Wednesday, August 25, 2010

Lobate Scarps Reveal that the Moon is Shrinking

One way to open a jar which has a stuck lid is to run hot water over the metal top.  The heat from the water cause the metal to expand ever so slightly and thus lessen its grip on the jar.  Later, as the metal cools, it will shrink back to a smaller size.  The same holds true for all metals including those in the cores and mantels of planets and moons.

Our Moon's size and composition of metals olivine and pyroxene has doomed it to a life of inactivity compared to the Earth's active geology.  The Moon's mantle and core, under less pressure-induced heat than the heavier Earth, has been cooling down at a rate much faster than our planet. This is causing the metallic-comprised Moon to shrink.  Scars known as lobate scarps, caused by the crust compressing in on itself as it slowly sinks towards the Moon's center, are being found all over the Moon.

Fans of the moon need not worry.  While the shrinking is recent on the selenological (Moon geology) timescale, the Moon's shrinkage has yet to have any noticeable affect on the Earth and will not have one for possibly millions of years.

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