"If you turn away from the natural gifts that God has given you, or the universe has given you, you're going to grow old too soon."
- Ray Bradbury

There is another illustrative use in Static, a short story by Kent Casey in May, 1938 Astounding:

Young shavetails* - hadn't even got a space tan yet - insisted on being chummy...

(For those who don't know, a "shavetail" is a newly minted second lieutenant, deriving for the word for a newly broken-in pack mule.)

Edmond Hamilton used a variant on this idea in his 1940 story Revolt on the Tenth World:

Jimmy Crane’s voice was hoarse with passion, his worn, space-bronzed young face quivering...

When they entered the lighted cabin of the craft, which was crowded with piled sacks and metal cases, a wiry old Earthman got up, stretching and yawning. His sparse hair was pure white, his face bronzed and seamed like leather by long exposure in space to unsoftened radiation.

By the time Robert Heinlein uses it in his 1941 novel Methuselah's Children it has lost its hyphen - see space tanned.

On the other hand, maybe Venusians tan more easily than Earthmen...

Here's another example from Terminus (1961) by Stanislaw Lem:

Sims was a young, lean man with squirrelish features, a nervous cough, and flickering eyes. One glance at Boman was enough for Pirx to know that he was dealing with a space veteran. His sunburned face had that peculiar orangish tint that comes from prolonged exposure to cosmic radiation.