An astronaut (say a NASA astronaut from the ongoing Curiosity project or any such in the future) who dies on / on his way to / on his way back from / because of something related to his/her journey to/from MARS, which is for the sake of Science/Astronomy/humanity.
Of course, I doubt about any need to elucidate it. Play with the words 'Mars' and 'martyr' is all it is. This is a word of the future!
Hope there won’t be any Marstyrs :)
This new pioneering NASA project is gonna create a lot of Marstyrs because of its deadly mission conditions.