... Aurora Over Alaska . ... Are those green clouds or aurora? ... Rolling Across the Rocky Plains of Mars . ... To find out, scientists have been studying images taken by the robotic Venus Express spacecraft when it passes over the lower spin axis of Earth's overheated twin. ... To help find out, scientists have sorted through hundreds of infrared images of Saturn taken by the Cassini spacecraft for other purposes, trying to find enough aurora images to correlate changes and make movies. ...