It’s the middle of the night at JPL, and the usual dozens of deer are on their nightly foraging rounds across the campus. Mars is up. So is the Moon. And so are nine machinists in the lab’s high-precision fabrication shop, working the second shift that ends between midnight and 3 a.m. They are part of the round-the-clock team turning out odd-shaped pieces of metal that will become robots destined for Mars.