An Eclipse on Mars

The scientists who thought to pan up with the Curiosity Martian Rover were impossibly cool. Here is an eclipse as seen on Mars, as recorded by Curiosity. This is what we call on earth an annular eclipse, in which the diameter of the moon, in this case Phobos, combined with its distance from the surface of the planet, make it too apparently small to cover the entire disk of the sun.

As to total eclipses, we are incredibly lucky to be alive on Earth just now. Part of my most recent book Out in the Cold covers a trip my wife and I made to Svalbard, chasing the total solar eclipse of March 2015. To quote from the book:

“Total eclipses are possible only because the sun’s diameter is about 400 times that of the moon, while the moon is about 400 times closer to earth, allowing for the moon’s disk to just about cover the sun’s. Consider the serendipity.

Further, we just happen to be here at the right moment in the cosmos. The moon’s orbit drifts about four centimeters a year away from earth. Scientists have measured its retreat using tools left on the moon by the Apollo program. A billion years ago all eclipses entirely blotted out the sun, and in just fifty million years the moon will be too small when viewed from earth to ever cover the sun. Even now it barely does. If the moon’s diameter were just 169 miles smaller total eclipses would be impossible.”

To everyone who saw today’s eclipse and was a little awed, cheers!