Aliens man

I said this the last time people saaid that on this version of the picture, and I'll say it again here.

Gravity has a pretty long reach. The planet, moon, or any other body doesn't have to be in frame for it to act on the alien.

Secondary less likely explanation: It's a comic. Physics don't apply.

No significant gravity in space? Are you crazy mate? What keeps the planets in orbit. What keeps the moon in our orbit. You don't need to be in the atmosphere to experience gravity. If someone from the ISS just left the structure, they would begin to fall and fall and fall until they hit the earth's atmosphere where they would either burn up (But considering their comparatively slow speed, they likely wouldn't have any problems like that) or finish plummeting to the ground.

They could be just barely leaving earth and have not exited the atmosphere yet so