Aurorae is not only possible on Earth as it is also present on other planets and moons, such as the four of Jupiter's largest natural satellites. Even though astronomers became aware of the aurorae earlier, they were still in awe upon discovering some enticing flashes of light in wavelengths visible to the human eye.
The Jovian moons, namely Io, Europa, Ganymede, and Callisto are also called Galilean moons because of their size. Futurism reports that the aurorae were formed when sunlight reflected off the surfaces of the moons and swamped their modest glow.
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How Scientists Detected the Aurorae on the Jovian Moons
A team of astronomers led by Caltech and Boston University observed the moons in Jupiter's shadow using W. M. Keck Observatory's High-Resolution Echelle Spectrometer (HIRES) on Maunakea in Hawaii and also the Large Binocular Telescope and Apache Point Observatory.
Their observations allowed them to spot faint aurorae caused by the gas giant's strong magnetic field without competition from bright sunlight reflected off their surfaces.
In a pair of studies published in The Planetary Science Journal, astronomers performed a feat that is said to be tougher said than done after they managed to dodge the Sun by utilizing Jupiter's enormous shadow.
Katherine de Kleer, a planetary scientist at the California Institute of Technology and the lead author of both studies, said in a press release that these observations are tricky because of Jupiter's shadow that made the moons look nearly invisible. The light from their faint aurorae is the only confirmation they found in their telescope.
Yet the scientists were not just looking at the auroras for the sake of looking at them. They were also looking for water vapor in the atmosphere, and while there were plenty of auroras to dazzle the eyes, there was little sign of water vapor. It is a significant detail given that scientists are currently divided on whether several Galilean moons harbor oceans of water beneath their frozen surfaces.
Even if the presence of water is yet unknown, this latest research has offered a rare and interesting glimpse into the atmospheric components of these moons.
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Brighter than Earth's Aurora
These moons' aurorae are predominantly formed by energetic oxygen just like Earth's northern and southern lights. However, they are almost 15 times brighter and colored a deeper red due to the moons' smaller atmospheres.
According to CNet, these moons' atmospheres are thinner than Earth's that resulted in dancing lights that are redder than the greens compared to Earth's aurora borealis and aurora australis.
Moreover, volcanic gases and dust on Io contribute more sodium to the atmosphere, giving aurorae a yellow-orange hue. According to the experts, the ochre show might be up to 15 times brighter than what we observe on Earth.
As per de Kleer, the brightness of the different hues of aurora indicates what the atmospheres of these moons are likely constituted of They discovered that molecular oxygen, similar to what humans and animals breathe on Earth, is most likely the primary ingredient of the cold moon atmospheres.
Researchers noted in their press release that oxygen also triggers auroral lights in infrared wavelengths on Europa and Ganymede, which are redder than the human eye can physically perceive.
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