Selenean Summit

Selenean Summit (circled) on the lunar far side.

PHOTO VIA NASA/ Goddard Space Flight Center/ DLR/ ASU

In the mid-Twentieth Century, the popular paintings of Chesley Bonestell depicted the moon’s mountains as soaring, craggy peaks.

Although the Apollo missions showed lunar mountains to be gently rounded, it wasn’t until this decade that the moon’s highest point was identified.

Bonestell’s extreme topography seemed appropriate for a geologically dead world, lacking the glaciers and weather that grind down Earth’s summits. But In fairness to Bonestell, the relentless ability of micrometeorites to soften the moon’s landscape was not yet understood.

In hindsight, it’s not surprising that the moon’s tallest elevation is not a dramatic pinnacle towering above the surrounding plain, but merely the highest spot on the rim of a crater (Engel’gardt, on the side of the moon perpetually hidden from Earth, whose overall elevations are significantly higher than the earth-facing side). The “Selenean Summit,” as measured by the Lunar Reconnaissance Orbiter in 2010, stands 35,287 feet (10,786 m) above the moon’s mean elevation (a stand-in for sea level, from which earth’s mountains are measured), 22 percent taller than Everest.

While you might expect far higher mountains on a world with one-sixth earth’s gravity, the moon also lacks the mountain-building plate tectonics of Earth. The moon’s mountains were exclusively born of impacts.

If the rounded, raised rim of crater doesn’t seem fitting to hold the title of “Tallest Lunar Peak,” consider Mt. Huygens, on the rim of Mare Imbrium, the “Man in the Moon’s” right eye. Huygens is the tallest lunar mountain from base to summit at 18,000 feet (5,500 m). Earth wins this round: its tallest mountain from base to summit is Hawai’i’s Mauna Kea, whose summit stands 33,474 feet (10,200 m) above the ocean floor.

Alaska’s Denali, the highest from base to summit above sea level, is almost exactly as tall as Huygens.

Next column: The Flying Eagle star.

Chris Anderson manages the College of Southern Idaho’s Centennial Observatory in Twin Falls. He can be reached at 732-6663 or canderson@csi.edu.

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