Elastic wave analyzer for icy sub-surfaces (EWAIS) in the solar system

We propose to develop and demonstrate a breadboard of an Elastic Wave Analyzer for Icy Sub-surfaces (EWAIS) instrument suitable for ocean worlds. The EWAIS will provide data for answers to fundamental science questions about the sub-surface structure of water-bearing worlds (e.g., Europa, Enceladus, and Titan) and structure of icy regions on Mars, including critical information about their origin and evolution. These bodies have been identified as high-priority targets of the NRC Planetary Science Decadal Survey, which noted a lack of technology readiness as one impediment to related missions. EWAIS generates and receives elastic waves using array of piezoelectric transducers capable of operating at temperatures as low as 30K. The breadboard will use reflected signals from discontinuities in the materials' impedance (the product of wave velocity and density) along the wave path. Analysis of the acquired data will determine the elastic properties, presence of cracks, cavities and other discontinuities, as well as the thickness of ice and liquid layers. The EWAIS will be developed with a novel dual-frequency transmitters array that will enable reaching distance of kilometers thru ice. This transmitter array will be the first planetary instrument of this kind. It will be driven by piezoelectric transducers with a bouncing constrained mass that impacts a thumper. The mechanism itself has been conceived and implemented as the actuator of the ultrasonic-sonic drilling system developed by members of the proposal team under the PI's leadership. The task development objective is to produce a breadboard that weighs <5 kg, packaged into 0.3 m diameter by 0.2 m height, that uses <5 Watts average power to emit >200 dB. The primary EWAIS drive frequency will be transmitted in the range of 20 to 40 kHz and the secondary converted low frequency (LF) is in the range of 0.1 to 1.0 kHz. These dual frequencies correspond to two depth ranges that can be analyzed, with resolutions of tens of centimeters in the region of tens to hundreds of meters and tens of meters on the kilometers scale, respectively. Owing to the nature of elastic waves, the waves transmitted by the proposed instrument are not impeded by conducting media such as saline water/ice. Therefore, the EWAIS is applicable to regions in planetary icy bodies that are inaccessible via electromagnetic based Ground Penetrating Radar (GPR), which is currently the mainstay for characterizing the sub-surfaces of planetary bodies. The proposed EWAIS will allow characterizing the sub-surface of any planetary icy body in the solar system, including Enceladus, which can be as cold as 34K. The analyzer will be applicable for operation from any in-situ platform including surface assets (e.g., lander and rover) and sub-surface assets (e.g., melting probes). The developed breadboard and analytical algorithms will be demonstrated using a 90K ice testbed containing layered structure and simulated discontinuities. The proposed task will advance the TRL from 2 to 4. More »