What is pow­er­ing the vol­ca­noes on Jupiter’s moon io?

All About Space - - Ask Space - Dr Fed­erico Tosi is a Staff Re­search Sci­en­tist at the In­sti­tute for Space Astro­physics and Plan­e­tol­ogy – Na­tional In­sti­tute for Astro­physics.

the en­ergy source that pow­ers io's vol­ca­noes lies in the tides ex­erted by Jupiter and in the slightly el­lip­ti­cal or­bit of the satel­lite. When the Voy­ager 1 space­craft ap­proached io in March 1979 the im­ages sent back to Earth re­vealed that its sur­face ap­peared dot­ted with a mul­ti­tude of vol­canic cen­tres, of which a dozen ex­hib­ited full ac­tiv­ity with tow­er­ing lava flows and plumes up to some hun­dred kilo­me­tres high.

un­der nor­mal con­di­tions the in­tense tidal forces pro­duced by Jupiter would even­tu­ally re­set the ec­cen­tric­ity of io's or­bit in a short time, mak­ing it a per­fect cir­cum­fer­ence. how­ever, the nearby satel­lite Europa has an or­bital pe­riod ex­actly twice that of io. this 1:2 res­o­nance forces io's or­bit to be slightly el­lip­ti­cal over time and leads the two satel­lites to re­new their mu­tual po­si­tion ev­ery 3.55 days – less im­por­tant is an­other 1:4 syn­chro­nism with the or­bital pe­riod of Jupiter's moon Ganymede. As a con­se­quence the Jupiter tide causes a pe­ri­odic de­for­ma­tion of the en­tire satel­lite which heats and melts its in­te­rior, pro­duc­ing in­tense vol­canic phe­nom­ena on the sur­face to such an ex­tent that io holds the record of ‘most vol­cani­cally ac­tive body of our So­lar Sys­tem’.

io is the clos­est of the Galilean moons to Jupiter

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