http://www.skyandtelescope.com.au 27verified this initial discovery: the
farside is composed almost entirely of the
lighter toned, rough, and heavily cratered terrae,
with limited exposures of maria.
Thus, we learned that the Moon possesses two
hemispheres of distinctive character. This contrast
is most obviously expressed by the distribution of
dark mare deposits, but other differences (such as
the distribution of certain elements) also exist. After
more than five decades of study, we still do not fully
understand how our Janus-like Moon developed its
two faces — but we do have some clues that allow us
to speculate on this dichotomy’s meaning.‘DARK SIDE’ vs ‘FARSIDE’
Although the Moon always points one face toward Earth, the whole lunar globe
sees the Sun over the course of a lunar day. The Moon rotates on its axis once
every 708 hours with respect to the Sun, thus putting half of its surface in
darkness for 354 hours. The ‘dark side’ is merely the nighttime hemisphere. If
the dark side and farside were the same thing, we would never see lunar phases.
The conflation of ‘dark side’ with ‘farside’ might have its roots in the cultural
meaning of darkness as a synonym for ‘unknown’.TRENT M. HARE ET AL. / U.S. GEOLOGICAL SURVEY SCIENTIFIC INVESTIGATIONS MAP
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HIGHS AND LOWS The side of the Moon that faces Earth has broad lava
plains across much of its surface. Yet the other side looks totally different:
it’s covered in rough highlands, with few lava plains. These false-colour
maps are based on data from NASA’s Lunar Reconnaissance Orbiter.-9000 -7000 -5000 -3000 -1000 0 1000 3000 5000 7000 9000
Elevation in metres-30,000 -20,000 -10,000 0 10,000 20,000 30,000Elevation in feet