"We thought, what can the rock do for you?" Scott says. "You don't want to damage the sample more than you have to. You'd like to just shoot it directly."
With funding from NASA's Astrobiology program, the researchers have done previous studies showing that minerals like halite and jarosite yield distinct ion patterns when organic molecules are present. This time, they tried thenardite, a compound thought to be part of the Martian surface. Because thenardite is left behind when lakes dry up, its presence could signify the past existence of water -- and hence life.
The team tested thenardite samples taken from the evaporated Searles Lake bed in California. They also created artificial thenardite samples that contained traces of stearic acid, which is left behind by dead cells, and glycine, the simplest amino acid used by organisms on Earth. In all cases, the researchers found a distinct ion pattern that did not appear for thenardite alone, suggesting they had detected a signature for the biomolecules.
The team also measured the sensitivity of its instrument for the first time. By testing more and more dilute artificial samples, they found they could detect the stearic acid signature at levels as low as 3 parts per trillion. In fact, the signatures became even more distinct as concentration dropped, presumably because more ion-producing matrix surrounded each biomolecule.
While the instrument is too big to send into space, it could potentially be used for analysis if NASA brings Martian samples back to Earth. The INL study also could help determine which samples should be collected, based on how likely they are to show signs of life. Thenardite and jarosite look the most promising, Scott says, while hematite -- an iron-based compound common on the Martian surface -- has yielded poor results so far.
|Contact: Roberta Kwok|
DOE/Idaho National Laboratory