NOTES: The Moon: Age--4.6 billion years (same as earth). Origin--early collision of an asteroid with earth, vaporizing material which condensed into the moon. Atmosphere--none. Tidal locking--same side always faces earth. The moon's denser core was pulled closer to the earth, and tidal force held it there. History--cratering billion years, volcanism billion years ago. How do we know? Dating of moon rocks (overlay). Features: Highlands--higher areas than crater floors covered with lava --called maria (singular--mare). Regolith--powdery soil pulverized by micrometeors. Rays--splayed out lines of material from large craters. Rills--solidified lava rivers in fissures. Exploration:

‘Our’ Moon

The Eternal Earth If you were on the moon: 1.The earth would hang there always in the same position. 2.The sky would be pitch black—no atmosphere. 3.Stars would not twinkle. 4.The day would be 29 1/2 earth days long.

You would need to deal with no air, and much lower gravity…

The lighter areas are the lunar highlands, the original surface of the moon The darker areas are the maria, lava beds laid down in large crater basins.

Age of the moon: 4.6 billion years. We brought back two tons of moon rocks, the oldest--from the highlands-- are that age. The age is determined by radioactive dating.

Have you ever had a radioactive date?

It’s sad, but some people only have a half life. For radioactive isotopes, their half life (time for half of them to decay), is used to determine a sample’s age.

Origin --early glancing collision of an asteroid the size of Mars with earth, vaporizing material which condensed into the moon.

How do we know? The volatile elements like oxygen, nitrogen, and hydrogen Are absent from the moon’s surface. We believe they were burned out in the heat of the impact. Then gravity condensed the vaporized particles, making rocks on the moon like those on the Earth, minus the volatiles.

The same side of the moon always faces the earth. Denser core is closer On the near side.

They differ wildly. Almost no lava beds on far side, and many more craters.

History--cratering billion years.

Volcanism billion years ago. Maria formation:

Regolith--powdery soil pulverized by micrometeors, and Still being created. An astronaut’s footprint in the regolith.

Rays material splattered in lunar impacts. The crater Proclus.

Lunar rille—solidified lava, which had flowed into lunar cracks.