Scientists at the U.S. space agency, NASA, say the Mars Phoenix lander has found a toxic chemical on the surface of the planet.
The scientists said Tuesday that soil samples scooped up by the lander contained perchlorate, a chemically reactive salt.
NASA researchers say they are carrying out further tests to determine if the soil is representative of a wider area of Mars. They also are investigating whether the lander could have brought the chemical to the Martian surface.
Perchlorate is used on Earth in rocket fuel. Scientists say finding the chemical in Martian soil does not rule out the possibility that life once existed on Mars or could exist now. They say the chemical is harmless to most organisms.
Last week, NASA said it had definitive proof that water exists on Mars after conducting tests on ice found by the lander in June.
Perchlorate is found on Earth in extremely dry climates, including the Atacama Desert in Chile, where the soil has been described as Mars-like.
Some information for this report was provided by Reuters.