New radio images collected by many telescopes on Earth are observing for the first time the direct impact of this volcanic activity on the thin atmosphere of the moon.
A study involving the data collected from these images was accepted for future publication in the Planetary Science Journal.
The images taken by ALMA, or the Aracama Large Millimeter / submillimeter Array of telescopes in Chile, provide a new perspective for the Moon and its distinctive color palette of yellow, white, orange and red. These colors are due to the sulfur gases spewing from the moon’s many volcanoes, which freeze when they meet the cold temperatures of the ice surface.
Although the idea of a moon covered with volcanoes suggests that Io will be a hot celestial body, Io̵
Io’s atmosphere is so weak that it is about a billion times thinner than Earth’s. Previous observations and studies of the moon have revealed that this atmosphere consists largely of sulfur dioxide gas.
“However, it is not known which process drives the dynamics in Io’s atmosphere,” said study author Imke de Pater, a professor of astronomy, terrestrial and planetary science at the University of California, Berkeley. “Is it volcanic activity, or a gas that has sublimated (changed from solid to gaseous) from the ice surface when Io is in sunlight?”
Researchers used ALMA to capture images of the moon as it moved in and out of Jupiter’s shadow to learn more about the moon’s atmosphere.
“When Io passes into the shadow of Jupiter and is out of direct sunlight, it is too cold for sulfur dioxide and condenses on the surface of Io. During this time we can only see volcanically produced sulfur dioxide. Therefore we can see exactly how much of the atmosphere is affected by volcanic activity, “said Lushch-Cook, a co-author and astrophysicist observer at Columbia University, in a statement.
The clarity of ALMA’s images reveals different jets of sulfur dioxide and sulfur monoxide coming from volcanoes, contributing between 30% and 50% of the moon’s atmosphere. Scientists have also seen potassium chloride gas, a common component of magma, come out of volcanoes. Researchers believe that this suggests that magma reservoirs differ between volcanoes.
Yo is only slightly larger than our moon, but it can’t be any different. Moreover, its environment is different from anything on Earth.
The moon, named after a mortal woman who turns into a cow during a battle between Zeus and Hera in Greek mythology, has lava fountains that can erupt to reach tens of miles in height.
Some of Io’s volcanoes are so powerful that their eruptions can be seen with the help of large telescopes on Earth.
The surface is also covered with lakes of molten silicate lava. With such a dramatic landscape, it would be an adventure to fly from Io, but you wouldn’t want to live there.
Io is caught between the huge gravity of Jupiter and the dragging of orbits from other moons on the planet such as Europe and Ganymede, which contributes to Io’s activity. Some of its volcanoes are massive, such as Loki Patera, which is 124 miles away.
The moon is in a decently locked orbit around Jupiter, which means that the same side of the moon is always facing the planet.
Hot volcanoes on a cold moon
Images from ALMA have revealed that Io’s atmosphere becomes incredibly unstable as it passes through the massive shadow of Jupiter. This happens every 42 hours during Io’s orbit around Jupiter.
During these “eclipses”, the sulfur dioxide of Io falls, which suggests that the lower atmosphere of the Moon mainly collapses and freezes on the surface. But when Io emerges from the shadow of Jupiter and receives sunlight, the gas returns.
“As soon as Io is exposed to sunlight, the temperature rises and you get all this (sulfur dioxide) ice subliming into gas, and you reform the atmosphere in about 10 minutes faster than what the models predicted,” de Pater said.
But researchers show that not all sulfur dioxide gases freeze during the temperature drop Io experiences while in the shadow of Jupiter. In fact, ALMA has been able to detect global sulfur dioxide radio emissions from what researchers call stealth volcanoes, which do not emit smoke or exposed particles but release gas into an atmosphere that is warm enough not to condense and freeze.
How do these hot processes develop under such a cold moon? The tug of Jupiter, Ganymede, and Europe heats the interior of Io, creating volcanoes that emit hot sulfur dioxide.
Eventually, the gas condenses and freezes in a thick layer of sulfur dioxide ice on the surface of Io. This layer is covered with volcanic dust, which creates the characteristic colors of Io.
“By studying the atmosphere and volcanic activity of Io, we learn more not only about the volcanoes themselves, but also about the tidal process and the interior of Io,” Lushch-Cook said.
Future observations and research will allow researchers to determine the temperature in Io’s lower atmosphere, which remains unknown.