Naked Science Forum
General Science => Question of the Week => Topic started by: thedoc on 04/12/2016 13:46:30
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We find out if you can emulate a Martian environment in the kitchen, and if so, can you grow plants there? Plus we ask, are humans meant for monogamy?
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We answered this question on the show...
Chris - My name is Chris McKay. I'm a Planetary Scientist with NASA Ames Research Centre. I'm interested in Mars and particularly the question of life on Mars.
The question for today is, can plants grow on Mars and how could we simulate that here on Earth?
Well, I think there's two parts to that question.
The first part is, the soil on Mars. Could plants grow on that soil? Well, [img float=right]/forum/copies/RTEmagicC_011-mars-olympus-mons_02.jpg.jpg[/img]the best analogue we have on Earth for Mars soils is volcanic rocks – soils that have been produced from volcanic rocks. So, we could go to Iceland or Hawaii and collect some soils that have come from ground of volcanic rocks and use those as Mars analogues. And folks who have done that, it’s pretty easy experiment to do and try it. I think you'll find that most plants go fine in that kind of soil.
The other question though is about the environment of Mars. The temperature is very low, the atmosphere is very thin, and the atmosphere is carbon dioxide, very different from the Earth’s atmosphere. We can simulate those in the laboratory of course with a vacuum chamber and a big freezer.
We can get a sense of how to simulate those at home in your freezer. It’s cold, not as cold Mars, but almost as cold as Mars, and certainly, too cold for plants to grow. We can also simulate the low pressure by taking a small jar, putting water in it, boiling the water which will drive off the air, drive away the air, fill the atmosphere with water. We then seal that small jar and cool it. The water will condense creating pressures very much like the atmosphere of Mars. So, we can create low pressure environment, put in the freezer, now you have low pressure cold. We want to have CO2 in that as well. Instead of water, maybe we could try something like carbonated drink like Sprite. Then as it boils, it’ll put out water and CO2, drives away the air, we seal it, the water condenses creating a low pressure and there's a small amount of CO2 left.
Voila! A little bit of Mars in the freezer, low pressure cold!
Plants won't grow in that. We know that in order for plants to grow, it’s got to be a little thicker, a little warmer, maybe something in the refrigerator instead.
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I've wondered about that a bit.
There are some things that will be relatively easy to simulate.
Some things that would be difficult to simulate.
Keep in mind, like on Earth, the environment on the planet is not homogeneous, with cooler poles, and a warmer equator.
A few things that are different with Mars vs Earth:
- Gravity (about 0.376 g at equator)
- Atmospheric Pressure (0.0003 ATM to 0.011 ATM)
- Temperature, and diurnal temperature changes (min temp −143 °C, mean temp −63 °C, max temp 35 °C)
- Length of Year (just under 2 years)
- Length of Day (actually, that is pretty close, about 1 day, plus 37 minutes, I'd probably ignore that).
- Water, Minerals, Carbon
- Atmospheric Composition
- Atmospheric CO2
- Atmospheric Oxygen
- Sun (about half of the sunlight as on Earth)[/url]
The hardest thing to simulate on Earth would be low gravity, especially over an extended period of time. One can simulate higher gravity using a centrifuge. In Earth's orbit, one could get low gravity, then use a centrifuge to match the Martian gravity, 0.376g almost perfectly. However, one may also decide that this factor is not vital to the experiment, and far too expensive to simulate.
Atmospheric Pressure is a major issue for life, but relatively easy to deal with using a vacuum chamber. The martian atmosphere varies from 30 pascals (0.0044 psi, 0.0003 ATM) on Olympus Mons's peak, and 1,155 pascals (0.1675 psi, 0.011 ATM) in the depths of Hellas Planitia. If you are considering surface life, initially I'd target the maximum pressure.
The Armstrong Limit (http://en.wikipedia.org/wiki/Armstrong_limit) defines the pressure that water boils at body temperature (37°C, 98.6°F), or 0.0618 atmosphere or 6.3 kPa. This is 6 times the maximum surface pressure on Mars. All isn't lost. Your skin will still provide a generally good moisture barrier, although the Martian pressures would be extremely desiccating. Your mucous membranes, however, would boil away, and any cracks that would develop in the skin from the dryness would also boil away.
Microbes such as Amoebas, or even most bacteria would likely have problems with such a desiccating environment. Mature Trees have a thick bark, and the trunks may be able to withstand, or adapt to the low pressures. However, they depend on transpiration to pull moisture up from the roots and out the needles and leaves. It is quite possible that they would have extreme difficulty adapting to the Martian environment, especially since they also need to absorb carbon dioxide and release oxygen so you couldn't just paint over the leaves. Immature trees would likely be even worse off.
