On an Earth-like planet, can I have a natural satellite in a stable orbit so low that it shares an atmosphere with the planet?

  • 4
    $\begingroup$ Unfortunately the moon wouldn't even be able to get that close to a planet in the first place, on account of the Roche Limit. Basically, large satellites get torn apart by gravitational forces if they orbit too close. $\endgroup$ Jan 18, 2018 at 20:36
  • $\begingroup$ Similar questions was already asked and answered on astronomy stack. $\endgroup$
    – Mołot
    Jan 18, 2018 at 20:46
  • $\begingroup$ I haven't read the linked questions in full, but I want to point out that this question may not be a duplicate as it A) Doesn't specify a planet type. B) Asks "how close?" as well as "can it be this close?" But I'd have to check the others to be sure. $\endgroup$
    – Random
    Jan 18, 2018 at 21:54
  • $\begingroup$ The size of the satellites is indeed largely irrelevant. They should be visible from the ground, though. $\endgroup$
    – Crissov
    Jan 18, 2018 at 21:59
  • $\begingroup$ @Era The question within the body does not ask about general proximity, it asks if the two bodies could share the atmosphere. That question has been answered in two ways. $\endgroup$
    – rek
    Jan 18, 2018 at 22:52

1 Answer 1


No, if it shares an atmosphere with the planet then air friction will quickly cause its orbit to decay and it will crash into the planet. That’s why satellite orbits decay.


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