“Mars at midday. Or, rather, mid-sol. Welcome to Chryse Planitia, as humans first saw it 40 years ago today, when the first robot from Earth landed on the Red Planet. Viking 1 was supposed to land on July 4, the bicentennial of the Declaration of Independence, but its original landing site was too rocky. The probe orbited Mars a while longer until its human managers could find a flatter, safer spot, and this is the one they came up with. On the very same day seven years prior, humans had landed on the moon, another feat that also remains astonishing. Think about that: In less than a decade, people went to the moon and sent a robot to Mars, and we saw video of the surfaces of two alien worlds for the first time.”