The Music of Cosmic Rays: Askaryan Effect as a Novel Planetary Geophysical Sensing Technique

Ultrahigh-energy cosmic rays continuously bombard planetary and small-body surfaces. When an ultrahigh-energy cosmic ray travels from space into a solid, particulate material, or atmosphere, it produces a relativistic cascade of secondary charged particles and an intense, coherent, wideband, linearly polarized electromagnetic pulse via the Askaryan Effect. This electromagnetic pulse is physically analogous to a sonic boom. Each electromagnetic pulse propagates through and is reflected and refracted by subsurface geophysical structures. Thus, cosmic rays serve as a pervasive, natural, non-destructive electromagnetic source for planetary geophysical sensing.

 

Here, we present an overview of a novel planetary remote sensing and in-situ measurement approach that leverages the electromagnetic ‘music’ made by cosmic rays via the Askaryan Effect and their detectable, interpretable radio signals. For the Moon, we present high-technology-readiness-level remote and in-situ instrumentation concepts that would detect and discover lunar ice deposits and geologic structures: The Cosmic Ray Lunar Sounder (CoRaLS) and the Askaryan Regolith Imaging Array (ARIA). We also present novel theoretical support for using the detection of signals generated by cosmic ray impacts and the Askaryan Effect to characterize near-subsurface structures on icy Ocean Worlds, such as Europa, including faults, subsurface lakes, and the depth of the icy regolith, and geophysical characterization of small bodies such as asteroids and comets.

 

This presentation is supported by the NASA Early Career Award in Planetary Science (80NSSC24K1214).