(Reuters) - NASA's Mars rover Curiosity tasted Martian dirt for the first time on Thursday, testing equipment needed to assess if the planet most like Earth in the solar system has or ever had the ingredients for microbial life.

The sampling of about a baby aspirin's worth of Martian sand was slightly delayed while scientists puzzled over unusual brightly colored flecks in the hole carved out by Curiosity's scoop.

Initially, the team believed the bright flecks were shed by the rover, similar to bits of plastic debris discovered last week.

"The science team started to classify these sort of differently, calling them 'schmutz,'" Curiosity lead scientist John Grotzinger, with the California Institute of Technology, told reporters in a conference call.

"We had a lot of fun with that, labeling them and comparing, but in the end it turns out we really feel this is a different sort of particle," he said.

While not completely ruling out the chance that the flecks are rover debris, most of the team now believes they are naturally occurring, perhaps a mineral that was fractured by the rover scoop.

To be on the safe side, scientists commanded Curiosity to dump that sample and collect sand from another site for processing in the onboard laboratory. The aim is to get an ingredient list of minerals in the Martian soil.

"We got to believing there were things around us and began to look at everything through that lens," said mission manager Richard Cook, with NASA's Jet Propulsion Laboratory in Pasadena, California.

"We definitely are more aware of what's out there now and are more careful about everything we look at," Cook said.

In August, Curiosity landed inside a 96-mile-wide (154-km-wide) impact crater near the Martian equator on a $2.5 billion, two-year mission to determine if Mars had the chemistry to support and preserve microbial life.

The mission is NASA's first astrobiology initiative since the 1970s-era Viking probes.