Scientists operating the Phoenix spacecraft say the Martian soil near the north pole landing site is similar to what can be found in the Chile desert on Earth.
The lander recently detected an ingredient of rocket fuel in soil samples taken from the surface of the red planet.
Scientists said the chemical - perchlorate - is found naturally in Chile's Atacama Desert, where extreme microbes live. They say its presence on Mars is neither good nor bad for potential life.
NASA is trying to rule out the possibility that the chemical may have gotten there through contamination.