Magazine article Natural History

New Moon

Magazine article Natural History

New Moon

Article excerpt

The Moon reveals just one side to its admirers on Earth, yet our satellite seems an object with a thousand faces. It smiles with romantic light and winks at armchair space travelers. For me, most of all, it is the place where the Apollo 11 astronauts set foot in 1969, when I was eight. But as an adult, I also see it as our planet s dynamic partner, without which life on Earth would never have flourished. Isaac Asimovs "Triumph of the Moon" (at mountain man.com.au/Lasimov.html), written shortly after he watched the launch of Apollo 17, sets forth his reasons for thinking we would not have evolved without the Moon, and how the Moon was crucial to the development of mathematics, science, and space travel.

The Moon, as the leading theory goes, was born in the aftermath of a titanic collision between a Mars-size planet named Theia and the early Earth. A Web page at the Planetary Science Institute introduces the "giant impact" hypothesis with paintings by William K. Hartmann, one of the astronomers who originated the idea in 1975 (psi.edu/projects/moon/moon. html). Alistair G.W. Cameron, another pioneer in the study of giant impacts, has a site at xtec.es/recursos/astronom/ moon/camerone.htm with a number of his early computer simulations of the collision.

Collision theories also enliven Web pages by G. Jeffrey Taylor of the Hawai'i Institute of Geophysics and PlanetolOgy (www.psrd.hawaii.edu/Dec98/Origin EarthMoon.html) and H. Jay Melosh of the University of Arizona in Tucson (www.lpl.arizona.edu/outreach/origin). Their simulations show lighter mantle rock from both bodies blasted into orbit, while Theia's dense iron core merges with that of the proto-Earth to form our planet's present massive core. That core was key to life's overwhelming success: a smaller core could not have generated a magnetic field strong enough to shield us from lethal cosmic rays. …

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