The view from space of our planet's most impressive natural and constructed landmarks is striking, and not just on this year's Earth Day.
The long and winding Grand Canyon; the European Union's longest river, the Danube; and the 13,000 miles of the Great Wall of China become almost abstract works of art when photographed from space.
NASA astronaut Victor Glover Jr., who conducted his third spacewalk in late February, talked then about how fragile Earth looks from space, and "just how special it is for there to be human life on this planet."
"It makes me want to do all that I can to protect that," Glover said.
Many of the photos shown here were shot by EarthKAM, a project started in 1995 by the late Sally Ride, America's first woman in space. It was first called KidSat. It allows middle school students around the world to ask for images of locations on Earth.
The EarthKAM camera flew on two more shuttle flights before moving to the International Space Station in 2001, according to NASA. Sally Ride died in 2012, and NASA renamed the program Sally Ride EarthKAM the following year. It remains a permanent payload on the ISS.