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[[Image:Gal io3 48584.jpg|thumb|250 px|left|Sodium cloud released by volcano Prometheus on Io]]The tremendous observed flexing during a sidereal month of less than two Julian days would be expected to heat the mantle tremendously. In fact, Io is known to radiate heat at a power level of about 125 TW on average. This yields a heat flow per surface area of 2.5 W/m².<ref name=solarviews2/>

[[Image:Gal io3 48584.jpg|thumb|250 px|left|Sodium cloud released by volcano Prometheus on Io]]The tremendous observed flexing during a sidereal month of less than two Julian days would be expected to heat the mantle tremendously. In fact, Io is known to radiate heat at a power level of about 125 TW on average. This yields a heat flow per surface area of 2.5 W/m².<ref name=solarviews2/>

Yet the tremendous heat of Io's volcanoes is not fully understood or explained. If uniformitarian theories are correct and Io is millions of years old, the innumerable tidal-flexing cycles should have lowered Io's melting point so that it would not produce such hot lava flows. The high temperatures observed are in fact consistent with basaltic lava flows that most uniformitarians think occurred billions of years ago on [[Earth]]. No volcano on Earth today is as hot as are some of the volcanoes now on Io.<ref name=Phillips>Phillips, Tony. "[http://science.nasa.gov/newhome/headlines/ast04oct99_1.htm Io's Alien Volcanoes: Galileo Heads for a Sizzling Encounter]." ''Space Science News'', October 4, 1999. Accessed February 18, 2008.</ref>

Yet the tremendous heat of Io's volcanoes is not fully understood or explained. If uniformitarian theories are correct and Io is millions of years old, the innumerable tidal-flexing cycles should have lowered Io's melting point so that it would not produce such hot lava flows. The high temperatures observed are in fact consistent with basaltic lava flows that most uniformitarians think occurred billions of years ago on [[Earth]]. No volcano on Earth today is as hot as are some of the volcanoes now on Io.<ref name=Phillips>Phillips, Tony. "[https://science.nasa.gov/newhome/headlines/ast04oct99_1.htm Io's Alien Volcanoes: Galileo Heads for a Sizzling Encounter]." ''Space Science News'', October 4, 1999. Accessed February 18, 2008.</ref>

=== Mountains ===

=== Mountains ===

== Problems for Uniformitarianism Posed by Io ==

== Problems for Uniformitarianism Posed by Io ==

* Io is radiating more heat than [[tidal heating]] could generate. Therefore Io must have another source of heat, or else the observed heat flow is unusually high and not something that Io could maintain for long.<ref name=Arnett/> And even in the latter case, stating that the current heat flow is unusual begs the question of what drove the heat flow to present levels.

* Io is radiating more heat than [[tidal heating]] could generate. Therefore, Io must have another source of heat, or else the observed heat flow is unusually high and not something that Io could maintain for long.<ref name=Arnett/> And even in the latter case, stating that the current heat flow is unusual begs the question of what drove the heat flow to present levels.

* As mentioned before, the volcanic eruptions on Io have one-third the absolute temperature at the surface of the [[Sun]]. This defies explanation, because according to all current uniformitarian theories, Io's mantle ought to melt at far lower temperatures after millions of years of constant reworking by tidal flexes.<ref name=Phillips/>

* As mentioned before, the volcanic eruptions on Io have one-third the absolute temperature at the surface of the [[Sun]]. This defies explanation, because according to all current uniformitarian theories, Io's mantle ought to melt at far lower temperatures after millions of years of constant reworking by tidal flexes.<ref name=Phillips/>

The [[Galileo Project]] spacecraft did not make any close passes at Io for years, primarily because mission controllers were concerned with the safety of the spacecraft and desired to examine several far less dangerous targets. The mission was extended twice, however, and in the last years of the mission, ''Galileo'' made several flybys of Io and took surface temperature measurements. These measurements clearly showed that Io's volcanoes tended to be hotter even than many volcanoes on Earth.

The [[Galileo Project]] spacecraft did not make any close passes at Io for years, primarily because mission controllers were concerned with the safety of the spacecraft and desired to examine several far less dangerous targets. The mission was extended twice, however, and in the last years of the mission, ''Galileo'' made several flybys of Io and took surface temperature measurements. These measurements clearly showed that Io's volcanoes tended to be hotter even than many volcanoes on Earth.

In September 2003, the Galileo controllers deliberately crashed the spacecraft on Jupiter, in order to avoid crashing it on [[Europa]] and possibly doing irreparable damage to Europa's subsurface ocean. Since that time, observations have been limited largely to Earth-based telescopes (like the Keck Observatory in [[Hawaii]] and the [[Hubble Space Telescope]]—except that the [[New Horizons mission]] made a flyby of Io on February 28, 2007, and captured many remarkable images. No other missions to Io are planned for at least ten more years.

In September 2003, the Galileo controllers deliberately crashed the spacecraft on Jupiter, in order to avoid crashing it on [[Europa]] and possibly doing irreparable damage to Europa's subsurface ocean. Since that time, observations have been limited largely to Earth-based telescopes, like the Keck Observatory in [[Hawaii]] and the [[Hubble Space Telescope]].  The [[New Horizons mission]] also made a flyby of Io on February 28, 2007, and captured many remarkable images. No other missions to Io are planned for at least ten more years.

==References==

==References==