Mars Exchange
Food for Mars: Will Worms survive the Martian and Lunar soils?

Food for Mars: Will Worms survive the Martian and Lunar soils?

by Natasha Schön on Tuesday, 8th August 2017 in Food for Mars, People, Wieger Wamelink

One of the obvious key requirements for the use of worms on Mars and the moon will be their ability to survive in the ‘local’ regolith (soil). Not outside on the surface, swept by cosmic radiation, cold and without much of an atmosphere, but indoors in the safety of a dome. However, the regoliths may still pose threats, one of them being the sharp edges of the minerals. The first of our two pilot experiments was just about investigating if these sharp edged sand particles may harm the worms, because when the worms eat they swallow and mix together dead plant material with the soil (which is actually why they are so important to the process of creating healthy soils). 

Sharp-edged Sand
The moon sand in particular is very rough with sharp edges, the Mars sand less so. This is related to the origin of the sands. On the moon the soil, regolith, originates from the impact of (micro) meteorites and the slow but steady pulverizing effect of cosmic radiation. Since there is no liquid water or weather on the moon nothing happens with the sand, it just sits there, except when astronauts drive or walk on it. The sand is normally not moving which means that the sharp edges that form after pulverization will not be rounded as a result of weathering. On Mars this is happily less the case, although meteorites and cosmic radiation are also partly responsible for regolith forming on Mars. However, on Mars the planet-wide dust storms will cut off the sharp edges. And then there is Mars’s rather wet past with what are assumed to have been vast oceans and streams with water. They will have eroded the sand and have most likely deposited even clayish and loamy soils. The soil simulants we use don't only the same chemical composition, but also the same physical features as the real soils on Mars and the moon and therefore, also contain sharp edges. As a worm you are supposed to swallow this sand, lead it through your gut, mix it with organic matter and excrete it without being damaged by it.

The Worm Test
To test if the worms could survive the soil simulants and still do their job (chewing organic matter and mixing it with soil), we filled three glass pots with Mars and moon soil simulant and earth organic soil and added five worms per pot from my vegetable garden back home. Since this was only a pilot experiment, we only used one pot per soil. On top of the soil we added some food for the worms; dried plant material from the previous experiment. The pilot started in April and now, at the beginning of August, the worms are still crawling around happily in the soils. Sometimes we do not see them for days and then they suddenly pop up along the glass digging burrows in the soil. The worms show the same activity in all the three soils. When the soil dried out the worms did go into their rest stage, and watering the soils made them active again. So we are happy to report that no live animals were hurt during (the filming of this) experiment!

Story contributed by Wieger Wamelink, a Senior Ecologist at Alterra (Twitter: Wamelink_wieger).

More Information:

Sharp pyroxene shards in NWA 7034 (picture by Line Schug) indicated by the arrow.

Active worms in Mars soil simulant MSC 1A. Note the clay marbles used for drainage. In the next experiments we are going to use small rocks of the new MMS simulant for it. Here the worms are enjoying the potato peals.

Worms in the earth control potting soil, here also clay marbles for drainage and the potato peals for worm diner. Also visible old leafs of rye which are not all eaten yet.

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