Should atmosphere be capitalized in a sentence?

The word "atmosphere" is generally not capitalized in a sentence unless it's part of a proper noun or used in a very specific context.

Here are some examples:

Not capitalized:

* The Earth's atmosphere is composed mostly of nitrogen and oxygen.

* The atmosphere was thick with smoke after the fire.

Capitalized:

* The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission is studying the Martian atmosphere.

* We learned about the atmosphere in our science class. (If "atmosphere" refers to a specific course title)

In most cases, "atmosphere" is a common noun referring to the layer of gas surrounding a planet or celestial body. It's only capitalized when it's part of a proper noun, like a specific mission or title.