No Martians, but NASA's Curiosity rover reports that the first soil sample taken from Mars contains chlorine-laced compounds similar to ones seen on the Red Planet's frozen poles and tantalising hints of others that could be precursors to life's chemistry.
NASA landed the $US2.5 billion rover on Mars in August on a mission to search for signs of chemistry indicating whether habitable conditions for life once existed, or still exist, there.
The soil sample results reported at the American Geophysical Union meeting in San Francisco contain hints of "organic" chemicals essential to biochemistry, but the rover team said more analysis is needed.
"We just don't know if these are indigenous to Mars, and it is going to take some time to work through," said mission chief scientist John Grotzinger of Caltech.
The carbon compounds could be earthly contamination from the sampling instruments. Determining whether these compounds represent "some kind of biological material is well down the road for us," he added.
A sand pit called Rocknest served up the first soil sample, its dirt largely made of iron minerals typical of the fine Martian dust coating the Red Planet. "It's finer than sugar, but coarser than flour," said mission imaging scientist Ken Edgett of Malin Space Systems in San Diego.
The data shows that Martian soil is a complex makeup of water, sulfur and chlorine-containing substances. The samples’ composition is about half common volcanic minerals and half non-crystalline materials such as glass.
Speculation of dramatic chemistry results that preceded Monday's presentation led NASA's Jet Propulsion Laboratory, which manages the rover, to issue a news release in advance, downplaying the results.
Since arriving in August, the nuclear-powered rover has travelled nearly 1700 feet from its landing site inside the 154-kilometre-wide Gale Crater on Mars. Within a year, the rover will travel to apparent clay formations ringing Aeolis Mons, or "Mount Sharp," a mountain that rises 5.5 kilometres above the floor of the crater. The rover is now stationed near a rock it will inspect with a drill this week, another first for a Mars rover.