Department Logo for Earth, Planetary, and Space Sciences

Planetary Science Seminar - winter-2016

Measuring the tidal Love number h2 of Europa and Ganymede

Jan. 7, 2016
noon - 12:50 p.m.
Slichter 3853

Presented By:

  • Gregor Steinbruegge - DLR
See Event on Google.
Subscribe to Calendar

Measuring the tidal Love number h2 of Europa and Ganymede

The potential habitability of the subsurface ocean of Europa and Ganymede makes the icy moons of Jupiter a lucrative target for planetary exploration. While NASA will investigate Europa with a flyby tour over a period of several years, ESA decided to investigate Ganymede with a dedicated orbiter. One of the top priorities of both missions is the characterization of the structure of the icy shell. It is a key measurement for future exploration and provides invaluable information on the thermal behavior and dynamics of the moons. However in order to e ffectively constrain the interior structure a combination of multiple measurements will be necessary. Numerous publications already pointed out the importance to measure both tidal Love numbers h2 and k2 (e.g. Wahr et al. (2006), Wu et al. (2001)) as well as potentially l2 (Hussmann et al., 2011) for constraining the ice thickness, which arises from the ambiguity between the rheology and the thickness of the outer ice layer (Moore and Schubert (2000),Wahr et al. (2006)). While the tidal Love number k2 describes the tidal secondary potential induced by the mass redistribution as a consequence of the external forcing by Jupiter, the tidal Love numbers h2 and l2 express the corresponding radial and horizontal amplitudes of the tidal deformation. k2 can be measured by radio science experiments but the measurement of h2 requires an altimeter. On ESA's Jupiter Icy Moons Explorer (JUICE) this task will be performed by the Ganymede Laser Altimeter (GALA). The only selected instrument onboard the Europa mission with altimetric capability is the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). While its main focus will be the direct detection of subsurface water reservoirs, we will show that it has the potential to also deliver altimetric measurements useful for the detection of solid body tides and therefore contribute a valuable contribution to the characterization of Europa's outer ice shell.

Transit timing variations of exoplanets

Jan. 14, 2016
noon - 12:50 p.m.
Slichter 3853

Presented By:

  • Katherine Deck - Caltech
See Event on Google.
Subscribe to Calendar

Transit timing variations of exoplanets

Probing the Interior Dynamics of Jupiter and Saturn with Gravity and Magnetic Fields

Jan. 21, 2016
noon - 12:50 p.m.
Slichter 3853

Presented By:

  • Hao Cao - Ca
See Event on Google.
Subscribe to Calendar

Probing the Interior Dynamics of Jupiter and Saturn with Gravity and Magnetic Fields

The inner working of solar system gas giant planets remain elusive after decades of exploration. One lasting debate concerns the nature of east-west zonal flows observed on the cloud level of these planets with amplitude on the order of 100 m/s: an observational fact is yet to be established about whether these flows are shallow atmospheric dynamics or surface expression of deep interior dynamics. There is a good chance that such an observational fact can be established, given the upcoming gravity and magnetic field measurements to be carried out by the Juno mission and the Cassini Grand Finale.

In this presentation, I will first describe a critical assessment of the applicability of the thermal wind equation (TWE) in calculating the gravity field associated with deep zonal flows. The TWE, which is a local diagnostic relation, captures the local density variations associated with the zonal flows while neglects the global shape change and density variations with non-local origins. Our analysis shows that the global corrections to the high degree gravity moments are small (less than a few tens of percent). Our analysis also shows that the applicability of the TWE in calculating the gravity moments does depend crucially on retaining the non- sphericity of the background density and gravity. Only when the background non- sphericity of the planet is taken into account, the thermal wind equation (TWE) makes accurate enough prediction (with a few tens of percent errors) for the high- degree gravity moments associated with deep zonal flows.

I will then turn to the magnetic signals associated with deep zonal flows. Using mean field dynamo theory (MFDT), we show that detectable magnetic signals are expected: in the spatial domain, poloidal magnetic fields spatially correlated with deep zonal flows are expected; in the temporal domain, periodic oscillations of the poloidal magnetic field are expected. The period of the magnetic oscillations is controlled by the amplitude of the shear in the zonal flow as well as the amplitude of the dynamo alpha-effect. Numerical magnetohydrodynamics (MHD) calculations designed to study the magnetic field zonal flow interactions seem to confirm the mean field theory picture for this problem.

Forced librations in longitude of Epimetheus, Enceladus, and Titan

Feb. 4, 2016
noon - 12:50 p.m.
Geology 4677

Presented By:

  • Bruce Bills - JPL
See Event on Google.
Subscribe to Calendar

Forced librations in longitude of Epimetheus, Enceladus, and Titan

TBD (Gravity of Enceladus and other bodies)

Feb. 11, 2016
noon - 12:50 p.m.
Slichter 3853

Presented By:

  • Luciano Iess - University of Rome
See Event on Google.
Subscribe to Calendar
Seminar Description coming soon.

Magmatic iron meteorites: pieces of asteroidal cores

Feb. 18, 2016
noon - 12:50 p.m.
Slichter 3853

Presented By:

  • Junko Isa - UCLA
See Event on Google.
Subscribe to Calendar

Magmatic iron meteorites: pieces of asteroidal cores

The geology of Titan with infrared and radar data

Feb. 25, 2016
noon - 12:50 p.m.
Slichter 3853

Presented By:

  • Anezina Solomonidou - JPL
See Event on Google.
Subscribe to Calendar

The geology of Titan with infrared and radar data

Titan's methane hydrologic cycle

March 3, 2016
noon - 12:50 p.m.
Slichter 3853

Presented By:

  • Juan Lora - UCLA
See Event on Google.
Subscribe to Calendar

Titan's methane hydrologic cycle

TBD (Ice remote sensing)

March 10, 2016
noon - 12:50 p.m.
Slichter 3853

Presented By:

  • Eric Rignot - UCI
See Event on Google.
Subscribe to Calendar
Seminar Description coming soon.