THE MOON (LUNA) - BASIC PHYSICAL DATA

LUNAR RADIUS
Polar      = 1736.0 km = 1078.7 mi
Mean       = 1737.1 km = 1079.4 mi
Equatorial = 1738.1 km = 1080.0 mi

GEOCENTRIC DISTANCE
Min  = 363301 km = 225745 mi = perigee
Mean = 384401 km = 238856 mi
Max  = 405502 km = 251967 mi = apogee

SURFACE GRAVITATIONAL ACCELERATION
1.63 m/sē = 5.37 ft/sē

MOON/EARTH SURFACE GRAVITY RATIO
1.63 / 9.81 = 0.166
This means that on the moon, any person or object would have only
about 1/6 as much gravitational weight as experienced on Earth.

LUNAR ESCAPE VELOCITY
2.38 km/s = 1.48 mi/s = 8570 km/h = 5330 mi/h

MEAN LUNAR SURFACE TEMPERATURES
During the Day   =  107 C  =  +227 F  =  380 K
During the Night = -153 C  =  -243 F  =  216 K
The Earth is only about 4 times larger than the moon, but contains some 81.3 times more material mass.  At its surface, the moon has about 1/6 the gravity of Earth.  There is no air mostly due to the low gravity being insufficient to retain an atmosphere in such close proximity to the sun and no means of sufficient replenishment even if it did at one time.

If the moon was given an atmosphere similar to ours and then left to nature, what would happen?  The sun would rapidly deplete any atmosphere as the gas particles reached escape velocity and evaporate away into space in the low gravity and intense solar radiation.  Without replenishment, the surface environment would quickly become a near total vacuum, like it is now, not much different than outer space.

To retain an atmosphere, the gas particles must not be able to simply evaporate away into space over time.  If our moon was sufficiently far from the sun, where it was much, much cooler, like at the distance of Pluto or beyond, then it would indeed have the ability to retain a very tenuous atmosphere close to its frigid surface.



Jay Tanner - 2012