Guest Book On The Moon
Plant a closable metal box securely onto the surface of the moon with non-biodegradeable paper and pen too sign your name, date, or any other message in the book, as we will all (some day) be able to charter a space plane to the moon, to sign the book. The sponsor could leave an ad and charge by line in the book, or books. You could also be buried there, or leave a plaque or tile with your name or a flag of your company or heritage as long as we don't clutter the moon's surface. We could narrow it down to the essentials and I think a guest book and charge would be best, as well as the sponsor's name on the box and book.
Reward: Just a thought that would become obvious soon any way. No reward other than being the first to say it here.