You might think that this image looks a little bodged together, and you'd be right to. After all, it's literally a collage of photographs obtained by Voyager I—all the way back in 1979.
Collected when the spacecraft passed Jupiter's moon Io for the first time, the images were assembled by hand at NASA, revealing for the first time strange craters, smooth plains and gigantic mountains that covered the surface of the moon. More than that, though, they revealed that Io wasn't the cold wasteland that astrophysicists has believed it to be—rather, it was seething with volcanic activity.
So, while the image might not look much by today's standards, it was transformative in our understanding of the solar system. Not bad for something that looks like a kindergarten project. [New Scientist]
Image by UCL/NASA