Monday, May 13, 2013

Farming on mars

Comments are closed on this old post, but gbaikie said something worth commenting on...
We don’t even have Mars sample return. It’s possible that it’s somehow toxic to plant life- though It doesn’t seem at all likely.
But it is toxic. 15% iron is toxic. The point is that it is in no way a show stopper. As a matter of fact, that iron is so useful we will need to process the soil for plants anyway when extracting it.

We don't need a sample return mission because we've got rovers sending us the data.

Nothing prevents us from farming on mars. We just need to get there.

Update: Going before congress. Via Rand.


Arizona CJ said...

I hate to sound a sour note, but... the notion of sending colonists on a one-way journey when we don't yet know if they can survive there is very worrying to me.

We'd need to build pressurized greenhouses, quite a lot of them, to support even a small outpost. That means a lot of mass to be landed on Mars. Most everything else they need would need to be likewise landed. That's a lot of upmass, and landing on Mars is far from easy.

ISRU solves some of this, and that's both an advantage and a risk. Can we make the soil safe for plants? Yes, we almost certainly can, but we are far less certain on how. Is iron the only issue? No. There are indications that salts are as well,to name just one. However, our knowledge is far from complete. I also suspect that, much like Earth, the soil has wide variances. Hydroponics might be a better choice, assuming that we have a viable water source (?).

Right now, we just don't know if plants can exist in Martian soil after we treat it in ways that we currently assume it needs. The Curiosity rover can do a great deal of analysis, and that helps, but it's limited in what it can look for, and also by geography; what applies in Gale Crater might be quite different in another location.

Sample return would be very expensive, so that's an issue too. Fortunately, there's a faster, cheaper way; in situ testing. Send up, as a small part of the next lander, a small glass capsule with some iron-fixing material inside. Add some Martian soil, a few seeds, and some water, and we'd have some results shortly, one way or the other. That's grossly simplified, but that's the gist of it.

ken_anthony said...

Mitigation requires sour notes. We do know they can survive. What we don't know is if we can supply them enough to overcome the dangers. So prudence means we over supply them.

We can fully supply a few dozen and should, but this should be considered backup. Primary will be farms for which they will need a known mass of UV and infrared reflecting plastic to hold about 10psi. We send more than they need. They need soil which will be a mixture of processed regolith and live soil brought from earth. They don't need that much live soil (but should bring more than they anticipate needing) since it will self produce more when mixed with the processed regolith.

Hydroponics lowers risk, but is also a backup. If they have to, they can break the regolith down to it's elemental components and mix it from there. This is just chemistry and we should include at least two chemists in the first landing. As you say, regolith will have different composition from place to place.

We just don't know if plants can exist in Martian soil

It won't be martian soil. We do know we can make soil. We do know that over time we will make it better. This is what humans with the right knowledge and experience do. They will have the entire earth for knowledge support.

What applies in Gale Crater might be quite different in another location

We can be absolutely certain it will be, at least in terms of concentrations. But whatever is there will have some concentration representative of the planet as a whole. The most common elements (the ones required for life) we already know are abundant and diverse. They just aren't going to land anywhere (I suggest near the equator over a known water source) where they will not find those elements.

In Situ testing is exactly what got Elon started. It really doesn't cost us anything to do it because we need to send supplies before colonists anyway. Your kind of sour notes are exactly what we need for mars mission planning. But we need to have the courage to go for it as well. We can do this. We should.

ken_anthony said...

We can fully supply a few dozen

I'm assuming 2.5mt per $190m Mars One Dragon lander.

A well chosen 2.5mt can supply dozens for years. Once we have colonists on mars we let NASA have the privilege of providing some of this. Again, over supply and diverse mitigation should be the plan.

ken_anthony said...

That means a lot of mass to be landed on Mars.

In most cases not that much. Each Zubrin 50m hobby farm should feed 3 to 4. So we send enough plastic for 8 farms minimum with the first dozen colonists. I need to look up some numbers to calculate the total mass for that, but it isn't all that much (and part of the reason for 10psi rather than 14.7psi.)

ken_anthony said...

BTW, we should consider ourselves lucky that the martian atmosphere is so thin. Mars is cold. A thin atmosphere doesn't draw away as much heat. That should allow us to keep the temperature in a greenhouse suitable for plant growth.

I suggest the farms be built above habitats. Keeping the habitats warm means the farm ground isn't a big heat sink problem either. We can engineer the problem, but should try to find natural solutions when we can.