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Jupiter's IO Moon

Jupiter's moon IO
Jupiter's moon IO

IO is one of planet Jupiter’s moons. It was discovered on January 8, 1610 by Galileo Galilei. This discovery along with Jupiter’s other Galilean moons (Ganymede, Europa, Callisto) had great significance because it was the first time it was observed a moon orbiting another planet than Earth. This helped understand that planets in our solar system orbit the Sun, rather than everything orbits the Earth. Galileo originally named IO “Jupiter l” (number 1) since he just used numerical values 1 to 4 for the moons. It wasn’t until about 250 years later that the moon “Jupiter l” was named IO, which was named from Greek mythology.

IO Moon's area Tvashtar Catena
IO's Tvashtar Catena area

IO’s distinctive characteristic in our solar system is its volcanic activity. Just to give you a sense of how volatile it is, imagine the Earth’s ocean with waves as high as 100m (328 ft), but wait, imagine that happening with a solid surface. That is what is occurring on IO due to the moons Europa and Ganymede causing IO to orbit in an irregular orbit around Jupiter.

IO is the 3rd largest moon of Jupiter with a diameter of 3,643.2 km (2,264 mi) which is 1.05 times larger than Earth’s moon. The volume is 25,319,064,907 km3 (6,074,366,681 mi3) which is 1.15 times more than Earth’s moon. The surface area is 41,698,064.74 km2 (16,099,712.8 mi2) which is 1.1 times more than Earth’s moon. The mass is 8.9319 x 1022 kg which is 1.22 times more than Earth’s moon.

IO is the 5th moon from Jupiter with an average orbit distance of 421,800 km (262,094 miles) which is 1.1 times farther than Earth and its moon. The closest (Perigee) point during IO’s orbit is 420,071 km (261,020 miles) and farthest (Apogee) is 423,529 km (263,169 miles). The orbit inclination to ecliptic (orbit angle relative to Jupiter’s equator) is 0.036° with an orbit eccentricity (amount of deviation from a perfect circle) of 0.0041. IO’s orbital period (time for 1 trip around Jupiter) is 1.769 Earth days travelling at a velocity of 62,423.1 km/h (38788 mph) and has the exact same rotation period (time for 1 rotation) of 1.769 Earth days. This is the reason why the same side of IO always faces Jupiter. To visualize this, just hold your arm straight in front of you with a ball in your hand and make a full turn in 1 spot. Obviously the same side of ball will always be facing you since for every degree you turn, then so does the ball. It must also be noted that during IO’s orbit is crosses Jupiter’s powerful magnetic force in that time 66 tons of IO’s material is stripped away every minute. Some of this material goes to Jupiter and creates auroras.

IO has a surface gravity of 1.796 m/s2 (5.89 ft/s2) which is slightly more than Earth’s Moon surface gravity. That means it would take about 5.8 seconds to drop a solid ball from a 10 story building, where on Earth it would be about 2.5 seconds. IO’s escape velocity is 8,552 km/h (5,314 mph) which is the same as Earth’s moon escape velocity.

IO has a great variance of temperature depending where you are. If you are near the volcanic areas then you will enjoy 1,649°C (3000°F) of heat. However if you are anywhere else you will enjoy a chilling temperature of -130°C (-202°F). This range of temperature is a reason why the atmosphere is Sulfur Dioxide. As you go deeper the outer shell of IO is silicate and the core is iron, which may give it a magnetic field of its own, but that is still a mystery.