Salt Pans and Lunar Seas

as11-40-5851 — *Lunar surface; Apollo 11 (70mm Hasselblad). Image credit NASA*

1 Feb 2018

“Beautiful, beautiful. Magnificent desolation.” Thus Buzz Aldrin described the Moon.

I love observing the Moon, and often, when I am meandering around on it with my telescope, Buzz Aldrin’s lovely words come to mind, because like many observers, I look at the Moon’s vast maria and wonder what it was like to stand there and look out at that magnificent desolation.

I got a feel for his words up here in the Askham area of the Kalahari when my dog Waldo and I spent the day out on a gargantuan Kalahari salt pan called Hakskeen Pan.

Most of the Kalahari remains arid and untouched, as it has been for about 60 million years; the landscape incredibly desolate and isolated; dominated by the red fossil sand dunes that average a height of 35 metres and rise above the vast sea of grasses. Within these dunes and grasslands lie a complex of vast flat salt pans. Unbelievably stark and harsh, they are one of nature’s most awe-inspiring sights.

It’s an experience like no other to stand on a surreal and visually immeasurable empty flatness where the horizon simply disappears in a foreverness of baked sand and salt that melts into the sky in a thin, quivering mirage right on the edge of visibility. The only sound is the faint breeze blowing across the sand; it sounds like a faraway Gregorian chant.

The geology and history of the salt pans is fascinating. Salt pans are always found in arid areas with flat topography, low annual precipitation and long dry seasons with occasional flood events. The average rainfall in the Kalahari is around 200 mm per annum (and often is considerably less). The summer thunderstorms can be incredibly dramatic and much of the annual rainfall may, almost unbelievably, occur once off and within a few hours. The pans are flooded, but within days or weeks the water evaporates in the intense Kalahari heat, leaving behind minerals precipitated from the salt ions dissolved in the water. Over thousands of years, the salts accumulate on the surface.

The mud and salt deposits are baked rock-hard by the Kalahari sun, and the salts glisten crystal white in the sun.

Waldo and I were very fortunate as there had been a massive summer thunderstorm a few days before, and the upper half of the pan was still flooded.

The edge of the flooded area. Hakskeen Pan is huge; over 140 square kilometres. And it is is very flat. A survey of the pan, measuring the elevation level at 200 points, each 10 metres apart along a 2 km long straight line, revealed that the total variation in elevation on that strip of desert is only 61 mm… that’s about as flat as it gets.

The end of the road. (The nights we have gone observing on the pan we drive straight out into the middle of the salt pan; it was thrilling to see it flooded.)

By mid day the sun was searing, the dazzling light as pale blue as if it had flowed through crystal.

It was simply awe-inspiring.

But already, although the tremendous rainfall had occurred just days before, the pitiless Kalahari sun had evaporated great swathes of the flood –

“Beautiful, beautiful. Magnificent desolation.”