Actually the convention for all mapping of solar-system bodies in the pre-space-probe age was to use astronomical definitions of East and West, so the compass was flipped (but since the maps were drawn from telescopic images and the astronomical telescopes in use tended to invert the view, maps by Northern Hemisphere astronomers would often in practice do this by putting East in the normal place but South at the top).
Today, when good data will often come from space probes rather than Earthbound telescopes, that convention's been abandoned and the general convention is to map them all like we do the Earth, with East clockwise from North.
I was going to say that it's relative to the body's rotation, but that's not always true: Venus's (slow) rotation is retrograde, but IAU conventions align its north with solar-system north and take its axial tilt as 3 degrees, not 177 degrees.
Star maps still seemingly have the east-west axis pointing the "wrong" way because they're still looking up instead of down, with directions projected up from the Earth.
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