It's almost time for NASA's Curiosity rover to make contact with a Martian—a Martian rock, that is.

The rover, now six weeks into its mission on the Red Planet, is preparing to place its Alpha Particle X-Ray Spectrometer (APXS) against a rock to analyze its composition. Powered by 0.7 milligram of radioactive curium 244, APXS irradiates samples with alpha particles (nuclei of helium atoms) and x-rays to make sensitive measurements of chemical makeup.

"We're now at a point where we want to start to do some surface-contact science," mission project manager Richard Cook of the NASA Jet Propulsion Laboratory in Pasadena, Calif., said during a September 19 teleconference.

Curiosity is headed toward a geologic site called Glenelg, where multiple terrain types meet. Along the way, mission personnel spotted the rock pictured above and deemed it a worthy first target. Project scientist John Grotzinger said the rock looked to have a uniform composition, which will allow Curiosity to check its measurements from APXS against those from the rover's ChemCam instrument, which has a smaller field of view. "The hope is that we can analyze this rock and do some cross-comparisons between the two instruments," Grotzinger said. "Not to mention it's just a cool-looking rock."

The target rock has been named Jake Matijevic for a member of the rover team who died in August, just two weeks after landing, following "a lifelong battle with asthma and other upper respiratory ailments," according to an obituary in the Chicago Tribune.

—John Matson