Hirise images & the choice of place to photograph

Hi all,
I was wondering why in Hirise images of Mars (look at map at
http://marsoweb.nas.nasa.gov/HiRISE/hirise_images/) we still haven't
seen photos of the South part of the planet.
In particular I'm referring to interesting zones, such as the ones with
the enigmatic "trees", "lakes" and "bushes"
(http://mmmgroup.altervista.org/e-trees.html). We have A LOT of MOC
images showing what someone identifies as "bushes", but only the Hirise
photos could solve this enigma, why don't they take pictures of those
zones? What are they waiting for?

Do they fear to eventually discover vegetation on Mars? (that would
mean a demolition of a part of the scientific establishment, of
course....). I'm getting angry..... :-(