Mercury transitted the sun yesterday. I looked at it using a special telescope that protected my eyes from the sun's brightness, but showed Mercury as it crossed in front of the sun.

Mariner 10 was launched by JPL in 1973 in order to reach Mercury. This was the final Mariner project, and it pioneered the use of a "gravity assist" by swinging by Venus to bend its flight path to Mercury.

Using a near-ultraviolet filter, it produced the first clear pictures of the Venusian chevron clouds and performed other atmospheric studies before moving to the small, airless, cratered globe of Mercury. Here a fortuitous gravity assist enabled the spacecraft to return at six-month intervals for close mapping passes over the planet, covering half the globe (Mercury’s slow rotation left the other half always in the dark when Mariner 10 returned).