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Astronomy with Yallajabaleya, Mt Sinai

Earth and Moon

Many still believe the moon landing in 1969 was a hoax, though the colossal conspiracy required beggars belief. And what about the 385 kilograms of moon rock stored in laboratories around the world? Such cynicism devalues a stunning achievement. Not only have we put men in rockets, space stations and lunar buggies, we have also tramped the moon and collected samples of rock which have deepened our understanding of the origin of our moon and the solar system.

Although bright in the night sky, the moon reflects only 12% of the light received from the sun. If it were shrouded in cloud like Venus it would appear 5 times brighter! The darkest areas lie in the maria where molten basalt has oozed out and covered the older pitted landscape. Basalt is common throughout the solar system and is extruded on Earth through mid-ocean ridges and volcanic activity. It forms the dark rock under Edinburgh Castle. But lunar basalt is different from Earth’s basalt. It is richer in titanium and completely free of the water that is commonly found bound to minerals on Earth.

The brighter areas on the moon are constituted by the lunar highlands, covered in impact craters. The rock here is older, far older than any rock on the Earth’s surface. It is made of anorthosite, rare on Earth, and probably formed as a light crust on an ocean of molten rock. The possibility that the moon was once molten has given rise to a dramatic new model for its formation.

It is now hypothesized that shortly after the formation of our sun and during the early evolution of the planets, over 4 billion years ago, the proto-Earth was slammed by a proto-planet the size of Mars. The heat generated by the collision caused the two bodies to melt and fuse while spraying out slush and rocks which looped round the planet in a ring. Over a remarkably short time, the liquid and rocks of the ring coalesced into a molten ball, our new moon. Once it had cooled and solidified, bombardment by meteorites, comets and any remaining fragments from the collision pock-marked the surface and caused the eruption of basaltic magma which covered the low lying regions.

This blog first appeared in the Cairo BCA Magazine for June 2009 to promote star gazing in Sinai with Yallajabaleya and an 8″ Meade LX90 Telescope.