Question 10. what physical entity needs to be present to allow liquids on the surface of planetary bodies? hint: think about the word associated with one of the units used for pressure - "atm". il p

Atmospheric pressure

Explanation:

Atmospheric pressure is not a physical entity it can as the air can be felt not seen, Its present in all forms of matter either solids, liquids or gases, etc. Present on all planetary bodies except some planets that does the atmosphere like that of the earth but have gravity and density. Atmospheric pressure is a unit for measuring the pressure from the mean sea level form average pressure is 1013 millibars. But studies have revealed that mars may have large bodies of oceanic mass underneath it as the presence of ancient oceans has been found on the red planet which indicated that due to the drying of the river mars rivers may have disappeared.  As pressure varies with altitude and also depending on the composition of natural gases in the environment like Oxygen.