Back in the 1970s, scientists analyzed samples brought back from the moon and identified some of the material as including amino acids. The problem: Where did they come from?
Yes, the samples themselves were collected from the moon during NASA's Apollo missions. But scientists didn't believe the amino acids, which are used to build proteins in living things, actually originated on the moon, as it was inhospitable to known life forms.
Thus, their origins had four options, according to NASA.
1) Contamination: The amino acids were brought to the moon by humans in missions or were introduced when the samples were back on Earth.
2) Rocket exhaust: Rocket exhaust has molecules that can build amino acids.
3) Solar wind: The gas being blown from the surface of the sun also has elements that can make amino acids.
4) Asteroids: Asteroids have been known to contribute "extraterrestrial amino acids" to Earth when they fall through the atmosphere as meteorites. The lunar surface gets its marked surface from such meteorite collisions.
"People knew amino acids were in the lunar samples, but they didn't know where they came from," Jamie Elsila with NASA's Goddard Space Flight Center in Maryland 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."
NASA scientists recently analyzed seven samples from the moon taken during the Apollo missions. Conducting isotopic analysis with instrumentation at the Goddard Astrobiology Analytical Laboratory, the team was able to determine that terrestrial contamination from Earth "with perhaps a small contribution from meteorite impacts" were the source of the amino acids, Elsila said.
"This work highlights the fact that even with thoughtful and careful contamination control efforts, trace organics in extraterrestrial samples can be overwhelmed by terrestrial sources," Elsila said. "Future missions emphasizing organic analysis must consider not only contamination control but also include 'witness samples' that record the environment and potential contamination as the mission is built and launched to understand the unavoidable contamination background."
The issue of terrestrial contamination was something that came up in a recent NASA news conference regarding its missions to Mars as scientists continue the search for the possibility of life on the red planet.
In September NASA announced the presence of flowing water under certain conditions on Mars. With water, so comes the possibility for life to exist.
“We're being very careful that we don’t send a spacecraft to Mars with the intention of detecting Martian life—and find out that we detected the Earth life that we took with us,” John Grunsfeld, associate administrator for the Science Mission Directorate at NASA, said at the news conference in September regarding the issue of contamination, the Atlantic reported. “That’s tough to do.”