Nitrogen is one of the essential nutrients of life on Earth, with some organisms, such as the kinds of microbes found within the roots of legume plants, capable of converting nitrogen gas into molecules that other species can use.
Nitrogen fixation, as the process is called, involves breaking the powerful chemical bonds that hold nitrogen atoms in pairs in the atmosphere and using the resulting single nitrogen atoms to help create molecules such as ammonia, which is a building block of many complex organic molecules, such as proteins, DNA and RNA.
With organisms playing such a crucial role in the chemistry of nitrogen on Earth, scientists are examining nitrogen in billion-year-old rocks to decipher its potential as a bio-signature of life on other planets. New findings in this area of research appeared recently in the paper, "Nitrogen in Ancient Mud: A Biosignature?" in the journal Astrobiology.
"This study identifies nitrogen abundances as a potential tool to detect remnants of life on Mars," said one of the study's authors, Eva Stüeken, an astrobiologist at the University of Washington at Seattle and the University of California at Riverside.
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The presence of large quantities of oxygen ions may be able to distinguish habitable exoplanets with life from barren exoplanets in the habitable zone (resembling Venus or Mars):
Like Earth, Venus and Mars are small rocky planets; they have permanent atmospheres like Earth, and their atmospheres are exposed to the same solar radiation as Earth's. Data from the Pioneer Venus Orbiter and the Viking descent probe on Mars show that they have very similar ionospheres to each other—which don't contain a lot of atomic O+ ions. Know what else Venus and Mars are missing? Photosynthesis.
[Astronomy PhD candidate Paul] Dalba's contention is that photosynthesis on a planet's surface, which generates a surfeit of molecular oxygen, is the only thing that can account for these atomic O+ ions in a planet's ionosphere. The mere existence of life throws a planet's atmosphere out of chemical balance. O+ would be a neat biomarker because there isn't a numerical cutoff required—just the dominance of O+ among the ionic species in the upper atmosphere would indicate "thriving global biological activity" on the planet below.
Dalba claims that Venus and Mars act as negative controls, demonstrating that planets like Earth but lacking life don't have this O+ layer. Some may think that continuous volcanic activity on the surface could also generate enough oxygen, but Dalba doesn't. Chemistry involving water and UV light [open, DOI: 10.1038/srep13977] [DX] can also release oxygen. But the amount of water on Earth is insufficient to account for the requisite oxygen content, so he thinks that the presence of water on other planets wouldn't make enough oxygen there either.
Atomic oxygen ions as ionospheric biomarkers on exoplanets (DOI: 10.1038/s41550-017-0375-y) (DX)
Related: Nitrogen in Ancient Rocks a Sign of Early Life
Oxygen Ions From Earth Escape to the Moon
Researchers Suffocate Hopes of Life Support in Red Dwarf "Habitable Zones"
Seven Earth-Sized Exoplanets, Including Three Potentially Habitable, Identified Around TRAPPIST-1
Cosmic Methyl Chloride Detection Complicates the Search for Life on Exoplanets
Mars Colonists Could Produce Oxygen by Making a Plasma Out of Atmospheric Carbon Dioxide
Analysis of Microfossils Finds that Microbial Life Existed at Least 3.5 Billion Years Ago
To Detect Life on Other Planets, Look for Methane, Carbon Dioxide, and an Absence of Carbon Monoxide
(Score: 1, Interesting) by Anonymous Coward on Thursday December 01 2016, @04:17AM
Isn't it great how strigoi spray ammonia while they feed. Their digestive tract is so elegant that liquid simply goes in one end and out the other simultaneously. Blood in the stinger, ammonia out the cloaca. The biological complexity of human cattle is vulgar by comparison. It's no wonder the human cattle are prone to disease and death.
(Score: 2) by linkdude64 on Thursday December 01 2016, @02:55PM
Can't wait until this new technique works its way into Ancient Aliens.
"Chemical analysis inside the pyramids of Egypt suggest that living creatures had farted here millions of years before the pyramids were said to be built. Coincidence? You decide."