NASA is a taxpayer-supported agency, so these images appropriately have been placed in the public domain. They can be used for most purposes (that's you, bloggers!) without prior permission as long as they aren't copied in a manner implying NASA's endorsement of a particular product.
If you're in need of space & aeronautics images, GRIN should be one of your first stops. You'll find the same photos spread elsewhere across the web, as happens to public domain, but GRIN presents them with the original detailed captions and in astoundingly high resolution.
This 1999 image from NASA's Hubble Space Telescope and its Wide Field and Planetary Camera 2 (WFPC2) shows the unique galaxy pair called NGC 3314. Image credit: NASA.
NASA research pilot Bill Dana takes a moment to watch NASA's NB-52B cruise overhead after a research flight in the HL-10. Image credit: NASA
The views expressed are those of the author(s) and are not necessarily those of Scientific American.
ABOUT THE AUTHOR(S)
Alex Wild is Curator of Entomology at the University of Texas at Austin, where he studies the evolutionary history of ants. In 2003 he founded a photography business as an aesthetic complement to his scientific work, and his natural history photographs appear in numerous museums, books and media outlets.