LOS ANGELES - NASA's Phoenix spacecraft has detected the presence of a chemically reactive salt in the soil of Mars.
If the finding is confirmed, it could make the red planet less friendly to potential life than once believed.
Scientists previously reported that the soil near Mars' north pole was similar to backyard gardens on Earth where plants such as asparagus, green beans and turnips could grow.
But preliminary results from a second lab test found perchlorate, a highly oxidizing salt, that would create a harsh environment.
On Earth, perchlorate is a natural and manmade contaminant sometimes found in soil and groundwater.
It is the main ingredient in solid rocket fuel and can be found in fireworks, pyrotechnics and other explosives.
It's unclear how perchlorate forms on Mars or how much there is of it.
NASA is investigating whether the substance could have gotten there by contamination before launch.
Phoenix used another fuel, hydrazine, to power its thrusters and land on Mars on May 25th.
