Surely we can hope that someday NASA will grant landscape architects access to the Phoenix Mars Lander, specifically to its multi-million dollar garden ho, if only to make intentionally artistic marks on the cryoturbated terrain of Vastitas Borealis.
When the spacecraft's primary goals have been achieved quite awhile back and in fact have been exceeded exponentially, surely scientists and mission administrators will universally agree then that the scientific return of its instruments — at the very near end of their operational life — can be outweighed by purely creative pursuits.
If not the Phoenix, then perhaps either of the two rovers, Opportunity and Spirit. They are certainly two of the best landscape photographers working anywhere, comparable to Ansel Adams, but they could also carry on the artistic and philosophical endeavors of Michael Heizer and Robert Smithson.
With their extendable rock abrasion tools, one can have a field day excavating swales in mathematically precise parallel rows that may or may not foreshadow the coming terraforming activities of terrestrial exiles. At the moment neither delineating accessibility and inaccessibility or co-opting distant terrain under one's control but perhaps soon there will be Martian ha-has marking territorial claims while simultaneously constructing views for the sole enjoyment of the privileged class in a socioeconomically stratified new world.
Or with their set of wheels, one can make patterned incisions in some patch of sandy soil. They seem to recall Richard Long in the beginning but a snapshot by the Mars Reconnaissance Orbiter later reveals that they are the outlines of future cul-de-sacs. The sad origin of Martian urbanism.
How about piles of rocks? Each one given names so as to weigh them down with cultural signification?
Or maybe none of the above because you consider these iconographies as ancient and irrelevant vocabularies. In which case, we wait to see what you come up with.