The first image (above) transmitted by the Curiosity rover from Mars was kind of blurry and unexciting. So the folks on Twitter and Tumblr substituted a more dramatic shot (below). It's circulating with the caption: "NASA just landed a rover on Mars, this is the very first picture. This JUST happened minutes ago."
It actually is a picture of Mars, but it was taken by the Mars Spirit rover in 2005. (link: gawker.com)