Scientists: Salt in Mars soil is not bad for life

Traces of a rocket fuel ingredient found in the Martian soil would not necessarily hinder potential life, mission scientists said on Tuesday.

NASA's Phoenix spacecraft earlier this summer detected the chemical perchlorate, a highly oxidizing salt, in soil samples dug up from near the Martian surface. On Earth, it can be found naturally in the arid Atacama Desert in Chile where some extreme organisms use it as a source of energy.

"We know that microbes can exist quite happily in oxidizing conditions," said Phoenix scientist Richard Quinn of the NASA Ames Research Center. "The story possibly could turn out to be the same for Mars. We don't know yet."

The surprising find comes after scientists previously reported that the soil near Mars' north pole was Earth-like where plants such as asparagus, green beans and turnips could thrive. The presence of perchlorate, if confirmed, would appear to make the soil more exotic than previously believed.

But scientists insisted that has no bearing on the red planet's habitability.

"In itself, it is neither good nor bad for life," chief scientist Peter Smith of the University of Arizona in Tucson said of the chemical.

Some researchers who have no role in the $420 million mission were less enthusiastic.

"Perchlorate is not a particularly nice thing to find in the soil," said astrobiologist Kenneth Nealson of the University of Southern California. "No one hunting for life would be happy to see it in any sort of abundance."

Although some microbes on Earth thrive on perchlorate, "it is not a molecule of choice for most life," Nealson said.

Phoenix landed in the Martian arctic plains on May 25 to study whether the region could support life, past or present. It confirmed the presence of ice at the landing site, but it has yet to uncover organic, or carbon-based, building blocks of life.

The spacecraft detected perchlorate in two soil samples taken from different shallow trenches in June and July using its onboard chemistry lab. Scientists are working to confirm the signal because another Phoenix instrument, also capable of sniffing out the chemical, failed to turn up any evidence in a test last week.

Agencies

(China Daily 08/07/2008 page38)