Rosie? I got this from the NASA website:

http://www.nasa.gov/centers/goddard/multimedia/gtv_copyright.html

NASA and Copyright Regulations

01.04.06

 

 

NASA images generally are not copyrighted. You may use NASA imagery, video and audio material for educational or informational purposes, including photo collections, textbooks, public exhibits and Internet Web pages. This general permission does not include the NASA insignia logo (the blue "meatball" insignia), the NASA logotype (the red "worm" logo) and the NASA seal. These images may not be used by persons who are not NASA employees or on products (including Web pages) that are not NASA sponsored.

If the NASA material is to be used for commercial purposes, especially including advertisements, it must not explicitly or implicitly convey NASA's endorsement of commercial goods or services. If a NASA image includes an identifiable person, using the image for commercial purposes may infringe that person's right of privacy or publicity, and permission should be obtained from the person.

 
On the face of this I would say you are ok to use their images of Mars.

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All the Woes of a World by Jonathan Icknield aka The Bryster

And in my final hours - I would cling rather to the tattooed hand of kindness - than the unblemished hand of hate...