An equinoctal moon

Luna glided overhead as we looked for nightjars. It was easier to spot the triad of lunar seas, serenity, tranquility, fertility, than a savanna nightjar in flight. Certainly photographing them at night with my equipment was out of the question, even with the moon waxing to nearly three quarters. I turned my camera up to the moon.

Top to bottom: Seas of Serenity, Tranquility, and Fertility (detail)

The lunar seas of showers and of clouds had become visible a couple of days ago. These fancifully named seas are actually basalt shields, the frozen remnants of lava flows which were caused by an extensive bombardment by meteors around four billion years ago. The earth was also shaped by this shower, and very few fragments of continental crusts are older. Life began on earth soon after that. On the moon the lava seas in these enormous craters had solidified more than three billion years ago. By that time photosynthesis had begun on earth. Our atmosphere was changing even as the splotchy appearance of the moon took shape. The new photosynthetic life made the earth unlivable for most anaerobic bacteria and caused the first age of extinction.

Plato crater at lunar dawn, just north of the Sea of Showers (detail)

Near the northern end of the terminator, my camera could pick out the far edge of Plato crater catching the morning sunlight. This crater is as old as the sea of showers (Mare Imbrium) just south of it. If you were to stand inside that crater then and looked up at the cliffs on the far edge, what a sight the morning sunlight must be! At the southern end of the terminator you can see a jumble of craters. Just inside it, at roughly mid-morning, is the bright young Tycho crater, only a 108 million years old. The dinosaurs may have seen it forming. In a few days, the whole of the visible half of the moon would have day. That lunar day is what we call a harvest moon. It was still more than a week away.

In the next two days we were to cross the Tropic of Cancer several times, as we scouted for more of the winter’s birds passing through the Rann of Kutch. It was a funny astronomical coincidence. The Tropic of Cancer marks the furthest point north where the sun can be at the zenith. And we were near that at the time the sun was crossing the equator! As I took photos of the signboard someone remarked that it had seen better days. True enough. So had the moon, by my reckoning.

%d bloggers like this: