Enabling Martian habitability with silica aerogel via the solid-state greenhouse effect

Abstract

The low temperatures1,2 and high ultraviolet radiation levels3 at the surface of Mars today currently preclude the survival of life anywhere except perhaps in limited subsurface niches4. Several ideas for making the Martian surface more habitable have been put forward5,6,7,8, but they all involve massive environmental modification that will be well beyond human capability for the foreseeable future9. Here, we present a new approach to this problem. We show that widespread regions of the surface of Mars could be made habitable to photosynthetic life in the future via a solid-state analogue to Earth’s atmospheric greenhouse effect. Specifically, we demonstrate via experiments and modelling that under Martian environmental conditions, a 2–3 cm-thick layer of silica aerogel will simultaneously transmit sufficient visible light for photosynthesis, block hazardous ultraviolet radiation and raise temperatures underneath it permanently to above the melting point of water, without the need for any internal heat source. Placing silica aerogel shields over sufficiently ice-rich regions of the Martian surface could therefore allow photosynthetic life to survive there with minimal subsequent intervention. This regional approach to making Mars habitable is much more achievable than global atmospheric modification. In addition, it can be developed systematically, starting from minimal resources, and can be further tested in extreme environments on Earth today.

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Fig. 1: Schematic of the solid-state greenhouse habitability concept for Mars.
Fig. 2: Image of silica aerogel used in the experiment.
Fig. 3: Results of the silica aerogel solid-state greenhouse warming experiments.
Fig. 4: Attenuation of UV radiation by silica aerogel.
Fig. 5: Simulated warming underneath a silica-aerogel solid-state greenhouse habitat on Mars.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

Code availability

The one-dimensional solid-state greenhouse numerical model is available open source at https://github.com/wordsworthgroup/Mars_SSG_2019.

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Author information

All authors discussed the experimental and numerical results and contributed to a draft version of the manuscript. R.W. proposed the solid-state greenhouse habitability idea, performed the experiments and wrote much of the manuscript. L.K. helped to write the sections on site selection on Mars and silica aerogel properties, and compiled data on the evidence for subsurface water sources. C.C. provided input on the nutrient, UV and pressure constraints on Martian habitability and on the ethical considerations.

Correspondence to R. Wordsworth.

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The authors declare no competing interests.

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Peer review information: Nature Astronomy thanks Joshua Bandfield, Dirk Schulze-Makuch and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Tables 1–2, Supplementary Figs. 1–5.

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