Figure 1 – Images of the moon Phobos eclipsing the sun on August 20, 2013 from Mars Rover Curiosity. From NASA and in the public domain.

Here go those gorgeous robot eyes again!  Thank you to reader Howard for alerting me. During last summers imaging session,  Mars Rover Curiosity shot a stunning set of images of Mars moon Phobos eclipsing the sun.  Three of those photographs can be seen in Figure 1. And you can also watch a video of the eclipse.

So a couple of points.  Earth’s moon, aka “The Moon” and sometimes “Selene.” by rare happenstance is exactly 110 X it’s diameter from the Earth as is the sun.  This results in the remarkable eclipses, where the moon’s shadow perfectlu occludes the sun’s light and we see solar flares and the suns outer atmosphere or corona.  All very beautiful.  Phobos is irregular shaped and has a diameter of ~ 11 km, It orbits around 6000 km above Mars surface. Compare that to our moon, which orbits at 384,400 km.  As a result even though the sun is much farther away from Mars, Phobos does not manage to complete occlude the sun.  We have instead an irregular shaped rock beautifully outlined against the sun’s disk.

Before you think of Phobos as a diminutive little thing, I would remind you of the origin of the name Phobos and that of his twin brother the other moon of Mars, Deimos. These were the sons of Ares or Mars. Deimos was the god of terror.  Phobos was the god of fear. (Hence phobia).  They accompanied Mars, the god of war, into battle driving his chariot relentlessly forward.