NASA has an open call for haiku to send to Mars aboard the MAVEN spacecraft.
http://lasp.colorado.edu/maven/goingtomars/send-your-name/Deadline is July 1st, at which point people get to vote on the submitted haiku. (Which makes this harder, as you will have to appeal to the average member of the public, as well as those seasoned in haiku.)
The three haikuists with the most votes will be asked to write haiku especially for the occasion, and all haiku will be sent to Mars on a DVD on the spacecraft. I'm going to go out on a limb and guess they'll be sticking to the 5/7/5 count pretty strictly, too.
The top three entries will also be featured prominently on the website.
A bit out of left field, but cool idea!