Soutenance de thèse de Pablo Rodriguez Ovalle le mercredi 4 décembre 2024

Titre de la thèse

"Study of Jupiter’s atmosphere with the first JWST observations"

Résumé

The polar regions of Jupiter are peculiar compared to the rest of the planet. This is largely due to the presence of charged particle precipitation in the auroral regions. This precipitation triggers a series of changes in the upper atmosphere. These include the warming of the stratosphere and thermosphere in and close to the auroral region, and the increase in the abundance of some hydrocarbons in the stratosphere, the result of ion-neutral related chemistry, adding new pathways for the production of these molecules. Some of these molecules extend their impact beyond the auroral region, since they may be related to the formation of hazes, which may extend up to 55◦N in the northern polar region, and up to 60◦S in the southern polar region. In this work, I have used the first JWST observations of Jupiter from the Early Release Science (ERS) 1373 program, to analyze the stratosphere of the south polar region of the planet. Specifically, I have used the MIRI/MRS instrument, a spectrograph operating in the mid-infrared. This study has involved an important part related to the processing of JWST observations. Since the observations analyzed were among the first JWST carried out, this work constitutes one of the first in terms of the processing of JWST data in solar system science. Given the high sensitivity of JWST and the high infrared radiance of Jupiter, some of the data showed saturation defects and wavelength shifts that varied across the detector image. I have developed desaturation and spectral correction techniques to obtain higher quality scientific products to work with. These tools have not only been applied to the MIRI/MRS instrument, but to others such as NIRCam or NIRSpec, and have been one of the great successes of the ERS 1373 program. From these observation I could analyze the three-dimensional thermal structure of the Jovian stratosphere (10 - 0.01 mbar) and the abundance of various molecules that inhabit this stratosphere (CH4, C2H2, C2H6, C6H6 ...). In addition, I have been able to find for the first time the spectral signatures of polar aerosols in the mid-infrared, just as Cassini/CIRS found them for Saturn and Titan. Thanks to the incredible sensitivity of JWST, I have been able to quantify its optical thickness and impact on the thermal structure of the planet. In addition, I have been able to analyze the remains of exogenous species, driven by the Shoemaker-Levy 9 impact back in 1994. I have analyzed HCN, as well as CO2 and H2O. It was the first time that we were able to observe the latitudinal distribution of H2O on Jupiter, and it was the first time since 2000 that we were able to see the latitudinal distribution of CO2 again. The simultaneous study of these two species has allowed us to establish possible relationships between them, probably due to the exotic chemical framework that occurs in the polar regions, due to the presence of the auroras.