The first chemistry results from Mars' northern plain reveal an environment more hospitable to life than some scientists had predicted, one that might allow future colonists to grow crops as familiar on Earth as asparagus and green beans.
Strawberries, though, might be tougher, Phoenix mission scientists said Thursday.
"We're flabbergasted by this data," said Sam Kounaves, the lead scientist for the wet chemistry experiment on the Phoenix spacecraft, which landed May 25 on Mars. "We've found nutrients that could support life."
A sample of soil about the size of a sugar cube was delivered to the lab by the lander's nearly 8-foot-long robotic arm and mixed with water brought from Earth.
Analysis showed that the soil is alkaline, with a pH between 8 and 9, Kounaves said. This was a surprise to the many scientists who had argued that Martian soil was probably too acidic to support life.
With that level of alkalinity, "you might be able to grow asparagus very well," Kounaves said. Strawberries, on the other hand, require more acidic soil.
The test also turned up magnesium, sodium, potassium and chloride, all of which are useful in organic processes.
The test did not turn up the prize that the $420-million mission was sent to find: complex organics indicating that the cold, dry planet once was, or still might be, habitable.
Organic compounds, made up of carbon in combination with nitrogen, hydrogen and other elements, are necessary to build the elaborate chemical scaffolding of life, at least as we know it on Earth.
Furthermore, even though the soil chemistry would provide some nutrients for life, any future crops would have to be grown underground, because the meager atmosphere lets in too much of the sun's destructive ultraviolet rays.
The scientific team from the University of Arizona and the Jet Propulsion Laboratory in La Canada Flintridge emphasized that these results represent an analysis of a single piece of the Martian landscape.
"A lot of people predicted the soil would be acidic," Kounaves added. "We're showing at this location it appears to be alkaline. But we're only looking at a tiny area."
Still, the scientists said Thursday in a briefing, these early results are encouraging.
"There's nothing about [the soil] that would preclude life," Kounaves said. "Some types of life would be happy to live in these soils."
In fact, the Martian soil looks very similar to soil on Earth, only without the organics, he said.
Fuller answers to the habitability question are expected from Phoenix's other major laboratory, the thermal and evolved-gas analyzer, which contains eight tiny ovens to "bake and sniff" the soil, as well as the ice lying inches beneath the lander.
Scientists said they had received the results of heating the first soil sample up to 1,800 degrees Fahrenheit. Small amounts of carbon dioxide and water were released, according to William Boynton, the lead scientist for the analyzer.
Neither finding was surprising. The Martian atmosphere is mostly made up of carbon dioxide. NASA's twin rovers, Spirit and Opportunity, that have been rolling around the planet's equatorial regions since 2004 found evidence of ancient pools or seas of standing water.
Sometime in the next few weeks of the three-month mission, the scientific team will attempt to bore into the hard-as-cement ice layer. After breaking off shards of ice, the robotic arm will try to inject them into the spacecraft's ovens.