3 ms·

This may be a stupid question, but can anything be planted in Martian soil, even if the atmosphere was corrected? I always assumed not.

gpm 6y ago
Other than the perchlorate problem (which is a real problem, but they can be baked out with heat as I understand it) I don't think we know any reason why not. You'd have to fertilize the soil of course, but fundamentally plants don't need that much to grow. A lot of hydroponics use a completely inert "gravel" like substance and just wash a nutrient solution through on occasion.
- eqvinox 6y ago
  Do you know if there's any knowledge on how much fertilization you'd need to bring in? Or: whether it actually makes sense to use Martian soil to grow things on? If it doesn't supply much, one might just stick to hydroponics...
  - Ididntdothis 6y ago
    I can’t imagine Mars soil having any usable nutrients since there are no microbes or any other biological activity. You probably have to bring or produce all fertilization from scratch.
    - serf 6y ago
      Mars soil has a ton of required nutrients for vegetation. [0]. It might not all be in amounts easily scavenged, but they're mostly there. [0]: https://www.nasa.gov/feature/can-plants-grow-with-mars-soil https://www.nasa.gov/feature/can-plants-grow-with-mars-soil
lordofgibbons 6y ago
Based on everything I've read it should be possible. One would just need to add organic material and cultivate the symbiotic microbes, and plants should have no problem.
AnotherGoodName 6y ago
On the atmosphere point that's one thing that isn't as much of a problem. Plants can breath in Mars atmosphere and pressure. Sure the pressure is 0.6% comparing Mars/Earth but the CO2% is 0.04% when comparing Earth/Mars. In other words the partial pressure of CO2 on Mars is actually higher than on Earth. Which is great for CO2 breathing plants. If the temperature was raised a plant would have more CO2 available even with the much lower pressure than on Earth. Indeed experiments with 95% CO2 (matching Mars) and 6millibars pressure (matching Mars) and with martian soil showed that Potato's grow fine. https://cipotato.org/blog/indicators-show-potatoes-can-grow-mars/ https://cipotato.org/blog/indicators-show-potatoes-can-grow-... The only adjustment was temperature!
- wollstonecraft 6y ago
  But how is this possible? Water has a vapor pressure of 23 millibars at 20 C, meaning water would boil from the leaves.
  - AnotherGoodName 6y ago
    It boils but it takes many hours to boil off completely. Here's a study of the time taken to evaporate water in a near vacuum at 20C: https://www.hou.usra.edu/meetings/lpsc2014/pdf/2060.pdf https://www.hou.usra.edu/meetings/lpsc2014/pdf/2060.pdf 25ml of liquid water takes 3 hours to completely boil off under vacuum. Less if the water is mixed in with other substances (eg. soil). The inner structure of the plant itself is capable of trapping water to an even greater extent. To the point where water directly boiling off the plant directly isn't significant. Note that this was simulating asteroid conditions. Mars is slightly better at retaining water since it has slightly more pressure. This is why it's pretty likely that we're seeing flowing water on Mars each summer: https://www.nasa.gov/press-release/nasa-confirms-evidence-that-liquid-water-flows-on-today-s-mars https://www.nasa.gov/press-release/nasa-confirms-evidence-th...

gpm 6y ago

Other than the perchlorate problem (which is a real problem, but they can be baked out with heat as I understand it) I don't think we know any reason why not. You'd have to fertilize the soil of course, but fundamentally plants don't need that much to grow. A lot of hydroponics use a completely inert "gravel" like substance and just wash a nutrient solution through on occasion.

eqvinox 6y ago
Do you know if there's any knowledge on how much fertilization you'd need to bring in? Or: whether it actually makes sense to use Martian soil to grow things on? If it doesn't supply much, one might just stick to hydroponics...
- Ididntdothis 6y ago
  I can’t imagine Mars soil having any usable nutrients since there are no microbes or any other biological activity. You probably have to bring or produce all fertilization from scratch.
  - serf 6y ago
    Mars soil has a ton of required nutrients for vegetation. [0]. It might not all be in amounts easily scavenged, but they're mostly there. [0]: https://www.nasa.gov/feature/can-plants-grow-with-mars-soil https://www.nasa.gov/feature/can-plants-grow-with-mars-soil

lordofgibbons 6y ago

Based on everything I've read it should be possible. One would just need to add organic material and cultivate the symbiotic microbes, and plants should have no problem.

AnotherGoodName 6y ago

On the atmosphere point that's one thing that isn't as much of a problem. Plants can breath in Mars atmosphere and pressure. Sure the pressure is 0.6% comparing Mars/Earth but the CO2% is 0.04% when comparing Earth/Mars. In other words the partial pressure of CO2 on Mars is actually higher than on Earth. Which is great for CO2 breathing plants. If the temperature was raised a plant would have more CO2 available even with the much lower pressure than on Earth. Indeed experiments with 95% CO2 (matching Mars) and 6millibars pressure (matching Mars) and with martian soil showed that Potato's grow fine. https://cipotato.org/blog/indicators-show-potatoes-can-grow-mars/ https://cipotato.org/blog/indicators-show-potatoes-can-grow-... The only adjustment was temperature!

wollstonecraft 6y ago
But how is this possible? Water has a vapor pressure of 23 millibars at 20 C, meaning water would boil from the leaves.
- AnotherGoodName 6y ago
  It boils but it takes many hours to boil off completely. Here's a study of the time taken to evaporate water in a near vacuum at 20C: https://www.hou.usra.edu/meetings/lpsc2014/pdf/2060.pdf https://www.hou.usra.edu/meetings/lpsc2014/pdf/2060.pdf 25ml of liquid water takes 3 hours to completely boil off under vacuum. Less if the water is mixed in with other substances (eg. soil). The inner structure of the plant itself is capable of trapping water to an even greater extent. To the point where water directly boiling off the plant directly isn't significant. Note that this was simulating asteroid conditions. Mars is slightly better at retaining water since it has slightly more pressure. This is why it's pretty likely that we're seeing flowing water on Mars each summer: https://www.nasa.gov/press-release/nasa-confirms-evidence-that-liquid-water-flows-on-today-s-mars https://www.nasa.gov/press-release/nasa-confirms-evidence-th...