1:45 PM - 3:15 PM
[O11-P60] A Study of Atmospheric Composition and its Change on Galileo Satellite by Spectroscopic Observations
Keywords:Galilean satellites, Optical Spectrum
This study is an investigation of the atmospheric composition of the Galilean satellites Io, Europa, Ganymede, and Callisto, with the goal of observing changes in the atmospheric composition of these satellites over time.
Using the school's 35cm telescope and spectrograph, visible light spectra were taken four times on 1/27, 3/14, 3/21, and 3/2 for Io, four times on 1/23, 1/30, 3/21, and 3/28 for Europa, once on 3/14 for Ganymede, and once on 1/23 for Callisto. The spectrum of Jupiter was also taken at each observation for comparison. The spectra were processed using Subaru's image analysis software Makali`i, and spectra were created using Makali`i's graphing function. Atmospheric elements were identified from the wavelengths of absorption lines in the spectra. The abundance of an element is estimated by the area of the triangle corresponding to the width and depth of the element-specific absorption lines in the Excel spectrum. The area of the satellite (e)/area of Jupiter (m) was then calculated. If this value is greater than 1, the component is considered to be contained in the satellite.
As a result, we determined that magnesium (hereafter Mg) and hydrogen are present on Io and Europa. Especially in H-alpha,H-beta, H-gamma, and H-delta, relatively large changes in the e/m values of absorption lines were observed depending on the observation date. In Io, the e/m of Mg remained 1.3 times higher than that of H-alpha. However, the area changed slightly; as the area of Jupiter increased, the area of Io also increased. At Ganymede, e/m values of 2.1 for sodium, 2 for iron, 1.3 for calcium ions (3933 angstrom), 1.7 for calcium ions (3968 angstrom), and 2.8 for H-delta were determined to be present in the atmosphere.
This led us to consider that there might be some relationship between the area of Mg on Jupiter and the area of Mg on Io. Therefore, we created a scatter plot with the area of Mg of Jupiter on the horizontal axis and the area of Mg of Io on the vertical axis. The result looked like a linear function with a strong positive correlation with a determination constant of 0.97. The same operation was performed for Europa, and a similar result was obtained with a determination constant of 0.86. Furthermore, the slope of this linear function is smaller for Europa, corresponding to the fact that the effect of Jupiter's light decreases as one moves away from Jupiter. The y-intercept of this linear function can be rephrased as when the area of Jupiter is 0, i.e., when there is no influence of Jupiter, so we can say that it is the area of the absorption line at Io alone for that component. However, when this work was performed for Io's hydrogen, no correlation was found, with determination constants of 0.38 for H-alpha, 0.18 for H-beta, 0.10 for H-gamma, and 0.16 for H-delta, respectively. The y-intercept of the linear function that appears represents the area of the absorption line in Io only. As mentioned above, the area of the absorption line of hydrogen changes in Io, which is thought to be the reason why the y-intercept differs from observation to observation and does not become a linear function. We focused on the increase or decrease of H-delta, which is the most UV-extended absorption line of hydrogen in the visible light region, and considered that the amount of energy given to io changed for some reason. We considered that a possible cause might be a change in the tidal force of Europa, which orbits outside of Io, and checked the position of the Galileo satellite on the observation date using mitaka, a simulation software developed mainly by the National Astronomical Observatory of Japan (NAOJ). The results showed that on 1/27, when H-delta was highest, Io was close to the situation where it was sandwiched between Jupiter and Europa. A similar phenomenon was also observed for sodium. Since sodium is a component of Io's volcanic gases, hydrogen is also thought to be generated from the volcano. This could be interpreted as hydrogen being generated by some chemical reaction between hydrogen sulfide and water, but since there is no scientific evidence, this is a subject for future research.
Using the school's 35cm telescope and spectrograph, visible light spectra were taken four times on 1/27, 3/14, 3/21, and 3/2 for Io, four times on 1/23, 1/30, 3/21, and 3/28 for Europa, once on 3/14 for Ganymede, and once on 1/23 for Callisto. The spectrum of Jupiter was also taken at each observation for comparison. The spectra were processed using Subaru's image analysis software Makali`i, and spectra were created using Makali`i's graphing function. Atmospheric elements were identified from the wavelengths of absorption lines in the spectra. The abundance of an element is estimated by the area of the triangle corresponding to the width and depth of the element-specific absorption lines in the Excel spectrum. The area of the satellite (e)/area of Jupiter (m) was then calculated. If this value is greater than 1, the component is considered to be contained in the satellite.
As a result, we determined that magnesium (hereafter Mg) and hydrogen are present on Io and Europa. Especially in H-alpha,H-beta, H-gamma, and H-delta, relatively large changes in the e/m values of absorption lines were observed depending on the observation date. In Io, the e/m of Mg remained 1.3 times higher than that of H-alpha. However, the area changed slightly; as the area of Jupiter increased, the area of Io also increased. At Ganymede, e/m values of 2.1 for sodium, 2 for iron, 1.3 for calcium ions (3933 angstrom), 1.7 for calcium ions (3968 angstrom), and 2.8 for H-delta were determined to be present in the atmosphere.
This led us to consider that there might be some relationship between the area of Mg on Jupiter and the area of Mg on Io. Therefore, we created a scatter plot with the area of Mg of Jupiter on the horizontal axis and the area of Mg of Io on the vertical axis. The result looked like a linear function with a strong positive correlation with a determination constant of 0.97. The same operation was performed for Europa, and a similar result was obtained with a determination constant of 0.86. Furthermore, the slope of this linear function is smaller for Europa, corresponding to the fact that the effect of Jupiter's light decreases as one moves away from Jupiter. The y-intercept of this linear function can be rephrased as when the area of Jupiter is 0, i.e., when there is no influence of Jupiter, so we can say that it is the area of the absorption line at Io alone for that component. However, when this work was performed for Io's hydrogen, no correlation was found, with determination constants of 0.38 for H-alpha, 0.18 for H-beta, 0.10 for H-gamma, and 0.16 for H-delta, respectively. The y-intercept of the linear function that appears represents the area of the absorption line in Io only. As mentioned above, the area of the absorption line of hydrogen changes in Io, which is thought to be the reason why the y-intercept differs from observation to observation and does not become a linear function. We focused on the increase or decrease of H-delta, which is the most UV-extended absorption line of hydrogen in the visible light region, and considered that the amount of energy given to io changed for some reason. We considered that a possible cause might be a change in the tidal force of Europa, which orbits outside of Io, and checked the position of the Galileo satellite on the observation date using mitaka, a simulation software developed mainly by the National Astronomical Observatory of Japan (NAOJ). The results showed that on 1/27, when H-delta was highest, Io was close to the situation where it was sandwiched between Jupiter and Europa. A similar phenomenon was also observed for sodium. Since sodium is a component of Io's volcanic gases, hydrogen is also thought to be generated from the volcano. This could be interpreted as hydrogen being generated by some chemical reaction between hydrogen sulfide and water, but since there is no scientific evidence, this is a subject for future research.