Dim sun

It’s nearly the middle of January, and the Earth is around 438 million years old. Woohoo! In fourteen days I’ve survived the crushing hail of planetesimal conglomeration, the searing heat of a collision with Theia, and the buckling, vomiting red and black mayhem of the early Hadean Era. We’ve got an iron core, a peridotite mantle, a basalt crust, and a liquid ocean. What a planet.     

But the Sun these early days is dim. 25% dimmer. Or thereabouts, who can say. It’s not unlike, I suppose, the feeble January sun here in New England. Somehow the sun takes on the color of the salty asphalt, especially on days overcast with cold, grey clouds. So my wife and I are going to southern California for a few days to see an old friend — and the sun. 

The early Earth has no such option, because California doesn’t exist yet. (On this time scale, it won’t get made ‘til May.)

But it’s warm on the early Earth. There is liquid water. It’s not an ice world. Are Earth’s early volcanoes offloading a heap of carbon dioxide into the atmosphere, trapping more heat? Sigh, we know how that works. That’s probably it. (Ask Venus.)

And Robert Hazen writes, “another hypothesis places a large amount of the potent greenhouse gas methane in the early atmosphere. A curious consequence of a methane-rich atmosphere would have been chemical reactions high in the atmosphere, where ultraviolet radiation would have triggered the synthesis of a rich variety of organic molecules, including possible building blocks of life. Such organic molecules might have caused a thick, smoglike haze, transforming the blue Earth into a distinctly orange world...” 

Smoglike haze? Los Angeles here we come. Who knows what creatures you’re conjuring in your clouds. 

Earth, en route to Los Angeles.

Earth, en route to Los Angeles.