Dr Kursawi Ginsang devised a table for quick reference and classification of celestial bodies.
The sysetm is based on a progression series from A to Z.
At the top end of the scale "A" is an optimum sterile environment suitable for even the most sensitive of surgical or electrical operations.
"Z" is the bottom end of the scale from which there is no known protection against harm or hazard, an environment that is, by known science, completely unaccessible and totally hostile.
The full scale and related examples are as follows:
A - Sterile artificial environment fully controlled.
B - Sterile artificial environment partially controlled (Climate controlled environment).
C - Semi-Sterile environment partially controlled or environment with extremely moderate conditions. (Temperate zone of Earth during moderate summer)
D - Marginally controlled environment or environment with seasonable atmosphere. (Temperate zones of Earth during spring/fall).
E - Uncontrolled Environment, an environment which is tolerable to human existence with a minimum of precautions. (Temperate zones of EARTH)
F - Any environment which is at either end of normal human tolerance, an environment where protection is recommendated for survival and required for comfort. (Equitorial region or Arctic region of Earth or Earth during much of Eco-Crisis)
G - Mild Exposure risk, environ requiring at least a minimal amount of protection against exposure for habitation.
H - Moderate Exposure risk, requiring moderate protection for survival.
I - Extreme Exposure risk, survivable under short term exposure with a moderate amount of protection.
J - Extreme survivable even short term if unprotected (Mars)
K - Unsurvivable without minimum level one environmental suit (Titan)
L - Hostile (level two space suit with environmental support required)
M - Very hostile (space suit with full support) (Terran MOON)
N - Extreme hostile (short term space suit barely tolerable even with full support)
O - Oppressive even with full support. (MERCURY)
P - Maximum support required due to environmental extremes. (PLUTO)
Q - Hostile environment even to space suited individuals (Light Corrosive or Pressure extremes)
R - Hostile environment even to sheltered individuals (Moderate Corrosive or Pressure extremes) (VENUS)
S - Hazardous environment even to well sheltered structures (High Corrosive or Pressure extremes) (NEPTUNE)
T - Extreme Hazard environment (Intense corrosive or pressure extremes) (URANUS)
U - Extreme environment / Probe study only (SATURN)
V - Extreme environment / Probe study marginal. (JUPITER)
W - Extreme environment / Probe study beyond initial entry unlikely to succeed.
X - Extreme environment / Minimal Probe study possible (SOL).
Y - Probe study possible from Orbit only.
Z - Absolutely inhospitable environment. Study impossible from any reasonable range. (BLACK HOLE)