Muon radiography for exploration of Mars geology

S Kedar,F H Webb,C E Jones,H K M Tanaka,C J Naudet,J P Plaut

doi:10.5194/gi-2-157-2013

Abstract

Abstract. Muon radiography is a technique that uses naturally occurring showers of muons (penetrating particles generated by cosmic rays) to image the interior of large-scale geological structures in much the same way as standard X-ray radiography is used to image the interior of smaller objects. Recent developments and application of the technique to terrestrial volcanoes have demonstrated that a low-power, passive muon detector can peer deep into geological structures up to several kilometers in size, and provide crisp density profile images of their interior at ten meter scale resolution. Preliminary estimates of muon production on Mars indicate that the near horizontal Martian muon flux, which could be used for muon radiography, is as strong or stronger than that on Earth, making the technique suitable for exploration of numerous high priority geological targets on Mars. The high spatial resolution of muon radiography also makes the technique particularly suited for the discovery and delineation of Martian caverns, the most likely planetary environment for biological activity. As a passive imaging technique, muon radiography uses the perpetually present background cosmic ray radiation as the energy source for probing the interior of structures from the surface of the planet. The passive nature of the measurements provides an opportunity for a low power and low data rate instrument for planetary exploration that could operate as a scientifically valuable primary or secondary instrument in a variety of settings, with minimal impact on the mission's other instruments and operation.

Highlights

Muon radiography was first applied for practical purposes as an imaging technique in the 1S95o0lsidby EE.aP.rGtheorge to measure the overburden over a tunnel in Australia (George, 1955), and in the 1960s by Luis Alvarez in his famous attempt to discover hidden chambers in the Second Pyramid of Chephren in Giza (Alvarez et al, 1970)
Muon radiography is a proven, simple, low cost, and efficient technology that could detect subsurface radiation-shielded habitable environments such as lava tubes or caverns that might not be detectable by any other technique available today
A mission that includes a muon detector could set the stage for a future mission to directly explore subsurface habitable environments on Mars

Summary

Introduction

Muon radiography was first applied for practical purposes as an imaging technique in the 1S95o0lsidby EE.aP.rGtheorge to measure the overburden over a tunnel in Australia (George, 1955), and in the 1960s by Luis Alvarez in his famous attempt to discover hidden chambers in the Second Pyramid of Chephren in Giza (Alvarez et al, 1970). The detected variations are of the order of a few percent in density contrast, making it a powerful tool for discriminating between hot rock and cold rock, rock and voids, and rock and water Applying this technique to Martian geology is attractive for several reasons: (1) cosmic rays are ubiquitous and generate secondary muons in any atmosphere; (2) a preliminary Monte Carlo simulation of the cosmic ray muon production on the Martian surface by Tanaka (2007) shows that the technique is ripe for application on planetary bodies other than the Earth; (3) high energy muons are extremely penetrating, passing through hundreds of meters of rock; (4) detectors, as collectors of muons radiation, are passive in the sense that they use nature’s cosmic rays and have significantly lower mass and power requirements than active imagers, such as radar, sonar or X-ray; (5) successful application of this technology on planetary bodies would bring new capabilities to future Solar System exploration missions by enabling highresolution imaging of the interior of planetary surface features with passive sensing of secondary cosmic ray muons, Published by Copernicus Publications on behalf of the European Geosciences Union

Figures158 igure 1

Figure 3

Candidate geological targets on Mars

Challenges for muon tomography on Mars

Findings

Summary