NASA's plucky Mars rover Opportunity has discovered what appears to be another meteorite on the surface of the Red Planet, bringing its lifetime total to five so far.

The rover spotted the rock at the end of its 81-meter (266-foot) drive on Sept. 16, NASA officials said. It appears as a dark, toaster-sized rock in photos taken by the rover from 31 meters (102 feet) away. [Photo: Rover's latest Mars meteorite.]

"The dark color, rounded texture and the way it is perched on the surface all make it look like an iron meteorite," said rover science team member Matt Golombek of NASA's Jet Propulsion Laboratory in Pasadena, Calif.

The newfound rock has been given the informal name "Oilean Ruaidh" (pronounced ay-lan ruah), which is the Gaelic name for an island off the coast of northwestern Ireland. The rock appears to be about 45 centimeters (18 inches) wide.

Rover mission managers plan to send Opportunity in to get a closer look at the rock to determine it is indeed a meteorite, NASA officials said.

If so, it would be the fifth iron meteorite the rover has found since it began exploring Mars' Meridiani Planum region in 2004.

Examination of these rocks has yielded information about the Martian atmosphere, as well as the meteorites themselves, rover scientists said.

Opportunity has now driven 14.5 miles (23.3 km) on Mars, according to NASA officials. The drive to the possible meteorite will take the total combined distance driven by Opportunity and its twin, Spirit, to more than 19.26 miles (31 km).

Opportunity and Spirit both landed on Mars in January 2004. Their mission was initially slated to last only about three months, but both far surpassed that lifetime.

Last year, Spirit got bogged down in soft sand and stopped communicating with Earth in spring of this year. Opportunity, though, is still going strong and headed to a huge crater called Endeavour.