Jupiter’s satellite Callisto shines brighter than the moon[김정욱의 별별이야기](55)

■Can be observed from Earth using an astronomical telescope
■The possibility of life is very low.

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Callisto. Photo provided by National Aeronautics and Space Administration (NASA)

Jupiter’s satellite, ‘Callisto’, is one of the Galilean satellites (Jupiter’s four major satellites discovered by Galileo Galilei: Ganymede, Io, Europa, and Callisto). Callisto, one of the largest satellites of the solar system, has a diameter of 4821 km, which is larger than Earth’s moon.

This satellite can be observed from Earth through astronomical telescopes and shines brighter than the moon. Its surface is made of rock and ice, and like Jupiter’s other moons, many craters (huge pits created on the surface of the celestial body due to massive impacts such as volcanic eruptions, meteorite impacts, or nuclear explosions) are found. Carlitos’ crater is nearly saturated.

The average temperature of Carlitos is -139 degrees, the lowest is -193 degrees, and the highest is -108 degrees, making it a cold celestial body like other Galilean satellites.

Since the late 1990s, hypotheses have emerged that an ocean may exist beneath the surface of Callisto. Additional research later found that Jupiter’s magnetic field did not penetrate Callisto. Additionally, it was discovered that there is a conductive fluid inside Callisto, leading to the hypothesis that this fluid is an ocean containing ammonia and salt.

Even if there is an ocean under the ice, the probability of life being there is low due to the weak heat inside. Perhaps because there is little possibility of habitability, this satellite has not received much attention from space scientists.

Callisto is the outermost of the four Galilean moons that orbit Jupiter. It orbits Jupiter at a distance of 1.88 million km.

Callisto has a very weak atmosphere composed of carbon dioxide. The atmosphere is mostly carbon dioxide, but there is also some oxygen.

The atmosphere here is so thin that it disappears within 4 days after its creation, and scientists speculate that carbon dioxide that sublimates slowly from the ice crust continuously replenishes the atmosphere.