admin We now have evidence that water vapour exists in the atmosphere of Ganymede, the biggest moon in the solar system, which orbits Jupiter. The frozen water on Ganymede’s surface may have sublimated, without melting, from a solid to a gas.
Ganymede’s surface is comprised of both dark, cratered regions and brilliant, grooved regions, which create fascinating patterns. Experts have long believed that Ganymede holds a great deal of water, perhaps even more than Earth. Yet, because Ganymede is so far from the Sun, liquid water can only exist beneath a thick coating of ice.
It is believed that Ganymede has three primary layers: an iron core, a rocky mantle, and a layer of liquid and frozen water. Below the massive ice layer (about 500 miles/800 kilometers) there may be liquid water. There is water no matter what, and where there is water, there may be life.
Researchers have discovered surface water that is not frozen for the very first time.
As part of a broader program of observations, Lorenz Roth of the KTH Royal University of Technology in Stockholm, Sweden, was using Hubble to quantify the amount of oxygen on Ganymede. Roth and his team utilized data from two telescopes: Hubble’s Cosmic Origins Spectrograph from 2018 and Space Telescope Imaging Spectrograph photos from 1998 to 2010 (STIS).
In 1998, the Space Telescope Imaging Spectrograph (STIS) of the Hubble Space Telescope captured the first ultraviolet (UV) images of Ganymede. These images demonstrated that the moon’s atmosphere was emitting light in a particular manner. Auroral bands are visible on the moon. These are comparable to the aurora ovals visible on Earth and other planets with magnetic fields. This is an example of evidence that Ganymede possesses a permanent magnetic field. Because of the existence of molecular oxygen, the ultraviolet findings were comparable (O2). At the time, it was believed that the discrepancies were due to atomic oxygen (O), which emits a signal that alters one UV hue more than the other. NASA, ESA, and Lorenz Roth are credited (KTH)
At least, this was the original interpretation of UV evidence indicating the presence of atomic oxygen from 1998. Yet, Roth’s team was astonished to discover virtually no atomic oxygen in Ganymede’s atmosphere. Thus, there must be another explanation for why these UV aurora photographs appear distinct.
When the scientists examined the UV images of the colored bands of charged gas known as auroral bands more closely, they discovered additional evidence that Ganymede’s surface temperature fluctuates significantly throughout the day. At noon, the equatorial regions of Ganymede may become enough warm for the ice surface to release (or “sublimate”) a few water molecules.
This is consistent with what we have learned from Hubble. Roth discovered what he initially believed to be oxygen at the equator but now believes to be water vapor.
Roth explained that only molecular oxygen had hitherto been recognized. “This is the result of charged particles eroding the surface of ice. Now-measured water vapor originates from ice sublimation, which is generated by the thermal escape of water vapor from heated icy locations.
Given the European Space Agency’s planned mission, this revelation makes Ganymede a far more interesting site. The Jupiter ICy moons Explorer (JUICE) probe is scheduled to launch in 2022 and settle on Jupiter in 2029. The mission will devote three years to a comprehensive examination of Jupiter and its largest moons, including Ganymede.
Roth noted, “Our results can offer the JUICE instrument teams with significant information that can be used to optimize their observation plans and spacecraft utilization.”
Increasingly, astronomers view Jupiter and Saturn’s icy moons as potential birthplaces for life. It was once believed that they were inhospitable, frozen wasteland, but the more we examine them, the more likely it seems that humanity may inhabit there. Even while Ganymede could possess life, it does not necessarily do so. That is something that will require further investigation.
