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There's more to fertile soil than just rock dust,  water,  and ammonium nitrate (AN).  (BTW,  AN is a class 1.3 mono-propellant explosive,  even in fertilizer grade (a purity standard).  Adding fuel oil just increases the yield.  It is friction-sensitive,  shock-sensitive,  and can be induced to decompose (deflagrate) by heat;  which in large-enough piles,  can propagate into full detonation.  Try justifying the shipping of THAT in interplanetary supply.)  Any AN you use in agriculture on Mars needs to be locally produced.  We know there's perchlorate salts there;  there are probably nitrate salts as well.  These are all evaporites. 

You also need "organic matter",  which is primarily animal/human feces,  to mix with the rock dust,  which feces contains both carbon-hydrogen-oxygen-nitrogen compounds plus real,  live organisms (some microscopic,  some macroscopic-especially in the third world).  You don't have to ship the feces,  any people on Mars,  and any animals they bring,  will supply more than can be initially used.  Later on,  we'll see.  But in Asian rice culture,  it seems to balance out pretty well. 

Urine is another useful soil component,  although it might prove useful to remove some of the salt first.  The ammonia in it is fixed nitrogen,  the very thing plants need most.  Ammonia is actually better than AN in that respect,  or else the mass of AN fertilizer bags would exceed the mass of tanked ammonia at rural ag-supply places;  it does not. 

On Mars,  you are living in an environment that pressure-wise is very little different at 0.7% of an atmosphere from the vacuum of space.  It should be very easy to build a vacuum flash still rig that could separate the most of the water and nearly all of the ammonia from urine,  and so isolating the leftover brine as something to be disposed of by evaporation,  preferably not in contact with the soil.  Same thing might work in deep space travel.  Not a closed ecology,  but maximized recycling of what we can use. 

The "clean" all-hydroponic thing as most seem to conceive it may well prove to be a technological dead end.  Most of the useful plants we have are more symbiotic with the organisms in the feces than most folks want to admit.  We are not yet capable of engineering plants that do not need such symbiosis long-term. 

By the way,  although I most definitely do not claim to be an agricultural expert,  I have personally seen this process in action.  It is quite real.  I really do live on a cattle ranch in the midst of farm and ranch country.  My wife is a trained composter.  This is most definitely not theoretical knowledge from some school or some book.  It is the real McCoy. 

GW

but where do you find nutrients for the plant?

Wouldn't surprise me a bit to see mud polygons from an old lake bed.  The public news media are full of the story about the fossil gravel bar in the steam bed. 

There once was a time when Mars had a very much thicker atmosphere and warmer environment.  Streams and bodies of water,  all nice and "stable",  just like here.  The northern lowlands look an awful lot like an old ocean bottom,  too.

I would think that old stream beds and lake beds would be very good places to look with a real microscope for fossil remnants of microbial life.  Those odd traces in the Allan Hills meteorite might be a pretty good guide to the size and form of the things we would be looking for.  Too bad Curiosity isn't equipped for that. 

GW

wooooow!!!
geologists popping veins all over the world!

Luna 2019! Let's get back there before this decade is out!

louis wrote:

I've noted from NASA statements that the pics we see are enhanced to replicate earth light conditions.  Would be interesting to see what the "real" light conditions are. I imagine like a rather gloomy clouded day in the northern temperate zone on Earth.

They've actually been releasing both unaltered and white balanced images for everything, though I find it's sometimes tricky to track both down. The unaltered is closer to what a person would see on Mars, but the white balanced is more useful scientifically because geologists can use their intuition based on Earth coloration and better identify interesting targets.

For example, here's an unaltered image:
http://www.nasa.gov/images/content/6760 … l_full.jpg

And here's the white-balanced version:
http://www.nasa.gov/images/content/6760 … 3white.jpg

louis wrote:

RGClark wrote:

It's late southern Winter transitioning into early southern Spring on Mars.

  Bob Clark

Thanks Bob.  So we should see some higher temperatures in the coming weeks. Interesting.

Mars as a whole will also receive more light over the next several months at it gets closer to the Sun in its orbit. Its large eccentricity makes this a major seasonal effect, whereas it's negligible on Earth.

I have a question forn someone who knows computers: I am transitioning to a new computer. When I log into the New Mars Forums on the new computer, it pauses, redirects, and automatically logs me back out! Basically, it means I can read, but I can never post, because I can't get logged in. I'm writing this on my old computer, but I have to give it up in a few days. Any suggestions?

Louis:

http://www.360cities.net/image/curiosit … 8.19,110.0

The best is -still- yet to come