Plan 9: Detecting Atmospheric Deterrence Against Interstellar Monsters

TL;DR

This paper explores how exoplanet atmospheres might reveal signs of planetary defenses against hypothetical interstellar monsters, through specific chemical and aerosol signatures.

Contribution

It introduces potential atmospheric indicators of planetary deterrents, linking atmospheric chemistry and aerosols to defense mechanisms against extraterrestrial threats.

Findings

DMS/DMDS levels could produce observable mid-infrared features.

Silver hazes may cause optical brightening detectable in spectra.

Sea-salt aerosols could appear as muted spectral signatures.

Abstract

Exoplanet atmospheres are usually discussed as tracers of climate, chemistry, and habitability, but they may also preserve signatures of planetary defense. We consider three folklore-motivated deterrents against monsters: reduced organosulfur gases as anti-hematophage repellents, argentiferous reflective aerosols as anti-lycanthropic countermeasures, and haline aerosols as a counting problem for specters. We show that globally-mixed garlic-smelly levels of DMS/DMDS could produce observable mid-infrared transmission features, that silver hazes would show up as anomalous optical brightening, and that sea-salt lofting sustained by strong near-surface winds appears as muted spectra. None of these signatures is unique, which is precisely the observational challenge. A defended world may first appear merely sulfur-rich, bright, or hazy. Therefore, some atmospheres may encode not only biosignatures, but also evidence that the local biosphere has stopped being afraid of the dark.