What you are seeing is the Mars moon, (not sure which one) passing in front of the sun. The moon is the shape of a potato. It looks like a shadow because there is no light falling on the face that is towards the camera. For the same effect, take a real potato and hold it so that it partially obscures a light bulb.I'm sure I'm revealing my ignorance here, but... why does the Sun cast a shadow which looks like an Idaho potato?
Our ideas of eclipses are skewed because the size of Earth's moon's disc is almost exactly the same size as the disc of the sun.