ATMOSPHERIC COMPOSITION OF GIANT PLANETS
Giant planets are mostly composed of Hydrogen, Helium and contain a small amount of methane and other trace species. The incoming UV sunlight initiates numerous photochemical reactions, leading to the formation of chemical radicals. These radicals combine into more complex molecules, ultimately increasing the chemical inventory in the giant planets.

In a series of paper, I have been studying Saturn's seasons, and how its pronounced obliquity affects the molecular distributions as a function of seasons and compared it to the observations from the IR spectrometer on Cassini (Cassini-CIRS).
I also studied how Saturn's seasonally varying atmospheric composition may affect its temperature field.

I have also worked on interpreting the Cassini observations performed during the Jupiter flyby in late December 2000. I have also studied how Jupiter's atmospheric dynamics and mixing processes affects its chemical composition.
Saturn's rings casting shadows on its atmosphere. Credit: NASA

NASA'S JUNO MISSION AT JUPITER

Picture
Credit: NASA/JPL
I am deeply involved in NASA's Juno mission. Juno was designed to study Jupiter from its interior all the way to its outer magnetosphere. Launched in 2011, Juno reached Jupiter on July, 4th 2016. Juno is placed on a polar and elliptical orbit. Every 53 days, Juno swoops by to get as close as 5000km above Jupiter's cloud top.

I am part of the magnetospheric working group, studying both Jupiter magnetospheric dynamics and aurorae. I am a member of the Ultraviolet Spectrograph (UVS) team led by Dr. Randy Gladstone. UVS was built at Southwest Research Institute. I am the calibration lead of UVS and am involved in the planning process and data pipeline.

SCIENCE WITH JUNO

Within the Juno mission, I study the interaction between the Galilean satellites and Jupiter's magnetodisk.  This interaction creates a perturbation at the galilean satellites that propagates along Jupiter's magnetic field lines. The main visible manifestation of that interaction are the satellite footprints, i.e., auroral spots that are magnetically connected to each of the satellites.

Juno allows characterizing the charged particule distributions that triggers the satellite footprints. This allows to better understand the nature of the electromagnetic perturbation that is the root cause of the satellite footprint auroral spots.
Scheme of the chain of processes leading to the Io footprint auroral spots. Credits: Bertrand Bonfond (ULg)
Artist's concept of the atmospheric collapse of Io, eclipsed for two hours each day (1.7 Earth days). Credits: SwRI/Andrew Blanchard
The interaction between Jupiter and Io
​
Jupiter's innermost moon Io shows a prominent volcanism due to the tidal effects of Jupiter, and the other galilean satellites. Io has a very tenuous atmosphere that gets enriched by frequent volcanic eruption.

Every Io's day (1.7 Earth days), it gets eclipsed behind Jupiter and it's surface temperature drops dramatically, causing its atmosphere to collapse.

With Juno, I study how Io's atmospheric collapse affects the electrodynamic interaction by monitoring the brigthness of the Io footprint auroral spots at Io move into eclipse behind Jupiter.

The main conclusion of this work is that the electrodynamic interaction at Io is not significantly affected by Io's atmospheric collapse in eclipse.
Discovery of a new type of aurora​

Jupiter's magnetosphere is incomparably larger than the Earth magnetosphere. It is about 5.3 million kilometers wide on average, the magnetosphere is 150 times wider than Jupiter itself and almost 15 times wider than the Sun, making it the larger structure in the Solar System.

The way the Jovian magnetosphere interact with the solar wind is still debated within the scientific community, and Juno as well as the Hubble Space Telescope bring crucial information to investigate this through the observation of auroral emissions.
​
In a recent paper, I led the discovery of a new type of aurora, characterized by mysterious concentric and expanding auroral emissions that Juno has seen on several occasions.

That emission is expanding rapidly over time, and its origin traces back to the interaction region between the Jovian magnetosphere and the solar wind. In that region, the shear of the flows between the solar wind plasma and the jovian plasma may generate instabilities, which propagate within the Jovian magnetosphere and ultimately trigger these auroral emissions.
Jupiter's magnetosphere (Credits: F. Bagenal & S. Bartlett)
Example of one of the newly discovered auroral feature
Figure showing where these newly discovered aurora were detected within Jupiter's auroral regions.