Background: Conceptual proposals to use nuclear detonations as a rapid means of terraforming Mars seldom quantify the radiological risks such events would impose on future surface settlements. Understanding fallout behaviour in the Martian environment is essential for evaluating the safety of prospective colonies. Materials and Methods: A Mars‑specific Monte Carlo fallout model was developed for a representative 100‑kt, fission‑dominated atmospheric detonation. The model simulates particle‑scale transport and deposition in a low‑pressure CO₂ atmosphere, estimates area‑averaged contamination (Bq m⁻²) over a circular colony footprint located downwind, and converts the resulting time‑dependent external dose into expected loss of life expectancy (life years lost). Multiple shielding configurations, including regolith, concrete, and lead were evaluated to quantify dose attenuation. Results and Discussion: For the selected source term, mean deposited activities over 1,000 days were approximately 10⁴ Bq m⁻² for Cs‑137 and Sr‑90, 10⁴–10⁵ Bq m⁻² for Ru‑106 and Ce‑144, and 10⁷ Bq m⁻² for Ba‑140. These contamination levels correspond to an unshielded life‑expectancy loss of roughly 0.1 years per colonist. Shielding reduced risk exponentially: meter‑scale regolith coverage or decimetre‑scale concrete walls were sufficient to lower life‑years‑lost to effectively negligible values. These findings indicate that while fallout from nuclear terraforming detonations could pose a substantial hazard to unprotected settlements, the shielding already envisioned for cosmic‑ray mitigation provides robust protection against such fallout. Conclusion: The study demonstrates that nuclear‑driven terraforming concepts must account for radiological fallout risks to surface habitats. Although unshielded colonies would face significant exposure, appropriately engineered settlements can reduce long‑term health impacts to minimal levels. Integrating fallout modelling into mission architecture and planetary‑engineering policy discussions is therefore essential for responsible planning of future Martian habitation.
Anjum Mavia (Thu,) studied this question.