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Comment by mapt | Hacker News Reader

So in a symbiotic bacteria/fungi/plant ecosystem, I can understand why CO2, H2O, and O2 might be able to remain in balance. But decomposition produces not only CO2, but CO, CH4, nitrate chemistry... I have trouble understanding why this cycle isn't at least a little bit leaky, since it seems like some of the trace gasses wouldn't automatically have all of the biological, solar, and marine sinks available in nature. I would be interested to know how the internal pressure of this experiment fluctuates due to phase transitions, especially chemical reactions which could potentially produce phase transitions that are not thermally or biologically reversible in the vicinity of STP.

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It really depends on the bacterial flora present in the container. Bacteria are incredibly diverse, and just as one decomposer may be a methanogen [1], a different species of bacteria present may be a methanotroph [2]. So given the right bacterial "mixture," a self-sustaining CH4 cycle is not unreasonable.

Additionally, CO is a metabolite for some methanogenic bacteria, specifically in production of acetyl CoA [3].

My point is, as long as enough diversity has survived in the ecosystem, it is quite possible that not only CO2/H20/O2 are able to maintain a balance, but _most_ common molecules would be able to remain at nontoxic levels for the plant.

[1]: http://en.wikipedia.org/wiki/Methanogen [2]: http://en.wikipedia.org/wiki/Methanotroph [3]: http://textbookofbacteriology.net/metabolism_7.html

It would also make sense that bacteria would tend towards stable equilibrium populations - ie a lack of a particular nutrient would result in a limited population in the species that require that nutrient.

By that logic if you had sufficient biodiversity to start there would be some limiting nutrient that would fix the stable state biomass of the whole system.

As long as there was a metabolic pathway to reach it, absolutely.

To me, metabolism is one of the most interesting biological topics. It is fascinating how intricate of a system has evolved and it shows how difficult it truly is to know the end consequences of changing literally any chemical concentration in the body.

Here is one of the more intricate maps for solely human metabolism: http://www.cc.gatech.edu/~turk/bio_sim/articles/metabolic_pa.... Crazy stuff.

In other words, the secret to having a viable sealed terrarium is in the compost. Get the right compost, with the right population of bacteria, and the whole thing will run forever.

I am interested in the idea of synthetic soils. Arriving on Mars and creating the right mix of sand, silt, and clay is easy enough. But it's the organic matter and biomass that makes soil what it is. Research on this might also have impacts on some parts of developing world where soil quity can be very poor. (Although that's often because anything that could go into the ground to improve soil has other uses).

One idea I've toyed with is building a "terrarium" (marsium?) with Mars imitation soil and atmosphere, and attempt to bootstrap some life in there.

I would imagine that some amount of adaptation will happen automatically. You have many kinds of bacteria in your compost, and the proportions will automatically adjust after the sealed ecosystem has been running for a while. Some strains might completely die off if they can't get the chemicals they need.

Project idea: start another one of these sealed gardens, but also include various sensors within the bottle/compartment (CO2, CH4, O2, temperature, humidity, pressure, whatnot; but also light levels.)

They can be pretty small and made to fit in nicely. The cheapest way to power them would probably be to use a simple coated electrical cable (through a layer of wax, or through something less leaky), I suppose.

Having them relay data in some fashion while having all the electronics not be exposed to erosion/etc might be a bit tricky.. ideally, just the actual sensor surfaces themselves would reside within; coated wires would all go through the seal, etc. Or, the devices could be (not very easily) shielded, and just the sensor surfaces be exposed..

Of course the most fun way to do this would be to have a whole self-sustaining arduino/whatever running inside, relaying data wirelessly, and having it be powered by small solar panels (would still need to take care of erosion/etc.)

Collect all data, plot it (including the light levels), and see if you can make anything out of it. :)

edit actually, I can now imagine a really large aquarium, with not much light passing into the very middle; for mostly entertainment purposes, it would be nice to also be able to place a cheapo camera there which could take (infrequent, like once every 5min or 20min) timelapses. Another camera with IR lens if needed, for neat composite images.. etc etc. Not sure of possible scientific value re: the latter, but hey!

I've had a terrarium in a sealed mason jar on my desk at work for 2 or 3 years now and have never once opened it. It seems like everything grows much much slower in there. There's some type of grass that has maybe grown 2 inches in that time and a leafy plant that hasn't grown appreciably either. The leaves don't really fall off, so decomposition is at a minimum. Perhaps the waste products of decomposition keep the bacteria and whatnot in balance.

It's almost certainly at least a bit leaky; glass carboys tend to let a surprising amount of gas get in around the bung, which never seals quite perfectly.

That said, even if it falls short of a 100% perfect hermetic seal it's still darn impressive.

Have you guys seen the SUPER SUPER LARGE sealed ecosystem. It's called earth. It's amazing how long it has lasted without any significant mass coming in or going out.

Other than several hundreds tons of cosmic dust per day according to http://www.universetoday.com/94392/getting-a-handle-on-how-m... .

Earth also loses helium and hydrogen. The current rate of loss is about three kilograms (3 kg) of hydrogen and 50 grams (50 g) of helium per second, according to Wikipedia. http://en.wikipedia.org/wiki/Atmospheric_escape

The reason it's difficult to understand is because this article is not true.

You don't happen to care to elaborate, do you?

I've looked all over the google and can't find anything that points to this being false.

The URL for one.

I believe they're complaining because it comes from "TheDailyMail". Sometimes people acquire biases towards certain news sources, and then completely ignore pieces from it regardless if it's reasonably true or not, simply by virtue of it coming from "TheDailyMail". Similar to how people grow biases towards Fox/VoA.

In fairness, the Mail has massive and well studied form in what we can generously call 'making shit up'.

Don't be silly. This kind of thing is not rare and exists in many schools throughout the country, just not many this old.

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