If I was looking for plants to try, I might look at water conserving desert plants such as cacti. The extreme night-time cold in the winter would be a problem, so perhaps look at some high altitude dryland plants, but still most Earth plants are optimized for a cold and a warm season, not warm days and bitter cold nights.
Perhaps you could consider the water problem as being part of the desiccating problem from the low pressure mentioned. There is likely some subsurface, and polar water, but getting and keeping it in liquid form at the equator may be problematic.
I'm not sure about the minerals. Perhaps a good comparison would be fresh volcanic ash and volcanic lava, which would be sterile, never having had life in it before. But, it may be a good source of minerals required by life.
The atmosphere is about 95% carbon dioxide, with most of the rest being Argon and Nitrogen, and less than 1% oxygen. This may actually be good. Consider that Earth's atmosphere is currently about 380 ppm, or about 0.00038:1 of the atmosphere. Thus, the partial pressure of carbon dioxide on Mars may actually be greater than on Earth. And, thus, if one could deal with the low pressure desiccation, the plants might be able to respire the Martian CO2 without supplementation.
Atmospheric oxygen, however, is low enough that aerobic microbes, and animals would be unable to survive. I assume oxides are common in the rocks, so one could potentially extract oxygen from rocks. But, still animals could not survive on such low oxygen.
I suggested that one may be able to create a dense atmosphere at the bottom of a very deep open trench on Mars. (http://www.thenakedscientists.com/forum/index.php?topic=46829.0), although it isn't without problems, not the least being difficulties making it, and without a cold-trap, it would still be water, and likely oxygen wasting.
Anyway, the best simulation of Mars would be built in a vacuum chamber, with "new" stone, or volcanic ash and lava for a substrate. Incorporate a freezer to simulate night, and an artificial sun. One could use natural sunlight with about a 50% shade. But, it may be easier to make artificial sunlight and heat.
Overall, however, one might plan to use surface greenhouses on mars.
Another thing to consider with life is that subsurface extremophiles may be able to be transferred to Mars without modification. Establishing life would be easiest a couple km below the surface, with liquid water, moderate temperatures, and pressures. That is, assuming that subsurface life isn't already there.
More data about Mars, and sources for some of the data in this discussion on the Wikipedia pages:
http://en.wikipedia.org/wiki/Mars
http://en.wikipedia.org/wiki/Atmosphere_of_Mars
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For some candidate organisms, maybe look at some of the creatures surviving in Antarctica?
Among multi-cellular organisms, look at the lichens (but not those that depend on bird poop for fertiliser).
http://en.wikipedia.org/wiki/Antarctic_microorganism#Mosses_.26_Lichens
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Antarctic Lichens?
Probably not a bad idea.
Another thing I thought about....
Reduced Nitrogen (Ammonia). Where is all of Mars' Nitrogen? Not in the sky? Even if there is enough CO2 in the air for photosynthesis, there may not be enough N2 in the air for current species of Earth organisms to make the ammonia they need to survive.
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There is likely to be some rather savage chemicals in Mars soil, like Perchlorate (ClO4). See http://en.wikipedia.org/wiki/Water_on_Mars#Phoenix
This gives the soil a rather basic pH of around 8.4, which might require some rather specialised extremophiles, see http://en.wikipedia.org/wiki/Martian_soil
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You might consider Halicephalobus mephisto, or the "Devil Worm" (http://en.wikipedia.org/wiki/Halicephalobus_mephisto), and the associated subterranean rock eating bacteria that it feeds on.
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We are at the moment conducting an experiment to see if plant species can germinate and then grow on both Mars soil and Moon soil. For this we use artificial soil, made in the US. It is possible to buy this and it is not very expensive. We only look at the soil, we assume that there will be an earth atmosphere. On Mars and the Moon this may be done in spheres. We will supply nutrient free water to water them, which probably will be present on the Moon and Mars. What is missing then is nitrogen, essential for growth, but we will also use species that can use nitrogen from the air.
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how about nitrogen? Plants need nitrogen. How much nitrogens are in Mars' soil???
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There is one thing that hasn't been mentioned. Even if Plants wouldn't Grow in Martian Soil (On Mars under it's particular Conditions), there Could be a Chance that Some Plants Could Grown in That same Soil under Earth's Own Conditions, even if not in (Controlled/Uncontrolled) Simulated Martian Conditions On Earth.