Sometime last week, the Mars Curiosity Rover, the two-year-old American craft about the size of a minivan, turned its camera skyward. There, over a dune, it saw a shining evening star that was no star at all.
It saw us—it saw Earth.
Our home planet, with us aboard, shines a little brighter in the sky on Mars than Venus does here. In the picture from last week, Curiosity can see both the Earth and the moon. Neither twinkles, like a star would; they both shine, reflecting the sun’s light.
NASA has processed the images to remove the effects of cosmic rays. But seeing the Earth and the moon would be easier on Mars than it seems from the picture above.
“A human observer with normal vision, if standing on Mars, could easily see Earth and the moon as two distinct, bright ‘evening stars,’” reads the agency’s website.
Curiosity isn’t the first rover to see Earth from the surface of Mars. In 2004, the American rover Spirit saw a shining Earth in the dawn sky. The quality of its picture wasn’t as good as the one above, though. “Earth was too faint to be detected in images taken with the panoramic camera's color filters,” a specialist wrote at the time, so the images released were black and white.
In the pictures from last week, though, Earth can be seen glowing in a dark blue sky. It makes me think about scale. In the late 1960s, activists hungered for a “whole Earth” picture of our home planet. We now have many pictures like that—photographed from orbit, like imagery in Google Earth, or from the edge of the solar system, like Carl Sagan’s famous “pale blue dot.”
Below, I’ve arranged and annotated those pictures. All are Earth; each was taken by a photographer a little more distant.
via Charlie Warzel