And it depends on the bias that you place on the information.

From the web site:
http://cosmiclog.nbcnews.com/_news/2012/12/03/15645732-curiosity-rover-finds-organic-compounds-but-are-they-from-mars?lite

“he said it wasn't yet clear whether the tiny amount of carbon in the compounds came from the Martian soil or was actually brought to Mars from Earth by Curiosity itself.”

Also from the same source: “Perchlorate, which was also found by NASA's Phoenix Mars Lander in 2008, is considered a toxic substance and used as an ingredient in rocket fuel on Earth. But scientists say the compound could conceivably serve as an energy source for hardy microbes on Mars.”

The first one of the above comments seems kind of curious to me, for one thing I’d like to know how much carbon do these spacecraft carry from Earth to Mars.
I have been under the impression that carbon is a mineral element that is found everywhere in the universe, why would Mars be excluded from containing the carbon element? After all, even the atmosphere is mostly carbon dioxide.

Mars Fact Sheet

http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html