Earth does not offer the unique privilege in our solar system of being able to admire a colorful aurora. American astronomers discovered that there is a visible aurora on all four of Jupiter’s large moons: Io, Europa, Ganymede and Callisto. It is the first time that auroras have been discovered on the last two, while new features of the impressive atmospheric phenomenon have been detected on the first two moons. Auroras also exist on other celestial bodies, but usually at wavelengths that the human eye cannot see.

Using the 10-meter-diameter Keck Optical-Infrared Telescope on Hawaii’s Mount Maunakea, scientists who made the relevant publication in the journal Planetary Science “Planetary Science Journal”led by his teacher California Institute of Technology (Caltech) Catherine de Kleer, reported that in all cases the aurora is caused by the strong giant magnetic field of the giant planet Jupiter.

The auroras on the four large moons are similar to those on Earth’s poles, but the gases on Jupiter’s moons are much thinner, resulting in a deep red aurora that shines nearly 12 times brighter than the green on Jupiter’s moons. our own planet.

On Io, columns of gases and dust of volcanic origin, enormous in size, reach a height of hundreds of kilometers, and because they contain various salts, they give the aurora there additional colors, in particular a yellowish-orange glow reminiscent of the night lighting in cities on Earth.

“The brightness of the different colors in an aurora tells us what the atmospheres of these moons are probably made of. “We found that molecular oxygen, like what we breathe here on Earth, is probably the key ingredient in the atmospheres of these icy moons,” said de Kleer. On the other hand, there is little evidence of water vapor, even though three large moons of Jupiter are estimated to contain oceans of liquid water beneath their thick icy surfaces.

As Jupiter’s magnetic field has a tilt, the auroras on its moons change in brightness as the planet rotates.