http://www.wretch.cc/album/show.php?i=lin440315&b=15&f=o1371325572.jpg&p=0
http://www.flickr.com/photos/hortonheardawho/2315348178/sizes/o/
http://www.wretch.cc/album/album.php?id=lin440315&book=15
The above links (or here, here, and here) show unmistakable structures
of osteon remains and other fossils, including a frog, on Mars. They
are unmistakable because there has never been any instance of natural
organic or inorganic structures, except osteons, that show not only
clustered but also overlapping units of black concentric rings with a
hole and a stick-up thread-like object at the center. On earth, there
is no
such kind of pseudofossil or organic tissue except osteons. They are,
in a word,unique.
The best way to prove or disprove my claim is to show above pictures
to an anatomist, a botanist and a geologist without disclosing its
Martian origin.
To be honest with you, I believe NASA will be the last one to admit
there was animal life on Mars. They will avoid the question or delay
confirmation as long as they could.
The reason is "the vested interest of NASA". You know that NASA's
budget requires them to make all the preparations for "unmanned round-
trip" missions and "manned" missions.
If fossils are found by Spirit or Opportunity, NASA will be under
pressure (especially from American Society of Physicists)
to abandon or scale down all those preparations for "manned missions".
Regarding the blueberries, they and their central holes could be
formed by electric discharge or electric arc when the Martian window
of life was closed around 2.5 billion years ago.
Osteon remains show up not only in the blueberries but also in
other Martian tissue fossils. The distinguishing, and unmistakable,
characteristics of the osteon remains is the clustered and overlapping
osteon-like structures with right proportion for each component in the
structures.

Meanwhile, here are some measurements to be considered when
identifying structures:
The diameter range of red blood cells: 2 microns to 25
microns(dinosaurs)
The diameter range of blood vessels: 5 microns to 10,000 microns
The diameter range of Haversian canals: 20 microns to 200
microns(dinosaurs)
The diameter range of Haversian systems (osteons): 50 microns to
500 microns.