We have learned about Io in great details in our two previous articles on this volcanic moon of Jupiter. However, there is something that we did not learn in as much details as we should have. That’s none other than the collapsing atmosphere of Io. Yes, you read it right. The atmosphere of Io collapses and then re-emerges and this happens on a regular basis. So, here are the questions that we are going to answer in this article:
- What causes collapsing atmosphere of Io?
- How frequently does this happen?
- Which research showed collapsing atmosphere of Io?
Let us begin…
What causes collapsing atmosphere of Io?
We know from our article on Io’s atmosphere that the atmosphere of this ‘Most Volcanically Active Body in Our Solar System’ is mainly composed of sulfur dioxide. However, the distance of Io is really far from our Sun. So, it is pretty cold out there.
The moon becomes even colder when it enters into the shadow of Jupiter. In other words when Jupiter gets in between our Sun and Io, Io becomes colder that what it already is. The temperature becomes so cold that the sulfur dioxide that makes up the atmosphere actually freezes and turns into frost, which falls on the surface of the moon.
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When the moon re-emerges from the shadow of the mother planet and gets in line of direct sunlight, the temperature rises and sublimation of sulfur dioxide takes place. This means that the frozen sulfur dioxide frost is heated up by the sun rays, converting it directly into gas from ice.
So, when the sulfur dioxide in the atmosphere freezes and falls on ground, the atmosphere actually collapses. When in direct sunlight, the frozen sulfur dioxide turns into gas and brings the atmosphere back. This means that the atmosphere is more like a collapsible gate. It just collapses at one point and the re-emerges at another point in time.
What is the frequency of collapsing atmosphere of Io?
Wondering just how frequently the atmosphere of Io collapses and re-emerges? This happens every single Ioian day! Researchers have found that Io stays in the state of collapsed atmosphere just for 2 hours of Ioian day. Note that Io orbits Jupiter in approximately 1.77 Earth days but it stays in the shadow of Jupiter for just 2 hours. So, after two hours when Io reappears out of the shadow of Jupiter, the atmosphere reappears.
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Which research showed collapsing atmosphere of Io?
The study was done by Southwest Research Institute located in Colorado. One of the researchers in the team that studied the collapsing nature of Ioian atmosphere is known as John Spencer. It is Spencer who said about Io’s collapsing atmosphere. In order to study Io closely, the team of researchers used the following:
- TEXES or Texas Echelon Cross Echelle Spectrograph.
- Hawaii’s Gemini North Telescope.
Using these two instruments, the researchers managed to see Io not only slide into the shadow of Jupiter but also watched the moon emerge out of the shadow and enter into direct sunlight. Previously, all the observations of the atmosphere of Io took place when the moon was in the shadow of Jupiter. This prevented researchers from observing the collapsing atmosphere of Io.
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In the study the researchers found that when the moon enters into the shadow of the Jupiter, its surface temperature plummets to a whopping -270°F but when it emerges out of the shadow of Jupiter, it attains the temperature of -235°F. When in shadow, the sulfur dioxide turns into frost and falls on surface of Io. In sunlight, the surface warms up and the frozen sulfur dioxide sublimes and gets converted into gas.
When sulfur dioxide freezes, the atmosphere of Io collapses but when it sublimes, it pumps up the atmosphere.
Researchers say that though volcanoes on Io are responsible for releasing massive amounts of sulfur dioxide in atmosphere of Io, the atmospheric pressure actually gets controlled by the Sun on a day-to-day basis. Also, sunlight is directly responsible for controlling ice temperature of Ioian surface.
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