I do not know about all worlds or all alien races and their water or oxygen needs.

I do know that some others have water and oxygen and some do not.

Not all liquid is H2O.

Mars has H2O with a much higher mineral content.

Many worlds have liquid oceans, streams, rivers, ponds and lakes, all to varying amounts.


All beings (as far as I know) breathe something — some mixture of "air" that is natural to themselves.

None of our visiting races can sustain life in our atmosphere, but some can survive for a very short time here before they die, the longest is 2 hours, and that is the other race of humans who visits us.


There are other differences also such as:

• Light • Temperature • Minerals
• Pressure • Chemicals • Gases
• Gravity • Plants • Germs, etc.

See also