It must a rock. The black dots representing eyes is a shadow or some sort of small depression. Observe the skull carefully. You will find a depression of the right side of head. It is not possible to have such kind of depression for a human skull. If was skull, it should have been rounded in that area too. One morething, it is unlikely that the black spots are eyes becoz eyes area should have been closed due to heavy dusty winds in Mars. The soil gathered in front of rock is due to obstruction caused by the rock to the dusty wind flow.