Ansel Adams made this photograph in Grand Teton National Park in 1942, while working for the U.S. National Park Service on a project to make photographic murals for the Department of the Interior. Because it was made for the government, it belongs to the public: you can print it, share it, hang it.

Look at how he uses tone. The Snake River glints like mercury in the dark valley; the Teton range glows under breaking storm light. Adams was famous for his technical obsession — the "Zone System" he developed helped photographers control every shade from pure black to pure white.

In 1977, this image was one of 115 pictures chosen for the Voyager Golden Record, the gold-plated disc carried by the two Voyager spacecraft, which have now left the heliosphere and are travelling between the stars. If anyone ever finds them, this is one of the ways we chose to say: this is what our planet looks like.