4 ms·
Mars doesn't have hydrogen because at temperatures where water is liquid, the speed of hydrogen atoms due to temperature is greater than the escape velocity fro
by adekok 11y ago
Mars doesn't have hydrogen because at temperatures where water is liquid, the speed of hydrogen atoms due to temperature is greater than the escape velocity from Mars.
- mjklin 11y agoWouldn't they be held by surface tension?
- stephengillie 11y agoSurface tension is magnetic attraction between molecules. There's not enough negative magnetic attraction to hold them; they're repelled by all the other molecule nuclei.
- stephengillie 11y agoI thought it was just pressure - the more dense molecules push the Hydrogen out of the way as gravity pulls at them.
- adekok 11y agoPressure is the collective action of the molecules / atoms flying around and smashing into things. At "normal" temperature on Mars, hydrogen atoms have a thermal velocity [1]. That velocity is greater than the escape velocity from Mars. A lone hydrogen atom will typically bounce around a lot in the lower atmosphere. It eventually works it's way (via random scattering) to the upper layers of the atmosphere. Once the atom reaches the upper atmosphere... it's gone. It flies away, never to return. Keep that up for a billion years, and Mars loses most of the hydrogen it started off with. Oxygen is heaver, so it's thermal velocity is smaller than the escape velocity. [1] https://en.wikipedia.org/wiki/Thermal_velocity https://en.wikipedia.org/wiki/Thermal_velocity
- JoeAltmaier 11y agoSo the Mars atmosphere is a distillation column for gasses!
- lmm 11y agoEvery atmosphere is a distillation column for gasses. Oxygen and Nitrogen are similar enough that they don't separate (also Earth's atmosphere moves enough to mix), but you definitely find that e.g. Radon will sink to the floor, and lighter gasses like Helium will float up to high altitude.