Life on Alien Planets: Earth Reveals How to Detect Nitrogen on Exoplanets

There may be a new tool to detect life on alien planets. Scientists have received fresh clues as to how nitrogen could be used to detect life on other planets.

Finding and measuring nitrogen in the atmosphere of an exoplanet can be crucial to determining if that world might be habitable. That's because nitrogen can provide clues to surface pressure. If nitrogen is found to be abundant in a planet's atmosphere, that world almost certainly has the right pressure to keep liquid water stable on its surface.

However, nitrogen is hard to spot from far away. In fact, it's often called an "invisible gas" because it has few light-altering features in visible or infrared light that would make it easy to detect. The best way to detect nitrogen in a distant atmosphere is to measure nitrogen molecules colliding with each other. The resulting instantaneously brief "collisional pairs" create a unique and discernible spectroscopic signature.

Now researchers have found that a future large telescope could potentially detect this unusual signature in the atmospheres of terrestrial planets, given the right instruments.

The scientists used three-dimensional planet-modeling data in order to simulate how the signature of nitrogen molecule collisions might appear in Earth's atmosphere and then compared this simulated data to real observations of Earth by NASA's unmanned Deep Impact Flyby Spacecraft.

"One of the main message of the Virtual Planetary Laboratory is that you always need validation of an idea-a proof of concept-before you can extrapolate your knowledge to studying a potentially Earth-like exoplanet," said Edward Schwieterman, one of the researchers, in a news release. "That's why studying Earth as an exoplanet is so important-we were able to validate that nitrogen procures an impact on the spectrum of our own planet as seen by a distant spacecraft. This tells us it's something worth looking for elsewhere."

This confirmation should help researchers potentially detect nitrogen on other planets. This, in turn, could be huge in terms of learning a bit more about other exoplanets.

The findings are published in The Astrophysical Journal.

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