Cosmogenic 10Be as a Tracer for Recent Heliospheric Encounters with Interstellar Cold Clouds

TL;DR

This study models 10Be production to detect past interstellar cloud encounters with Earth, finding that only large clouds or high-energy particles produce detectable signals in geological records.

Contribution

It introduces a method to identify interstellar cloud encounters using 10Be measurements, highlighting the detectability limits based on cloud size and measurement resolution.

Findings

Detectable 10Be signals require parsec-scale clouds or high-energy particles.

Sub-parsec clouds are undetectable in crusts and sediments.

Ice cores with ≤10 kyr resolution can reveal sub-parsec cloud encounters.

Abstract

Recent works suggest there are periods when the Sun encountered massive interstellar cold clouds which compressed the heliosphere to within Earth's orbit. This would expose Earth to increased galactic cosmic rays (GCRs) and energetic particles of heliospheric origin (HEPs). We model 10Be production in Earth's atmosphere during possible interstellar cloud encounters and supernovae, and estimate their detectability in marine and ice records of variable temporal resolution. We find that encounters with sub-parsec-scale clouds cannot be detected via 10Be measurements in iron-manganese crusts. GCR signal is not detectable in ocean sediments; only parsec-scale clouds can be detected in iron-manganese crusts. Encounters with sub-parsec-scale clouds can be detected if Earth is exposed to HEPs, or by measuring ice cores with less than or equal to 10 kyr temporal resolution. We find that the peak observed by Koll et al. (2025) 10 Ma cannot be attributed to a supernova, but could be attributed to an interstellar cloud crossing.