Solar System planetary environments – in view of upcoming spacecraft explorations

This application is intended to provide funding for the continuation and growth of Lorenz Roth’s (LR) research and career as planetary space scientist at the KTH Space and Plasma Physics group.Three research projects (A, B, and C) are proposed for the first three years of this career grant. Projects A and B are a continuation of LR’s successful work on the Galilean moons of Jupiter.

Project C expands the recently funded work on the upper atmospheres of the ice giant planets.Project A deals with the crucial understanding of the mass loss from the volcanic moon Io.

Although Io is the confirmed main source of material of Jupiter’s magnetosphere, it is not understood if and how Io’s mass loss is time-variable.

We use two datasets of Hubble Space Telescope observations to (a) constrain the relation of the neutral atmosphere to the atomic escaping exosphere and plasma environment, and (b) measure the escape speeds of atoms.

In addition, we develop new targeted observing campaigns to map the variability in the molecular atmosphere and in the molecular escaping material.Project B focuses on two icy moons of Jupiter: Ganymede and Europa.

In preparation of the large JUICE mission, a fast-increasing number of theoretical and simulation studies on Ganymede is carried out in recent years, both on atmosphere and electrodynamic interaction.

We carry out a comprehensive analysis of the full set of HST images of Ganymede’s aurora producing a time-dependent 3D (= 4D) aurora model.

This 4D model uniquely enables the separation of spatial and temporal properties in the aurora and can serve as standard reference for validating the numerous simulation studies before the arrival of the spacecraft.

For Europa, the crucial existence of plume activity, with the potential to access subsurface habitable environments, remains unconfirmed.

We carry out a comparative study of all remote-sensing observing methods that were employed to constrain plume properties.

This provides reliable constraints on plumes and their characteristics thereby inform the planning for JUICE as well as NASAs Europa Clipper on this central topic.Project C builds on the recently granted project on Uranus’ hydrogen Lyman-α (Lyα) emissions and upper atmosphere.

Here we propose to obtain new HST data of Uranus to specifically address the question of seasonal variation in Uranus’ upper atmosphere suggested by infrared data. The new data complements existing data spanning an observing period of 34-years, i.e. time-scales of Uranus´ seasons. In addition, we analyze sets of images from Neptune and propose new targeted observations.

The datasets for both ice giants are interpreted in terms of their upper atmosphere density and temperature profiles (and similarities/differences) using radiative transfer modeling, providing key solar system references for studies of ice giant (Neptunian) exoplanets.The continuation and expansion of LR’s research will allow the long-term establishment of a working group at KTH with focus on the applicant’s research on planetary environments, before the arrival of the large ESA and NASA missions to the icy moons of Jupiter around year 2030.

The work on the ice giants will be a fundament in preparing and developing ideas for a first dedicated space mission to one of the (or both) ice giant planets of our Solar System.