The potential applications of muography to revealing sea shipwrecks

TL;DR

This paper evaluates the feasibility of underwater muon radiography (muon tomography) to reveal the contents of submerged shipwrecks and assess associated environmental hazards. A GEANT4-based Monte Carlo framework models muon transport through seawater, detector response, and the imaging pipeline, including a three-station muon telescope and detailed optical-photon simulation. Simulations of a trapezoidal wreck at 50 m depth filled with water, crude oil, or RDX show that a roughly seven-day exposure can produce 2D density maps and distinguish these fillings via muon transmission. The work highlights potential applications in environmental monitoring and marine archaeology while acknowledging limitations and avenues for improvement, such as accounting for environmental variability and enhancing detector resolution.

Abstract

Muon imaging, a non-invasive technique that utilizes naturally occurring cosmic muons, has emerged as a promising tool for exploring underwater objects, including shipwrecks. This study investigates the potential of muon radiography to examine the contents of wrecked ships in the Baltic Sea and other marine environments. These wrecks often pose significant environmental risks due to hazardous contents such as explosives and crude oil, making their detection and monitoring critical for environmental and safety considerations. Accurate modeling and imaging of such wrecks are therefore essential for assessing potential dangers and mitigating environmental impacts. To model the underwater muon flux in this study, an approach similar to that used in underground muon experiments was adopted. Cosmic muons were propagated through seawater using GEANT4, modeling their energy loss as they traverse water. The muons' kinematics and energy depositions were recorded during this process. The resulting distributions were tabulated and used as input for the primary particle generation module. This method enabled the generation of a realistic underwater muon flux at the desired depth above the shipwreck, allowing us to simulate various shipwreck filling scenarios. Assuming an exposure time of one week for a wreck located at 50 meters depth, our simulations demonstrate that muon imaging can sufficiently resolve density contrasts to distinguish between water, oil, and high-density materials. These results demonstrate the feasibility of muon radiography as a practical tool for underwater hazard assessment and shipwreck investigation.

Figures (7)

• Figure 1: (a) GEANT4 simulation of optical photon propagation in a single layer of stacked triangular bars is shown. (b) Two orthogonally oriented layers form a $1 \times 1~\mathrm{m}^2$ superlayer used for determining the $x$–$y$ coordinates of the muon hit position.
• Figure 2: (a) Cross-sectional view of the triangular scintillator bars illustrating the geometry used for hit position reconstruction. The red lines, separated by 2 mm, represent two incident muon trajectories simulated to evaluate the detector’s spatial resolution. (b) Distribution of reconstructed hit positions using asymmetry between upper and lower triangular scintillation bars for two simulated muon beams separated by 2 mm.
• Figure 3: The ROC curve for the distribution of reconstructed hit positions, obtained from the asymmetry between the upper and lower triangular scintillator bars for two muon trajectories separated by 2 mm.
• Figure 4: Illustration of the muon tracking principle in a telescope, from GEANT4 simulation. Muons with positive charge are shown in red and muons with negative charge in blue. A muon track is reconstructed when a spatial coincidence of hits is observed in all three tracking planes. Scintillation bars activated by the passing muon are highlighted in cyan.
• Figure 5: Schematic of muography imaging of an underwater shipwreck, modeled as a trapezoidal structure, with a muon detector placed on the seabed and oriented toward the shipwreck.