one of the major, really fundamental processes that shapes the surface of a planet or moon, Lopes said. That shape, she explained, comes from the interplay of four major processes volcanism, tectonism, erosion, and impact cratering. Understanding volcanisms role in shaping a bodys surface provides a crucial clue in understanding more about the geological processes of that planet.

For example, Lopes told Astronomy, if Earth was the only place we had seen volcanism, we might think that volcanism really depends on plate tectonicsBut when we look at the other planets, we see that they have or have had volcanism in the past, and there is no plate tectonics.

She cited Io as one instance of this: when scientists saw the incredibly active volcanism occurring there, they realized that it was tidal heating that caused this volcanism. It works like this: Io and other Galilean satellites (such as Europa and Ganymede) are in synchronous rotation around Jupiter. Io then becomes caught up in a tug of war between Jupiters gravity and the gravity of these other satellites, Lopes explained. This in turn leads to the bulging of Ios crust up and down, and the resulting friction produces a large amount of heat and a molten interior. When the pressure builds, it occasionally erupts melted rock and plumes of gas.

Recent evidence even suggests that they may appear on comets. Comet 29P/Schwassmann-Wachmann displays outbursts on carbon monoxide consistent with other forms of cryovolcanism around the solar system. The outbursts seem to happen from one spot on the comet making it one of the smallest bodies believed to have signs of volcanism.

While volcanoes can shed light on certain geological processes, theres another, even more intriguing reason to search for them: they may be indicators of climates suitable for life. Volcanism provides heat and energy, which is essential for life, Lopes said. And cryovolcanism has not only heat, but watertwo of the essential ingredients of life. That doesn't mean that every body with cryovolcanism has the necessary conditions to support life, of course. But those planets may not be a bad place to start.

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Planetary scientists are turning up volcanoes everywhere they look - Astronomy Magazine