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Word of the Day Wednesday, June 10, 2026

exosphere

/ɛksəˈsfɪər/ noun · British & US
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What does exosphere mean?

noun

The outermost layer of a planet's atmosphere, extending from the thermosphere to the interplanetary space. It is a very thin layer of gas that surrounds a planet.

Example

"The exosphere of Mars is thought to be composed mostly of carbon dioxide and noble gases."

Definition generated by AI and curated by RJS Tech Solutions LLP.

Synonyms for exosphere

Rhymes with exosphere

Etymologically related