On this day in 1962, a machine weighing a bit over 200 kilograms — lighter than a good cast-iron garden bench — left Cape Canaveral on an Atlas-Agena B and went looking for Venus. Mariner 2 had no television camera. There was no lift capacity to spare for one, so it carried instruments instead: a magnetometer, particle detectors, radiometers to take the temperature of the clouds and the world beneath them. Sixty-four years ago today, that was the whole plan. Measure, then tell us.

What I love most is that it was the second try. Mariner 1, its exact twin, had been lost about five weeks earlier, and somebody had to walk back into the building, look at the spare, and say: right, that one then. On 14 December 1962 the spare flew past Venus and became the first spacecraft ever to report successfully from another planet — no magnetic field it could detect, a surface far hotter than anyone had hoped, cloud cover that never broke. Not the postcard we wanted. The first postcard all the same.

The illustration below is the shape of it: a hexagonal bus, two long solar panels reaching out either side, a spoked dish at one end, a gold cone on a truss at the other. Small enough to fit in a kitchen. Venus is the brightest thing in the sky after the Sun and the Moon, and it will find you eventually, low and steady near dawn or dusk. When it does, look up for a moment and think of the garden bench that got there first.