Ganymede is Jupiters largest moon and one of the most observed satellites in the solar system. The moon presents a natural laboratory for the study of many unique phenomena that may contribute towards the understanding of planetary systems similar to that of Jupiter and the habitability of such systems. Previous data on Ganymede has provided evidence of molecular oxygen and grooves on the surface. More recent data on the atmospheric composition of the moon asserts the presence of molecular water in the atmosphere as the result of sublimation from an underneath saltwater ocean. The data also reveals ongoing interaction between the water and the surface, which leads to the grooves and subsequent deposit of fossils. Taken as a bundle, the evidence points to the possibility of primitive life on Ganymede, and provides important strategic considerations for future missions to the Jovian system.

Introduction

Ganymede is one of the fifty-eight confirmed moons of Jupiter. It is the largest satellite in our solar system, and is even larger than the planet Mercury and Pluto, the dwarf planet. Interest in Ganymede has been fueled by the moons unique characteristics. In addition to being the only satellite body in the solar system to do so, it is also the only body in the outer solar system that produces its own magnetic field (Collins & Alexander, 2). This discovery was made by the Galileo spacecraft in 1996. Since then, other findings from have improved the prospect of life on Ganymede.

Methods

This experiment used archival data acquired by the Hubble Space Telescope Imaging Spectrograph from the year 1998 to 2010 as well as new spectra from the Hubble Cosmic Origins Spectrograph acquired in the year 2018. Two far-ultraviolet spectra taken by the Cosmic origins Spectrograph before and after Jupiter eclipsed Ganymede. A test was used to show that the oxygen atmosphere is too thin for the emission of 1304 A emission, which created the upper boundary for the abundance of O molecules. The spatial distribution of OI 1356 A and OI 1304 A emissions in images from the Hubble Imaging Spectrograph was analyzed. This method was justified by the reasoning that the impact of electrons produces substantially brighter 1304 A emissions when the atmosphere is comprised of O of H2O.

Results

Previous research had identified molecular oxygen in Ganymedes atmosphere, but had failed to identify expected molecular water, despite the relative intensity of oxygen emissions. These emissions were identified after the discovery of auroral emissions by the moon (Jenner). The interaction of Jovian magnetospheric plasma with this tenuous neutral atmosphere excites emissions from atomic oxygen, which produces stunning auroral emissions at Ganymede, (Collins and Alexander, 3).

Using new and archival data, this experiment found that an O2 + O + H2O atmosphere was consistent with the ratio of oxygen emission.It was also found that emission ratios changed proportionately to the radial distance from Ganymedes center, and that the intensity of the ratios requires the presence of H2O.

   

The results indicate strong evidence for the presence of water and material exchange between the oceans, icy surface and rocky floor. Howell and Pappalardo (4703) calculated their models using the finite difference code SiStER (Simple Strokes solver with Exotic Rheologies). They simulated the geological activity of Ganymede, with ice shell thickness remaining fixed in their simulations. The results indicated that the lithosphere advected from the side boundaries and would necessarily be replaced by asthenospheric ice. Additionally, the deformation occasioned within the lithosphere allowed the eventual exposure of ocean fossil material at the surface.

Discussion

The results indicate the presence of water underneath Ganymede. This ocean is located deep underneath the surface, about 100km to be precise. As shown in the calculations, patterns of sublimation of the pure ice under the surface affects the surface geology of Ganymede. This is the assumption proven by Howell and Pappalardo (4703). In their study, they proved that the bands on Ganymedes surface were formed through the process of sublimation from the underground, and went further to explain the variations in the lithosphere and their effects on the band formation. Effectively, the interaction between water, rock and heat creates a canvas for the masterpiece that is life. The evidence directly indicates that the conditions for life have been met, which increases Ganymedes interest in the eyes of astronomers. Additionally, Howell and Pappalardo (4703) show that the sublimation of ice leads to the surface deposits of ocean fossils. Consequently, anticipation for the upcoming JUICE (Jupiter Icy moons Explorer) mission by the European Space Agency is heightened, and justification is made for landing an instrument on the surface for further exploration. These discoveries continue to justify the exploration of the solar system in a bid to discover life and better understand the planet.

Works cited

Howell, Samuel M., and Robert T. Pappalardo. “Band formation and ocean-surface interaction on Europa and Ganymede.” Geophysical Research Letters 45.10 (2018): 4701-4709.

Jenner, Lynn. Hubble Finds First Evidence of Water Vapor at Jupiters Moon Ganymede. NASA, NASA, 21 Dec. 2021, https://www.nasa.gov/feature/goddard/2021/hubble-finds-first-evidence-of-water-vapor-at-jupiter-s-moon-ganymede

NASA Jet Propulsion Laboratory (JPL). NASAs Juno Spacecraft Hears Jupiters Moon. NASA Jet Propulsion Laboratory (JPL), 17 Dec. 2021, https://www.jpl.nasa.gov/news/nasas-juno-spacecraft-hears-jupiters-moon

Roth, Lorenz, et al. “A sublimated water atmosphere on Ganymede detected from Hubble Space Telescope observations.” Nature Astronomy 5.10 (2021): 1043-1051.

Acknowledgements

Great appreciation is given to given to Joachim Saur of the University of Cologne, whose assistance and ideas were instrumental to the development and execution of this project. I would also like to express my deepest gratitude to my friends in the astrology class who helped me in this project.