Just after the Mars rover Curiosity completed its first scoop of Martian soil, project leaders halted the testing process when a small piece of unknown junk was found in one of the pictures.

It turns out the refuse is harmless, and NASA’s Jet Propulsion Laboratory this week resumed the soil testing process, which involved vibrating the sample “vigorously” to clean the surfaces of Curiosity’s sample-processing chambers. NASA stated that the bright object found on the ground is thought to be a type of plastic wrapping material that could possibly have fallen onto Curiosity during the Mars Science Laboratory’s descent toward Mars.

Meanwhile, researchers on Earth have analyzed the data obtained by the rover last month when it stopped to examine a football-sized rock named Jake Matijevic. It was the first rock that Curiosity analyzed using its Alpha Particle X-Ray Spectrometer (APXS). The results, which revealed the chemical composition of the rock, were surprising to the rover team.

“This rock is a close match in chemical composition to an unusual but well-known type of igneous rock found in many volcanic provinces on Earth,” said Edward Stolper, a geologist at the California Institute of Technology. “With only one Martian rock of this type, it is difficult to know whether the same processes were involved, but it is a reasonable place to start thinking about its origin.”

NASA stated that similar rocks on Earth are formed beneath the planet’s crust, in the mantle. They form from “crystallization of relatively water-rich magma at elevated pressure.”

“Jake is kind of an odd Martian rock,” said Ralf Gellert, APXS principal investigator and assistant professor at the University of Guelph. “It’s high in elements consistent with the mineral feldspar, and low in magnesium and iron.”

(Image courtesy NASA/JPL-Caltech/MSSS)