The mystery of where amino acids found in lunar soil samples from the Apollo missions has stumped scientists for decades. They certainly didn't come from the moon, which is completely inhospitable to life. But with help from the Goddard Astrobiology Analytical Laboratory, NASA researchers have finally tracked down the source of the contamination.
"People knew amino acids were in the lunar samples, but they didn't know where they came from," Jamie Elsila of NASA's Goddard Space Flight Center, said in a statement. "The scientists in the 1970s knew the right questions to ask and they tried pretty hard to answer them, but they were limited by the analytical capabilities of the time. We have the technology now, and we've determined that most of the amino acids came from terrestrial contamination, with perhaps a small contribution from meteorite impacts."
Figuring that out, however, was not nearly as cut and dry as it sounds. NASA initially identified four potential sources for the contamination: the astronauts themselves; the lunar module's exhaust fumes, which contain organic compounds; solar winds that could have deposited elemental precursors like carbon and nitrogen onto the moon's surface; or meteorites which could have delivered the molecules from a far-flung corner of the galaxy.
By first determining the relative levels of isotopes, specifically Carbon-13, the researchers were able to eliminate solar winds as the primary contributor since they carry very little Carbon-13. They next eliminated lunar module exhaust gas as the culprit since samples taken from directly under the module had the same levels of amino acids as samples taken more than four miles away. If exhaust gas were to blame, acid levels would have been much higher in the first sample. Finally, they looked at the orientation of the amino acids -- that is, whether they "lean" left or right, like your hands. Organic amino acids are almost exclusively of the left variety and non-biological amino acids tend to appear as both left and right in equal proportions. The acids that NASA studied were almost all left sided, which means they most likely came from Earth.
That doesn't entirely rule out meteorites as a source, especially since researchers found a number of acids that are common in meteorites but rare on Earth, but the analysis strongly suggests that most of the contamination came from here. NASA researchers hope to use this as a teaching moment and apply what they've learned to future surveys.
[Image Credit: Getty]