NASA just released 2.95 million satellite images to the public - here are 21 of the best

An instrument called the Advanced Spaceborne Thermal Emission and Reflection Radiometer - or ASTER, for short - has been taking pictures of the Earth since it launched into space in 1999.

In that time, it has photographed an incredible 99% of the planet's surface.

Although it's aboard NASA's Terra spacecraft, ASTER is a Japanese instrument and most of its data and images weren't free to the public - until now.

NASA announced April 1 that ASTER's 2.95 million scenes of our planet are now ready-to-download and analyze for free.

With 16 years' worth of images, there are a lot to sort through.

Here are our 21 favorites.