As I wrote at the beginning, if you put living organisms in a sealed container and close the lid, it becomes a Mini-Earth.
There is no doubt about this.
However, it is worth discussing the definition of Mini-Earth again for the following two reasons.
One is to clarify the relationship with similar concepts, and the other is that the large-scale Mini-Earth experiments that have actually been carried out are far removed from the explanation above.
Therefore, I will add a little more explanation.
First, there are similar concepts such as the "Balanced Aquarium" and the "Lorenz Aquarium".
The "Balanced Aquarium" is an aquarium that is established without using any equipment such as heaters, air pumps, or lights.
The word "balanced" probably means that the oxygen cycle, carbon cycle, and nitrogen cycle are all functioning properly.
The lack of temperature control means that it is best to use animals caught locally.
The "Lorenz Aquarium" is probably the origin of the "Balanced Aquarium", and is mentioned by the animal behaviorist Konrad Lorenz in his book "Solomon's Ring".
My explanation is not a direct copy of that book, but I think the meaning is the same.
The difference from Dr. Lorenz's time is that in modern times, when starting an aquarium, it is common to have a filter or air pump, lights if you put in aquatic plants, carbon dioxide injection, and a heater if you put in tropical fish, and it is also common to have a huge initial investment and optional equipment such as soil, bacteria, and filtration materials.
Nowadays, Lorenz aquariums are a very small minority.
However, what is a small artificial pond, commonly referred to in Japan as a biotope may be close to Lorenz aquariums in both ideology and practice.
As mentioned above, modern aquariums are dominated by a variety of equipment and methods that require a huge amount of effort.
If we focus on the effort rather than the equipment, the most typical examples are "feeding" and "water changes."
It may not be enough to be called a counter to this trend of the times, but there are people in the world who think, "Let's try to find ways to avoid using equipment and to make things as effortless as possible."
If there are many aquatic plants growing in a large aquarium, small shrimps will survive and have a new generation even if you stop feeding them.
Small fish that can survive by eating the shrimp little by little can also be raised without feeding.
However, naturally, the number of shrimps and fish is much smaller than the number that can be raised by feeding them normally.
Also, the water in the aquarium decreases due to evaporation, so, even if you give up changing the water, you need to supply water by "adding water."
If you focus on only efficiency extremely, you will choose a method of confining the ecosystem in a container, sealing it in, even forbidding feeding and adding water, and forbidding any interaction with the outside world other than light and heat.
This is called a "Perfect Aquarium," and the freshwater Mini-Earth given as an example in this blog can be said to be a typical example of a "Perfect Aquarium."
However, on the other hand, it is a bit doubtful whether the Perfect Aquarium is the representative of Mini-Earth.
The origin of the term "Mini-Earth" is still unknown, but in fact, it has a history of being researched with the aim of applying it to space development.
In other words, it was expected to be applied to future migration to the moon or Mars, or, on a more realistic level, to food and waste recycling in manned Mars probes.
The most famous example is the Biosphere Project, which created a huge facility in the Arizona desert and tried to confine humans and make them self-sufficient for two years.
Recently, a smaller but slightly smarter experiment was conducted at a facility in Rokkasho Village, Aomori Prefecture.
Considering this history, we can see that "Mini-Earth" and "Perfect Aquarium" are completely different concepts.
These "Mini-Earths" are not "aquariums" at all, and are not "Lorentz-like" at all.
For example, it is too inefficient to leave the disposal of waste to living organisms.
In addition, the mass of materials that can be carried on board a manned Mars probe is extremely limited in an environment like that of a manned Mars probe.
So, there may be some leeway in terms of energy if solar power generation or nuclear batteries are used.
For this reason, if humans were to be crammed into a spaceship to create a "Mini-Earth," it would be more realistic to use electrical equipment to treat waste.
Even if it were not a spaceship, waste is decomposed by microorganisms in real-life sewage treatment on Earth, but this is a large-scale industrial process, and large-scale aeration and separation from sludge are carried out using electricity.
To sum up, the only condition for a "Mini-Earth" is to block substances, and there is no problem using the equipment enclosed inside.
In addition, "aquaponics," in which edible shrimp and freshwater fish are raised in aquariums and the nitric acid that accumulates in the aquariums is used to grow edible plants such as tomatoes, may be more realistic in terms of its applicability to space development.
If the astronauts' mechanically sanitized excrement were used as food for the fish, it would be an excellent form of material circulation.
The rest is a matter of personal preference, but if you were that astronaut, would you be able to eat the tomatoes that were produced in this way?
Even if you could eat tomatoes, would you be able to eat the fish and shrimp in the aquarium?
Surprisingly, these traits may be the qualifications required for astronauts to explore Mars.
Next Article
Previous Article
