|MadSci Network: Astronomy|
The short answer is no! In our solar system, Mercury does not have an appreciable atmosphere and Pluto has a very thin one only when closest to the Sun. Whether a planet is able to hang on to its atmosphere is mostly dependent on its size. On Earth, the 'escape velocity' is around 7 miles per second -- in other words, any molecule of gas moving at more than this speed will escape permanently. On Mars, where the escape velocity is much lower (around 3 miles per second) as the planet is smaller, the atmosphere is much thinner, much having been lost long ago.
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