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Is it all the water on Earth or all the water on Earth's oceans? I'm pretty sure those aren't the same... I seem to remember reading that there's a very larg

Is it all the water on Earth or all the water on Earth's oceans? I'm pretty sure those aren't the same... I seem to remember reading that there's a very large amount of water chemically locked up in the Earth's crust.

zoklet-enjoyer 3y ago
I never thought about this before, but the volume of water in the atmosphere must be huge too, right?
- chmod775 3y ago
  Not really. Earth has hardly any atmosphere. The part with any density to speak of is just a thin film. To see for yourself, look closely at any picture of Earth and around around its circumference you will notice how little atmosphere there actually is[1]. It's something many people don't realize because from down here it looks like it goes up far. Just 16,000 meters up the atmosphere is unbreathably thin and most of Earth's oxygen lies below you. We have mountains that are higher than the main mass of Earth's atmosphere (50% is below 5.6km)[2]. The mass of Earth's hydrosphere is about 1.4 × 10^21 kg, while the mass of water in Earth's atmosphere is merely about 0.00002 × 10^21 kg[3]. [1] https://upload.wikimedia.org/wikipedia/commons/f/f6/Ocean_world_Earth.jpg https://upload.wikimedia.org/wikipedia/commons/f/f6/Ocean_wo... [2] https://en.wikipedia.org/wiki/Atmosphere_of_Earth https://en.wikipedia.org/wiki/Atmosphere_of_Earth [3] https://en.wikipedia.org/wiki/Hydrosphere https://en.wikipedia.org/wiki/Hydrosphere
  - bmitc 3y ago
    What rocky planets and moons have a thicker atmosphere? Or is common for rocky planets to have "thin" atmospheres?
    - shiroiushi 3y ago
      Venus has a much thicker atmosphere than Earth, about 92 times the pressure of Earth's at the surface. As for what's common, we don't have many examples of rocky planets (or moons) with atmospheres in our system to use as examples, and we can't see rocky exoplanets very well at this time, so who knows.
      - bmitc 3y ago
        Thicker, or denser? Or did you mean thick as in cake batter and not size? As far as I can tell, Earth's atmosphere seems to extend further into space than Venus'.
        chmod775 3y ago
        > As far as I can tell, Earth's atmosphere seems to extend further into space than Venus'. Depends on where you want to draw the line for "atmosphere". About 100km out is where the word "pressure" starts becoming near-meaningless on Earth, while on Venus you'd still have about three times as much to work with.
        shiroiushi 3y ago
        >As far as I can tell, Earth's atmosphere seems to extend further into space than Venus'. Technically, Earth's atmosphere extends infinitely far into space. It's not like there's some force-field holding it in; it just gets less and less dense with altitude. So the line depends on your definition, which must be some threshold. Anyway, Venus has about 90% of the gravity of Earth, so with 92x as much pressure at the surface (of a slightly smaller solid body), I think it stands to reason that at any given altitude, Venus's atmosphere has much higher density than Earth's. If Venus had far higher gravity, then this might not be the case at some altitude, but since its gravity is lower, then Earth's meager atmosphere should show slightly greater stratification I would think.
        bmitc 3y ago
        That doesn't follow. Planets are dynamical systems, not globs of material in situ. For example, Earth has a more substantial magnetosphere, which protects the atmosphere being blown completely away by the Sun.

zoklet-enjoyer 3y ago

I never thought about this before, but the volume of water in the atmosphere must be huge too, right?

chmod775 3y ago
Not really. Earth has hardly any atmosphere. The part with any density to speak of is just a thin film. To see for yourself, look closely at any picture of Earth and around around its circumference you will notice how little atmosphere there actually is[1]. It's something many people don't realize because from down here it looks like it goes up far. Just 16,000 meters up the atmosphere is unbreathably thin and most of Earth's oxygen lies below you. We have mountains that are higher than the main mass of Earth's atmosphere (50% is below 5.6km)[2]. The mass of Earth's hydrosphere is about 1.4 × 10^21 kg, while the mass of water in Earth's atmosphere is merely about 0.00002 × 10^21 kg[3]. [1] https://upload.wikimedia.org/wikipedia/commons/f/f6/Ocean_world_Earth.jpg https://upload.wikimedia.org/wikipedia/commons/f/f6/Ocean_wo... [2] https://en.wikipedia.org/wiki/Atmosphere_of_Earth https://en.wikipedia.org/wiki/Atmosphere_of_Earth [3] https://en.wikipedia.org/wiki/Hydrosphere https://en.wikipedia.org/wiki/Hydrosphere
- bmitc 3y ago
  What rocky planets and moons have a thicker atmosphere? Or is common for rocky planets to have "thin" atmospheres?
  - shiroiushi 3y ago
    Venus has a much thicker atmosphere than Earth, about 92 times the pressure of Earth's at the surface. As for what's common, we don't have many examples of rocky planets (or moons) with atmospheres in our system to use as examples, and we can't see rocky exoplanets very well at this time, so who knows.
    - bmitc 3y ago
      Thicker, or denser? Or did you mean thick as in cake batter and not size? As far as I can tell, Earth's atmosphere seems to extend further into space than Venus'.
      - chmod775 3y ago
        > As far as I can tell, Earth's atmosphere seems to extend further into space than Venus'. Depends on where you want to draw the line for "atmosphere". About 100km out is where the word "pressure" starts becoming near-meaningless on Earth, while on Venus you'd still have about three times as much to work with.
      - shiroiushi 3y ago
        >As far as I can tell, Earth's atmosphere seems to extend further into space than Venus'. Technically, Earth's atmosphere extends infinitely far into space. It's not like there's some force-field holding it in; it just gets less and less dense with altitude. So the line depends on your definition, which must be some threshold. Anyway, Venus has about 90% of the gravity of Earth, so with 92x as much pressure at the surface (of a slightly smaller solid body), I think it stands to reason that at any given altitude, Venus's atmosphere has much higher density than Earth's. If Venus had far higher gravity, then this might not be the case at some altitude, but since its gravity is lower, then Earth's meager atmosphere should show slightly greater stratification I would think.
        bmitc 3y ago
        That doesn't follow. Planets are dynamical systems, not globs of material in situ. For example, Earth has a more substantial magnetosphere, which protects the atmosphere being blown completely away by the Sun.