June 24 (UPI) -- NASA's Martian rover Curiosity has discovered elevated methane levels on the Red Planet.
The rover's Sample Analysis at Mars tunable laser spectrometer, or SAM instrument, measured approximately 21 parts per billion units by volume of methane in the Martian atmosphere -- the largest single reading since Curiosity's scientific mission began.
As of now, Curiosity and NASA scientists working on the Curiosity mission can't determine the methane's source. Researchers are also unable discern whether the methane source is local or distant. Curiosity is currently exploring Gale Crater.
"With our current measurements, we have no way of telling if the methane source is biology or geology, or even ancient or modern," Paul Mahaffy, scientist at NASA's Goddard Spaceflight Center and principle investigator for the rover's SAM instrument, said in a news release.
Both Curiosity and ESA's Mars Express probe have previously measured methane spikes on Mars. Earlier this year, scientists analyzing methane measurements made by the two spacecraft determined the seasonal methane spikes are most likely explained by small, transient geological events.
Scientists concluded a frozen slab of ice or permafrost containing methane, located beneath tectonic faults outside of Gale Crater, is the most logical explanation for the Red Planet's seasonal methane spikes. The research team estimated periodic melting causes the ice to release the compound in gas form.
NASA scientists have developed a test for the rover to conduct over the coming weekend to determine whether the most recent record-breaking methane measurement was caused by a transient methane plume.