Planetary Atmospheric Pressure

The media often overlook how many things have to be “right” for life to exist on a planet. Planetary atmospheric pressure is one factor.

By “life,” we mean the standard textbook definition of organisms that can move, breathe, respond to outside stimuli, and reproduce. The problem is that many conditions make other terrestrial planets (planets with hard surfaces) unlikely to harbor life. Life is even less likely on Jovian planets that are primarily gaseous. You can postulate balloon-like living organisms in Jupiter or Saturn’s atmosphere, but radiation and electrical problems make that unlikely as well.

Planetary atmospheric pressure depends on the weight of the gases above a planet’s surface. The air pressure on Earth’s surface is 14.696 pounds per square inch a sea level. That pressure allows water to exist as a liquid, and it will enable various gases to dissolve in the water. We all know what happens when you shake a bottle of carbonated beverage and then quickly remove the cap. The sudden drop in pressure causes an explosion as the dissolved carbon dioxide escapes from the liquid. For organisms to absorb oxygen dissolved in water, which fish do, the atmospheric pressure must be high enough for the oxygen to dissolve. The atmospheric pressure on the surface of Mars is .01 of the pressure on Earth. That means water on Mars would contain no oxygen or dissolved gases.

There has been discussion about finding water on the Moon or Mercury, but those atmospheric pressures are considerably lower than those on Mars. That means water would not be in a liquid state. On the other end of the pressure spectrum is Venus, where atmospheric pressure 92 times greater than on Earth. At that pressure, toxic gases would be dissolved in any water that existed on the planet.

Planetary atmospheric pressure is just one more variable that must be carefully and precisely chosen when constructing an environment that will support and sustain life. The creation is far more complicated than most of us realize. As we learn more, we must stand in awe of the God who created our planet.

— John N. Clayton © 2021

Data from Astronomy magazine, February 2021, page 10.