A fossilized limb, complete with muscle and bone, was found on Mars by
Mars rover Spirit on sol 1863 and sol 1866.
Martian limb location: http://www.wretch.cc/album/show.php?...555415619&p=41

Limb/muscle/bone cross sections:
http://www.wretch.cc/album/show.php?...555459780&p=43

Muscle fascicles:
http://www.wretch.cc/album/show.php?...555459779&p=44

Muscle cells:
http://www.wretch.cc/album/show.php?...555500282&p=50

Osteon canals in bone:
http://www.wretch.cc/album/show.php?...555513826&p=52

Sources of above images:
http://www.flickr.com/photos/hortonh...ho/3455362413/

http://marsrovers.nasa.gov/gallery/a...P2555L5M1.HTML

http://marsrovers.nasa.gov/gallery/a...P2956M2M1.HTML

Earthly human leg transverse section for comparison:
http://www.wretch.cc/album/show.php?...555429388&p=42

http://www.wretch.cc/album/show.php?...555466320&p=45

http://www.wretch.cc/album/show.php?...555466319&p=46