Mars rover Curiosity took these images of the “Darwin” site (note 1) on Mars on Sol 390 & Sol 392:
SIX RED RECTANGLES MARK REMNANTS OF CONCRETE PAVEMENTS CONSTRUCTED BY ADVANCED MARTIANS. ALL OVER MARS ARE NUMEROUS SUCH CONCRETE PAVEMENT REMAINS. IMAGE CREDIT: HORTONHEARDAWHO. See also: http://www.gigapan.com/gigapans/140117 ( See the white-balanced image at right.)
If “Darwin” on Mars Is Not Concrete, What Is Concrete?
Added on Sept. 17, 2013: California Highway Remains Resemble Martian “Darwin”:
“Remains of the old historic Coast Highway 101 in California”. GREEN ARROWS AND RED RECTANGLES MARK CONCRETE PAVEMENT REMAINS RESEMBLING THOSE AT ''DARWIN” SITE ON MARS.
Added on Sept. 18, 2013: Apparent Concrete Pavement/Blocks at Darwin, Mars–
RED LINES MARK REMNANTS OF CONCRETE PAVEMENTS AND CONCRETE BLOCKS CONSTRUCTED BY ADVANCED MARTIANS. CURIOSITY SOL 395 IMAGES. FEW BIG OBJECTS HERE HAVE THE SHAPES OF COMMON ROCKS.
Added on Sept. 19: You don’t need an education to recognize these concretes:
“Adding more images to the (CURIOSITY) Mastcam100 Sol-395 Panorama.” RED AND GREEN RECTANGLES MARK REMNANTS OF CONCRETE PAVEMENTS AND CONCRETE BLOCKS, RESPECTIVELY. FEW BIG OBJECTS HERE HAVE THE SHAPES OF COMMON ROCKS.
Added on Sept. 22, 2013: Photos of concrete on Earth for comparison–
Broken concrete pieces on Earth:
RED CIRCLES MARK BROKEN CONCRETE PIECES THAT LOOK LIKE THOSE FOUND ON MARS. IMAGED ON THE EARTH.SOURCE OF IMAGE: http://es.123rf.com/photo_17099947_rotos-pedazos-de-concreto-como-fondo-o-textura.html
Surface texture of normal concrete on Earth showing gravel and cement (note: Its magnification is higher than Martian panoramas):
CLICK ON PHOTO TO SEE PEBBLES IN CEMENT. SOURCE OF PHOTO: http://www.andrewkelsall.com/royalty-free-images-cement-pebbles/
Surface texture of degraded concrete on Earth:
FIGURE SHOWS “Concrete surfaces with different depths of erosion”. RED RECTANGLE SHOWS SURFACE (DEPTH = 0 mm) OF DEGRADED (ERODED) CONCRETE. THERE ARE OTHER KINDS OF CONCRETE SURFACES. IMAGE SOURCE: http://www.cement.org/tech/cct_dur_acid.asp
Other kinds of eroded surfaces of concrete on Earth:
THERE ARE MANY KINDS OF TEXTURES ON WEATHERED CONCRETE. WEATHERED CONCRETE SURFACE MAY BE CONTAMINATED WITH CELLULAR FOSSILS, CORALS, ETC. IMAGE SOURCE: http://www.sciencedirect.com/science/article/pii/S0167844298000627