The outermost part of our planet’s atmosphere extends well beyond the lunar orbit – almost twice the distance to the Moon. A recent discovery based on observations by the ESA/NASA Solar and Heliospheric Observatory, SOHO, shows that the gaseous layer that wraps around Earth reaches up to 630 000 km away, or 50 times the diameter of our planet.
Reference: Baliukin, I., J.-L. Bertaux, E. Quemerais, V. Izmodenov, and W. Schmidt. SWAN/SOHO Lyman-alpha mapping: the Hydrogen Geocorona extends well beyond the Moon, J. Geophys. Res. Space Physics, 124. https://doi.org/10.1029/2018JA026136