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Modeling Volcanic Plumes on Jupiter’s Moon Io

  • A giant plume (red) erupts from Io's equator over the course of an Io day. As surface frost warms, a sublimation atmosphere (blue) is produced. Plume material becomes suspended in the sublimation atmosphere and spreads over a huge area. Eventually the surface cools and the atmosphere and plume material sticks to the surface.
  • The simulated deposition ring of the Pele plume, with a Galileo image of Pele on Io's surface inset. The simulation captures the ovoid shape and the angle of the major axis, as well as the sharper north end and north/south gas jets in the interior. Fans of low density to the east and west compare well with the black fans seen in observations, and in simulations of Pele which include dust the particles are seen to fall in these areas.
  • Galileo image of the lava lake at the center of the Pele plume, which I take as the source of the plume for my simulations.
  • Ground-level number density contours for gas emerging from a half-annular vent. Streamlines converge on the focal point along the symmetry plane, and a jet of gas shoots out to the right.
  • A simulated Pele plume. Gas and dust rises from the vent region (the blue box in the middle). The gas falls back on itself under gravity, and when falling gas meets rising gas an umbrella-shaped canopy shock is formed, and the canopy gas falls to the ground in a large ring. Dust decouples from the gas before the canopy, is spread out by the canopy shock, and falls to the ground much closer to the plume source.
  • Side-view of a plume emerging from a half-annular vent seen along the symmetry plane. A large region of high gas density forms above the focal point where the gas shocks and turns.
  • An SO2 plume at Io's north pole being bombarded by Jupiter's plasma torus. Plasma inflates and heats plume canopies asymmetrically.
  • A comparison of Pele's deposition ring with and without plasma bombardment. Plasma causes the canopy to inflate and the ring to become thicker, more uniform, and more diffuse. Adding plasma produces better agreement with the observed ring (Galileo spacecraft observation on right).
  • A giant plume at 30 degrees north latitude in Io's sublimation atmosphere at noon. The plume suppresses net sublimation where its canopy intersects the atmosphere, and plume material spreads out over the top of the atmosphere in a huge area around the plume source.

Io is the most volcanically active body in the solar system, and its volcanic plumes rise hundreds of kilometers above the surface.  They rise far above the atmosphere, and I model this plume expansion into a near-vacuum with Direct Simulation Monte Carlo.  I simulate Pele, one of the largest plumes, in 3D using observations of the caldera to guide my choice of source geometry.  My goal is to explain the physics behind the deposition pattern and plume structure seen in observations. I also simulate plumes alongside other features of Io’s environment, like its sublimation atmosphere and Jupiter’s plasma torus, to understand how plumes fit into the big picture.