Up to how far from the Moon is the Moon's exosphere gravitationally bound to it? For the Earth's exosphere it is 120,000 mi (190,000 km) or half the Moon's distance from the Earth, beyond that the Earth's exosphere is cast away by solar wind, the atoms reach escape velocity. What's the equivalent value for the Moon's gas atoms?
The Moon's exosphere is discussed in the following, but there doesn't seem to be an answer in them:
- Wikipedia: Moon's exosphere
- Space.com Atmosphere of the Moon
- Space.com Helium Spotted in Moon's Wispy Atmosphere
- Wikipedia Atmosphere of the Moon
The slim, bright crescent, known as the Lunar Horizon Glow (LHG) was glimpsed several times during Apollo missions. This picture was taken with the Clementine spacecraft, when the sun was behind the moon. The white area on the edge of the moon is the LHG, and the bright dot at the top is the planet Venus. (Image credit: NASA)