Simplified, Earth's systems can be broken up into four "spheres" that constantly exchange matter and energy with one another:
- The atmosphere, which includes all gasses around the planet
- The hydrosphere, which includes all of the planet's water and related systems
- The geosphere, which includes the all the material within and below the crust
- The biosphere, which is comprised of every living thing on Earth
We have atmosphere, but why is it that the other 'spheres' do not have tags?
I suggest we make them, but some peer review would be nice.
"For questions about the gases which surround a planet or some other celestial body."
Current tag wiki. I think it's fine as-is.
"For questions about the liquids present on the surface of a planet and the associated systems."
Note that this is not synonymous with any other tag - in fact, very few tags cover this topic at all, yet multiple questions do (things like alien solvents and biochemistry, some weather patterns, erosion and landscape formation, chemical processes, and more). Examples include:
Can a water cycle exist on a planet without oceans?
Could water be extracted/harvested from clouds?
What's the quickest way to add oceans to a planet?
Could humans survive on a planet with only deuterium 'heavy water' made with hydrogen isotopes?
How rare is (clean, drinkable or useable) water in the solar system?
What would the conditions on a methane world look like?
An ammonia - not water - based alien race that breaths hydrogen
Could liquid silicon dioxide exist on the surface of Venus?
Eutectic Iron Life
Methanol/Ethanol (other alcohol) based life-form - aliens?
What conditions are necessary to support a vitriolic chlorine planet?
"For questions about the materials that compose a planet or other celestial body."
Related to geology and possibly synonymous; would be relevant to a plethora of existing questions that do not have the geology tag. Examples include:
What would the geology and climatology of an earth-like planet be if it's north pole is always facing it's star?
What geographic features occur at each type of tectonic plate boundary?
Can we breathe the moon's crust?
Alien exploration : drone digging earth crust
How much energy to destroy the crust of a planet?
How would the earth be different if the crust was at most 1km thick?
What happened when my scientist drilled a hole through Europa's “crust”?
What would perforating a continent do?
Will there be any effect on earth or an oceanic world if its crust and mantle lack radioactive elements?
Planet with dual core
Could We Restart Mars's Core With Antimatter?
Can an asteroid have a molten core?
Likelihood of a magnetosphere with a mercury core
What would happen at the core of a water world?
"For questions about the ecological dynamics of a whole planet or celestial body."
Broader than habitability; related to the seldom-used life; more specific than environment; more specific than biology. Examples include:
If we built a large moon close to Mars, could we make Mars a living world?
Ecocide with a clear deliberate intent
Could a hollow rocky planet the size of Jupiter be artificially created, and how would that affect species growing on its surface
Finding signs of life from afar
Would you shoot out DNA onto baby planets if you planned to visit it someday?
Could exoplanet with Earth's magnetic field orbiting a binary star system harbour intelligent life?
Can there be life on a planet with water, but without an atmosphere?
Nanobots Ecosystem, is it possible?
What if an Earth-like planet had no axial tilt? (impact on ecosystem)
Ecosystem of bladetree
How could you keep a rogue planet warm(ish)?
Would animals from Earth be able to survive and reproduce on this planet?
What would happen if there was no wind?
So what do you think? Are these tags relevant and/or reasonable? What changes would you make to them?