Natalie York had never even thought about Mars, other worlds, before Mariner. She wasn’t even interested in astronomy, or space travel, or other worlds, or any of that. Astronomy was a subject for the handful of old men who controlled access to the big telescopes and used them to pursue their obscure, decade-spanning projects. Even back in 1964, geology — the study of the Earth — was what captured her imagination. Stuff you could walk around in, and pick up, and examine with your eyes and hands.

Mariner made everything different. For a while, anyhow.

She remembered a teacher at school trying to put over the basics of astronomy.

In July 1964, when Mariner reached Mars, the planet had been in opposition. Like all planets, Mars circled the sun; but its orbit was outside the Earth’s, and its year was twice as long. That meant its distance from Earth was constantly changing, as Earth scooted by on the inside track. But Mars would come closest to Earth when sun, Earth, and Mars where lined up, in that order. Opposition. That’s what it means. So at opposition, Mars is almost opposite the sun, seen from Earth. At its closest point.

She remembered, as she’d learned of that, a sudden sense of herself as a passenger on the Earth — as if it were a giant spinning spaceship, steaming past that great red liner called Mars.

To do their jobs, astronomers have to be able to figure out where they are, in relation to the rest of the universe. They have to be able to imagine, really and truly, that they aren’t living on a flat Earth.

She’d gotten copies of the pictures radioed back by Mariner 4 and had indeed taped them to her bedroom wall.

The first photo showed the limb of the planet, seen from close to; the horizon curved, and surface markings were vaguely, frustratingly visible. Still, the image was a hell of a contrast to the misty, unreal disk you could see through a telescope.

Mariner’s photos showed how Mars would look to an orbiting astronaut.

The next few pictures showed views of the surface, as if looking down from directly overhead. The monochrome images looked like aerial pictures of a desert, Arizona maybe…

Ben Priest said, “You know, Mariner was a big shock to us all. Before Mariner, we thought we understood Mars pretty well. You could walk around on the surface with nothing more than a face mask. We thought we saw seasonal changes in dark patches on the surface that were maybe due to some kind of spreading vegetation.

“But now, everything looks different. We had it wrong — all of it. Earthlike, Mars certainly isn’t.”

It was Mariner’s seventh picture that was the real surprise.

The seventh picture showed craters. Nobody was expecting to find those.

Not Arizona, then. Mars looked more like the Moon.