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Sounding the Ganymede’s crust with a GPR. V. Ciarletti 1 , A. Le Gall 1 , M. Biancheri -Astrier 2 , J-J. Berthelier 1 , S.M. Clifford 3 , D. Plettemeier 4 , M. Hamelin 1 1 LATMOS, Guyancourt, France 2 IDES, Orsay, France 3 LPI, Houston, TX, USA 4 TUD, Dresden , Germany .
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Sounding the Ganymede’s crust with a GPR V. Ciarletti1, A. Le Gall1, M. Biancheri-Astrier2, J-J. Berthelier1, S.M. Clifford3, D. Plettemeier4 , M. Hamelin1 1LATMOS, Guyancourt, France 2IDES, Orsay, France 3LPI, Houston, TX, USA 4TUD, Dresden, Germany International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
Scientific Objectives • Characterize the 3D compositional (ice purity) and physical (porosity, structure) properties of the Ganymede Landing Site down to a depth of ~100m to a few km • Identify potential shallow (<1 m depth) and deep (up to ~1+ km) structures • Clues to understand the large-scale geologic evolution of the Landing Site • Characterize the electromagnetic environment and potential activity of the thin atmosphere (ambient Jovian HF background noise, potential atmospheric discharges ) International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
Overview • A stationary, impulse, multiband HF GPRoperatedfrom the surface • designed to conduct geologic investigations of planetary environments in both the near and deep subsurface (~1m – few km) • An enhanced version of the low-frequency GPRs developed for • The original Mars NetLander (CNES) • The original ExoMars mission (mono and bi-static operations) International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
The instrument main features • Frequency bands • 2-4 MHz deep soundings (from 100 m to a few kms with a resolution of ~50m) • 3D mapping • 3 components of the magnetic field + 2 for the electrical field • Retrieval of the direction of arrival of the echoes - 3D mapping of the reflecting structures • Modes of operation • Active • Antenna impedance measurement • Passive • Detection of weak echoes • Deployment on the surface • Coherent additions up to 228 (in monostatic operation) to improve the SNR International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
Magnetic sensor Electrical antennas Mono-static configuration (NetLander) International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
Magnetic sensor Electrical antennas Mono & Bi-static configuration (former ExoMars mission) International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
Coherent additions efficiency International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
Electricalantennasdeployment system The antennas system • Electricalantennasdeployed on the surface (transmission and reception) • 2 perpendiculardipoles (2 X 35 m long resistivelyloadedribbon monopoles) International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
Magneticsensor The antennas system • Magneticantennas(reception) • 10 cm long searchcoilmagneticantenna International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
Demonstration of 3D investigation • Mono-Static Investigations of the Subsurface in Antarctic International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
Demonstration of 3D investigation • Mono-Static Investigations of the Subsurface in Antarctic Topography reconstruction International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
Application to Ganymede • In active mode: Assessing the stratigraphy of a grooved terrain, a crater or a putative cryo-volcanic features on Ganymede will significantly help to determine and describe the geological processes that have shaped the moon’s surface and bring new constraints on its age. International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
Application to Ganymede • In active mode: could contribute greatly to the understanding of the relationship between this subsurface ocean and the surface by revealing compositional boundaries between different ice sheets. International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
Measurement Simulation Simulation εr~3 σ~10-5 S/m ε r=3 σ =10 S/m - 5 Electrical HF antennaimpedancemeasurement Application to Ganymede • In the antenna impedance measurement mode: willhelp to characterizeGanymede’s crust composition and in particular the proportion of non-ice components in the near surface. International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
Application to Ganymede • Passive mode: will monitor Jupiter radiation and its variations with time. • Better to operate on the anti-Jupiter side of Ganymede! International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
Summary • The data acquired by such low-frequency GPR will provide local information about the geology of the Landing site: • at a scale (~100 m – a few kms) and resolution (~10 – 100 m) • including its composition, stratigraphy and structure. International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
Magnetic sensor Electrical antenna Mono-Static HF measurements Passive measurements Impedance measurements Mono & Bi-static configuration (former ExoMars mission) Bi-Static HF measurements International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
In profile: Tx 1st interface 2nd interface 3rd interface Demonstration of 3D investigation • Bi-Static Investigations of the Subsurface International Colloquium and Workshop “Ganymede Lander: scientific goals and experiments”
