Io is one of the four Galilean moons of planet Jupiter. It is the hottest moon in the solar system, recording up to 2,600°F around its 400 volcanoes, hotter than Earth's volcanoes. Due to its proximity to Jupiter, it receives 3,600 rem of radiation a day (compared to 0.001 rem per day on Earth). This is thousands of times stronger than needed to kill a human being.

Io, along with Ganymede, Europa, and Callisto, were discovered by the Italian astronomer Galileo Galilei in 1610.

Io 4K pan-zoom image

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  Source image: NASA (Galileo)

Io facts

Designation: Jupiter I
Magnitude: 5
Mass: 8.94 x 1022 kg
Radius: 1,815 km
Density: 3.55 gm/cm3
Distance from planet: 421,600 million km
Rotational period: 1.77 days
Orbital period: 1.77 days
Orbital velocity: 17.34 km/sec
Eccentricity of orbit: 0.004
Inclination of orbit: 0.04 °
Albedo: 0.61
Atmosphere: SO2 = 90%
Temperature (mean): -183°C / 1,527°C

Io volcanic features

Io has hundreds of volcanoes, patera (large caldera or volcanic craters), and lava flows on it's surface. There is believed to be a sulfur magma ocean beneath it's surface that feeds the volcanoes, with temperatures of 2,420°F during eruption.

Io flux tube & plasma torus

Io's volcanoes eject plumes of sulfur into space that become ionized as Io moves through Jupiter's magnetosphere, forming the Io plasma torus. This gigantic torus is filled with sulfur and oxygen ions that have a temperature of about 1 million °C / 1.8 million °F.

As Io orbits around Jupiter inside the plasma torus, electrical currents are generated from the surface of Io to the north and south poles of Jupiter, forming aurorae. This current flow "channel" is called the Io flux tube, and generates 5 million amps at 400 volts, producing 2 trillion watts of power.

Here are the major volcanic features of Io.

Ah Peku Patera caldera
Amaterasu Patera caldera
Amirani volcano
Asha Patera caldera
Babbar Patera caldera
Culann Patera caldera
Dazhbog Patera caldera
Emakong Patera caldera
Estan Patera caldera
Fuchi Patera caldera
Gish Bar Patera caldera
Hi'iaka Patera caldera
Itzamna Patera caldera
Kami-Nari Patera caldera
Kinich Ahau Patera caldera
Loki volcano
Loki Patera caldera
Malik Patera caldera
Manua Patera caldera
Masubi volcano
Maui Patera caldera
Mithra Patera caldera
Monan Patera caldera
Pele Patera caldera
Pillan Patera caldera
Prometheus volcano
Prometheus Patera caldera
Pyerun Patera caldera
Ra Patera caldera
Reiden Patera caldera
Shamash Patera caldera
Shango Patera caldera
Surt volcano
Svarog Patera caldera
Tawhaki Patera caldera
Thomagata Patera caldera
Thor volcano
Tupan Patera caldera
Tvashtar Patera caldera
Viracocha Patera caldera
Zal Patera caldera
Zamama volcano

And now I see with eye serene, The very pulse of the machine. A being breathing thoughtful breaths, A traveler between life and death.

- William Wordsworth / Love, Death & Robots (Netflix)