Case Study: Can Moss Grow in Martian Regolith Simulant?

Z. I. Sadeq <zacksadeq@att.net>

11 March 2016

Abstract

In-situ resource utilization (ISRU) is by far the cheapest way of supporting a future human colony on Mars. Research by teams in the Netherlands and elsewhere demonstrating the feasibility of growing a variety of plant species in Martian regolith simulant have shown encouraging results, albeit with limited success. Problems have included slow growth and low yield. Martian regolith characteristically lacks any organic matter and thus is naturally devoid of its essential by-product: bio-available nitrogen. Martian regolith also drains poorly, retaining moisture heavily. These problems could be remedied by the addition of dried moss to Martian regolith simulant as a soil amendment. Moss “slurry” can be used to sporulate Martian regolith simulant, and will germinate and thrive without the addition of anything but water. This is because moss, as well as other bryophytes, do not have true roots but instead create string-like rhizoids which serve only to anchor them to their substrates. Mosses do not absorb water or nutrients through their rhizoids, they do so atmospherically. Furthermore, interplanetary shipments of moss spores represents an exponentially more lightweight and cheaper alternative to shipping seed, embryonic plant material and other previously explored options to Mars.

Introduction

The question of how can agriculture support a future human colony on Mars is an emerging field of science. There have been numerous general proposals and conceptual frameworks regarding how to approach growing food and construction materials on location. One of the main problems researchers immediately noticed about Martian regolith simulant was the lack of bio-available nitrogen. Experiments conducted in the Netherlands demonstrated nevertheless green manure and food production are feasible. My goal was to find a simple, yet effective method of improving the quality of Martian regolith simulant. Moss cultivation has been used by humans for hundreds, if not thousands of years. The question was then drawn: can moss be grown in Martian regolith simulant? Initial research suggested it could be done and pointed to many advantages.

Materials and Methods

Regolith

Martian JSC-Mars-1A regolith simulant was purchased from a US-based NASA contractor. The regolith simulant was manufactured by NASA for the purpose of materials experiments and in-situ resource processing research. It has previously been shown to contain a surprising amount of plant-available nutrients and a relatively high soil pH of 7.3. The toxicity of the heavy metals contained within plants grown in the regolith is as of yet undetermined [1].

Containers

The substrate was placed for use inside of clear and “food-safe” container, 250 ml as moss prefers as much light and moisture as possible. Four holes less than 0.5 mm were placed in the lid to allow for some free exchange of air. 66 grams of regolith simulant was placed in the container. Relative humidity within the container was found to be between 81-99% at all times. External conditions of the grow room were checked on a 24-hour basis and kept between 66-73 F degrees, 55-75% relative humidity.

Lighting

Samples were placed in containers directly under a single, 13 watt fluorescent lighting tube producing 900 lumen @ 6500K at a distance of 15 cm.

Moss

Wild moss was collected directly from the outdoors in the southeastern United States, a humid subtropical climate, in early winter. Red clay is prevalent in the area and moss is commonly found thriving on it. Samples were collected from clay found with a soil pH of approximately pH 8.5. Samples were then gently pureed with distilled water (pH 5.5, ppm 0007) and afterwards the solution poured on top of the Martian regolith. There ended up being at least three distinct species of moss. Two were identified as Thuidium delicataulum and Dicranum scoparium.

Results

The experiment was started on the evening of January 11^th, 2016. Fledgling growth was observed within 18 days. The first and only watering (pH 5.5, ppm 0012) occurred on day 14. Watering beyond this point was determined to have been in excess and was therefore stopped. Samples were thriving by day 23. On day 36, the tallest length of moss was measured at 8 cm. Some die-back of old growth was also observed at this point. The experiment was terminated on day 60. From the original 30.24 g of Martian regolith simulant, the experiment yielded 47.36 g of moss. As of June 7^th, 2016, the samples are still alive and well, with multiple layers of dead growth and new moss now formed on top.

Conclusion

Given that the experiment was restricted by the use of simulant and environmental conditions, it is at least highly feasible that moss could be cultivated indoors on a prospective Martian colony for use as a soil amendment. It can be said to thrive in JSC-Mars-1A regolith simulant. Among some of the appealing benefits are its low maintenance qualities. The sample was never fed any nutrient solution and only watered a single time. Total amount of energy used over a 60-day period was only 18.72 kWh.

Further experimentation must be carried out determine the feasibility of cultivating moss on Mars itself, in and around fluvial plains, mimicking the temperature, moisture and low-gravity of the Martian frontier. Experiments are also needed to determine the efficacy of regolith-grown moss as a nitrifying and pH-reducing soil amendment.

The container also became contaminated with a few different species of wild cloves and alfalfa.

References

1. Can Plants Grow on Mars and the Moon: A Growth Experiment on Mars and Moon Soil Simulants. Wieger Wamelink, Frissel, et al. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0103138