In pictures: Nasa releases pictures of Earth's beauty

Nasa is marking Earth Day by releasing some of its best images of our planettaken from space - by its satellites, its research aircraft and astronauts aboard the International Space Station (ISS) - in the past year. Here is a selection of them:
Flying over the Gulf of Aden and Horn of Africa
Flying over the Gulf of Aden and Horn of Africa, European Space Agency (ESA) astronaut Samantha Cristoforetti took this photo from the International Space Station (ISS)
Yellowstone national park
An image of Yellowstone National Park in the United States was posted by Nasa astronaut Reid Wiseman as he prepared for his return journey to Earth
Solar Eclipse shadows over clouds in the Arctic Ocean
Shadows from the solar eclipse are reflected on clouds over the Arctic Ocean in images captured by Nasa's Terra satellite on 20 March 2015
View from ISS of Great Lakes and Central US
The Great Lakes and central United States at night - taken from the ISS by flight engineer Barry Wilmore on 7 December 2014
Aurora
Flying through an Aurora - European Space Agency astronaut Alexander Gerst posted this on 29 August 2014
Windswept valleys in Northern Africa
Windswept valleys in Northern Africa - another photo taken by Alexander Gerst, this time on 6 July 2014
Melt Ponds in Greenland
Warmer weather melts snow and ice on Greenland's glaciers which collect in depressions on the surface to produce these sapphire-coloured ponds
Great Sandy Desert, Australia
Active dune movements in the Great Sandy Desert in north-western Australia
Iberian Peninsula
Night time in Spain and Portugal - the entire Iberian Peninsula captured on 26 July 2014