Nitrogen in Ancient Rocks Could Detect Signs of Early Alien Life on Mars
Scientists are examining the potential of nitrogen in ancient rocks to detect life on other planets, Mars in particular.
Nitrogen is one of the essential nutrients of life on Earth. Some organisms are capable of breaking down chemical bonds in nitrogen gas into molecules that other organisms can use.
According to Astrobiology Magazine, the process, which is called nitrogen fixation, involves breaking down powerful chemical bonds that hold paired nitrogen atoms in the atmosphere and using the single nitrogen atoms to create molecules (such as ammonia) that serve as a building block of many complex organic molecules, which includes proteins, DNA and RNA.
Based on its role in the Earth's chemistry, Eva Stüeken, an astrobiologist at the University of Washington in Seattle, is determining if nitrogen in 3.8 billion-year-old rocks from the Isua Supracrustal Belt in Greenland could be bio-signatures of life on Mars. The study was recently published in the journal Astrobiology.
Previous research interpreted that organic carbon molecules in these ancient rocks are biogenic -- the results of which had been controversial since the widely accepted date for earliest life has been only 3.5 billion years.
"It is possible to make organic carbon even in the absence of life," Stüeken said. "So those studies have been viewed with skepticism by some researchers, and an independent biosignature was needed."
Stüeken focused on relatively high nitrogen levels found in mineral biotite in the Isua rocks, the nitrogen concentrations of which are similar to what could be found in modern mud, and determined if the amount of nitrogen could result from abiotic sources.
According to Stüeken, abiotic processes may have been much more important to nitrogen fixation than biological ones. She developed a model of abiotic nitrogen processes that could have played a role in early Earth and found that such abiotic processes alone could not explain the nitrogen levels contained in the Isua rocks.
"The results provide more evidence of an early origin of life on Earth -- before 3.8 billion years ago," Stüeken said, adding that nitrogen abundances could be a useful tool in for upcoming Mars missions.