Radiative Habitable Zones in Martian Polar Environments

Astrophysics, abstract
astro-ph/0507317

From: Mar\’ia-Paz Zorzano [view email]

Date: Wed, 13 Jul 2005 10:40:53 GMT   (888kb)

Authors:
C. Cordoba-Jabonero,
M.-P. Zorzano,
F. Selsis,
M. R. Patel,
C. S. Cockell

Comments: 44 pages, 8 figures

Report-no: CAB-lcasat/04057

Journal-ref: Icarus 175 (2005) 360-371

DOI: 10.1016/j.icarus.2004.12.009

The biologically damaging solar ultraviolet (UV) radiation (quantified by the
DNA-weighted dose) reaches the Martian surface in extremely high levels.
Searching for potentially habitable UV-protected environments on Mars, we
considered the polar ice caps that consist of a seasonally varying CO2 ice
cover and a permanent H2O ice layer. It was found that, though the CO2 ice is
insufficient by itself to screen the UV radiation, at 1 m depth within the
perennial H2O ice the DNA-weighted dose is reduced to terrestrial levels. This
depth depends strongly on the optical properties ofthe H2O ice layers (for
instance snow-lile layes). The Earth-like DNA-weighted dose and
Photosynthetically Active Radiation (PAR) requirements were used to define the
upper and lower limits of the nortern and southern polar radiative habitable
zone (RHZ) for which a temporal and spatial mapping was performed. Based on
these studies we conclude that phtosynthetic life might be possible within the
ice layers of the polar regions. The thickness varies along each Martian polar
spring and summer between 1.5 m and 2.4 m for H2= ice-like layers, and a few
centimeters for snow-like covers. These Martian Earth-like radiative habitable
environments may be primary targets for future Martian astrobiological
missions. Special attention should be paid to planetary protection, since the
polar RHZ may also be subject to terrestrial contamination by probes.

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