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Naomi Murdoch

Research

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 The InSight Mission

The InSight mission, selected under the NASA Discovery program for launch in 2018, will perform the first comprehensive surface-based geophysical investigation of Mars. The objectives of the InSight mission are to advance our understanding of the formation and evolution of terrestrial planets and to determine the current level of tectonic activity and meteorite impact flux on Mars. SEIS (Seismic Experiment for Internal Structures) is the critical instrument for delineating the deep interior structure of Mars, including the thickness and structure of the crust, the composition and structure of the mantle, and the size of the core. SEIS consists of two independent, 3-axis seismometers : an ultra-sensitive very broad band (VBB) oblique seismometer ; and a miniature, short-period (SP) seismometer that provides partial measurement redundancy and extends the high-frequency measurement capability.

I am involved in both the project team (noise model development, instrument testing, deployment preparation, …) and the science team of the InSight mission. My research interests include :

- Modelling the performance of the seismic instruments on Mars
- Interactions of the Martian atmosphere with the seismometers
- Attenuation of seismic waves in regolith


Top Left : The InSight Lander during integration. Top Right : Setting up performance tests of SEIS at CNES. Bottom Left : Simulations of the wind-induced mechanical noise on the seismometers. Bottom Right : Three images from a typical Spirit Navigation camera sequence showing a Martian dust devil

 Mars Microphone (Mars 2020 rover)

The SuperCam instrument suite onboard the Mars 2020 rover will include the Mars Microphone (provided by ISAE-SUPAERO) to support the Laser Induced Breakdown Spectroscopy (LIBS) investigation of soils and rocks on Mars. The primary purpose of the LIBS instrument is to investigate at remote distances the elemental composition of Martian rocks. The Mars Microphone will be used to investigate the hardness and other mechanical properties of the rocks that are otherwise unknown at remote distances.

Testing in Mars conditions is essential given the strong acoustic attenuation at high frequencies due to the low surface pressure. In order to test the Mars Microphone in a fully representative environment before flight, we use the Aarhus Wind Tunnel Simulator II (AWTSII) in Denmark.


Left : The Mars Microphone attached to the structural model of SuperCam. Right : Testing the Mars Microphone in the Aarhus Wind Tunnel.

 Asteroid Geophysics

Asteroids are covered by granular material that can range in size from a few microns (dust) or few hundreds of microns (sand) to a few centimeters or meters (gravels, pebbles, boulders). Despite the apparent simplicity of the geological history of small bodies, a large diversity of geological features has been observed in these low-gravity environments including impact craters, ponds of dust, slopes of varying gradients, smooth fine-grained regions and rough heterogeneous regions. There is strong evidence that asteroids are seismically active. Understanding the internal structure of an asteroid has important implications for interpreting its evolutionary history, for understanding its continuing geological evolution, and also for asteroid deflection and in-situ space resource utilisation. The dynamics of granular materials are also involved in the evolution of small bodies in our Solar System and understanding granular dynamics is critical for the design and/or operations of landers, sampling devices and rovers to be included in space missions.

My research interests include :

- Regolith dynamics in the low-gravity environment, including landing on asteroids
- Regolith formation
- Asteroid seismicity
- Developing techniques to probe the physical properties of asteroids


Top Left : Dust ponds on the asteroid Eros (Credit : JHU-APL,NASA). Bottom Left : An 18 km high mountain (twice the height of Everest !) on asteroid Vesta. Middle : Performing regolith dynamics experiments during a parabolic flight. Right : The novel facilty for reduced gravity testing developped at ISAE-SUPAERO

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