1994

High surface concentration of FeO occurs where volcanic

basaltic lavas (mare basalts) flooded giant impact craters.

Low-FeO areas correspond to primordial (highlands) crust of

anorthositic plagioclase (about 50 km in thickness).

Clementine 1994 (analyses

of reflectance variations)

Surface of Mercury

Surface of Venus

Surface of Venus (radar image)

Galileo published his observations in Sidereus Nuncius in March 1610

Galileo originally called the Jupiter's moons the "Medicean planets", after the

Medici family and referred to the individual moons numerically as I, II, III and IV.

Galileo's naming system would be used for a couple of centuries. In the mid-

1800's the names Io, Europa, Ganymede and Callisto, would be officially adopted,

after it became very apparent that naming moons by number would be very

confusing as new additional moons were being discovered.

HST (Hubble

Space

Telescope)

image of

Uranus taken

in 1998

showing

clouds in the

northern

hemisphere.

Atmosphere

mostly

hydrogen

(H2) and

helium (He),

with a small

amount of

methane

(CH4) that

gives it a

blue tint.