Scientists long suspected this phenomenon exists, but it was only after this study - which saw Io's atmosphere in the dark for the first time - that researchers found confirming evidence. When Io comes back into the sunlight, the freezing sulfur dioxide converts to gas once more. The sulfur dioxide envelope of gas freezes up while Io is in the shadow of Jupiter every day. Io also has a collapsible atmosphere, according to observations from the Gemini North telescope in Hawaii and the Texas Echelon Cross Echelle Spectrograph (TEXES).

This then makes its way back along Jupiter's magnetic field lines and causes lighting storms in Jupiter's upper atmosphere.Ī composite image of auroras on Jupiter, taken using the Hubble Space Telescope's Imaging Spectrograph. According to NASA, Io can develop 400,000 volts across itself, in turn creating 3 million amperes of electrical current. Io's orbit cuts across Jupiter's powerful magnetic lines of force, turning Io into an electric generator. Jupiter's moon Io may be small (roughly the size of Earth's moon) compared to the planet (more than 1,300 Earths could fit inside Jupiter), but the moon still has a mighty impact on its parent planet. Io's sulfur dioxide atmosphere is extremely thin - about one billionth the surface pressure of Earth's atmosphere, according to ESA. Patches of sulfur dioxide frost have also been spotted on the surface, along with hundreds of volcanoes. Io's surface is primarily composed of sulfur and sulfur dioxide, according to ESA. Io cannot escape this perpetual game of gravitational tug-of-war and subsequent planetary heating. If Io were Jupiter's only moon, its orbit would have likely 'settled down' into a circle a long time ago, but the ongoing, constant outward tug from Io's outer neighbors Europa and Ganymede ensure that does not happen. This movement causes Io's rocks to grind past each other, generating vast quantities of heat - 20 times more heat flow than Earth. This gravitation fluctuation creates a perpetual push and pull on the moon's interior in different directions, which causes Io's surface to bulge by as much as 330 feet (100 meters), according to NASA. But at its maximum distance, it can be as far away as 601 million miles (968 million km).Īs Io orbits Jupiter in an elliptical fashion, the strength of Jupiter's gravity on Io varies depending on how close the moon is to the gas giant. Distance from Earth: At its closest to Earth, when both Jupiter and Earth are on the same side of the sun, the distance to Io can be as little as 365 million miles (588 million km), according to the space science website The Nine Planets.Io is often referred to as a celestial body of fire and ice. But Io's volcanoes can reach 3,000 degrees F (1,649 degrees C). Temperature: Io's surface temperature averages about minus 202 degrees Fahrenheit (minus 130 degrees Celsius), resulting in the formation of sulfur dioxide snowfields.

Among the Galilean satellites, Io ranks third, behind Ganymede and Callisto but ahead of Europa, in both mass and volume. It has a slightly elliptical shape, with its longest axis directed toward Jupiter. Size: Io has a mean radius of 1,131.7 miles (1,821.3 km) making it slightly larger than Earth's moon.Io is tidally locked, so the same side always faces Jupiter. Io takes 1.77 Earth-days to orbit Jupiter. Its average orbital distance is about 262,000 miles (422,000 km). Distance from Jupiter: Io is the fifth moon from Jupiter.Age: Io is about 4.5 billion years old, about the same age as Jupiter.

Moons of jupiter tidal heating