2. THE ORIGIN OF THE MOON
3 hypothesis:
1. The moon was originally a small planet orbiting the Sun that
approached the Earth and was captured by its gravity
2. The Moon and Earth were “twins,” forming side by side from a
common cloud of dust and gas
3. The young Earth initially spun enormously faster than now and
formed a bulge that ripped away from the Earth to become
the moon
12. Maria – basalt, a dark congealed lava rich in iron, magnesium and
titanium silicates
- Mare rocks are about 3.1-3.9 billion years old
Highlands – rich in calcium and aluminum silicates based on rock
samples collected by lunar astronauts
- less dense than mare rock and considerable older (about 4-4.4
billion years
Craters – rugged pits with large number of circular features
- made by impacts of solid bodies striking the Moon
13. Rays – light streaks radiating outward from many craters
15. MOON’S ROTATION AND ORBIT
Synchronous rotation – the Moon does turn on its axis relative to
the stars, but with a rotation period exactly equal to its orbital
period
- it keeps one face toward the planet
ELEVATIONS WERE MAPPED BY CLEMENTINE SATELLITE. MARIA ARE AT LOW ELEVATIONS FOR THE NEAR SIDE. THE AITKEN BASIN IS THE LARGEST IMPACT FEATURE HAS LOWER ELEVATION ON THE FAR SIDE
SEA OF TRANQUILITY – MARE (SINGULAR FOR MARIA)
rays represent material ejected from the crater upon impact by the object that created the crater. Studies of volcanic ejecta on the Earth show that the ejecta often comes out as narrow, fan shaped plumes which lead to narrow 'fans' extending outwards from the caldera. This explains why rays exist at all, in terms of the tendency of impact and volcanic ejecta to form these narrow, vertical plumes
