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Wednesday, 30 January 2019

The Moon and its dark side

A famous 1973 Pink Floyd album is called The Dark Side of the Moon. Until recently, I had never realised that we only see one (1) side of our Moon. The other ("dark") side of the moon is invisible to us. Recent Chinese images of that other side show a landscape full of craters unlike "our" side (Guardian). To some extent, our moon protects us from the impact of asteroids and meteorites.

On 25 January 2019, the science journal Earth and Planetary Science Letters published that a "sample collected during the 1971 Apollo 14 lunar mission was found to contain traces of minerals with a chemical composition common to Earth and very unusual for the moon" (Phys, EPSL, Curtin University). Note LO: bold and italic markings are mine.

Professor Alexander Nemchin of Curtin University assumes that "this piece was formed on the Earth and brought to the surface of the moon as a meteorite generated by an asteroid hitting Earth about four billion years ago, and throwing material into space and to the moon" (CU).

His assumption would confirm the so-called giant-impact hypothesis, which "suggests that the Moon formed out of the debris left over from a collision between Earth and an astronomical body the size of Mars, approximately 4.5 billion years ago" (Wiki).

On 17 January 2019, another finding revealed that "the number of asteroid impacts on the Moon and Earth increased by two to three times starting around 290 million years ago" (ScienceDaily). “The implication is that since that time we have been in a period of relatively high rate of asteroid impacts that is 2.6 times higher than it was prior to 290 million years ago.” (University of Toronto)

A moon is an astronomical object or celestial body similar to asteroids, comets, meteorites, planets and stars. The differences are based upon their:
- functionality: stars give light and warmth, like our Sun (eg, Socratic-2018);
- orbit: planets orbit a star while moons orbit a planet (eg, Forbes-2019Sciencing-2018);
- size: asteroids and meteorites are both "small" space rocks (NASA Science);
- shape: "comets are made of ice and dust—not rock" (NASA Science).

Our moon is neither common, nor uncommon: "[] many planets have these satellites. For instance, Jupiter has 63 moons, while 47 orbit Saturn while Mercury and Venus have none. [ ] Moons vary a great deal in size and shape, but most are made from the dust and gas that were going around planets during the formation of the solar system." (Sciencing-2018)

Today, our Moon is a moon as it's within Earth's gravity. However, our Moon has been drifting away from Earth by almost 4 centimeter annually, ever since that collision of 4.5 billion years ago. Hence, our Moon could once become a planet, based upon the 2006 IAU definitions.

Brain Damage a.k.a. Lunatic (1973) by Pink Floyd

And if the cloud bursts, thunder in your ear
You shout and no one seems to hear
And if the band you're in starts playing different tunes
I'll see you on the dark side of the moon


Note: all markings (bolditalicunderlining) by LO unless stated otherwise

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