Nasa lander finds potentially toxic substance on Mars

Los Angeles: The Phoenix Mars Lander may have detected perchlorate, a potentially toxic substance, in soil samples taken from Mars, Nasa scientists said on Monday.

Nasa said further tests were required to confirm the presence of perchlorate in Mars and to rule out the possibility that perchlorate could have been brought there by Phoenix.

Last week, Nasa said Phoenix had provided definitive proof that water exists on Mars after further tests on ice found by the lander in June.

Perchlorate, an oxidizing substance, is known to be harmful to humans under certain circumstances.

Its existence in the soil could suggest that Mars is less hospitable to life than the scientists have so far believed.

"This is surprising since an earlier measurement of surface materials was consistent with but not conclusive of the presence of perchlorate," said chief investigator Peter Smith.

Phoenix touched down in May on an ice sheet and samples of the ice were seen melting in photographs taken by the lander's instruments in June.