Earth observations show how nitrogen may be detected on exoplanets, aiding search for life

September 4, 2015 by Peter Kelley, University of Washington
The Earth as seen by the Polychromatic Imaging Camera aboard NASA’s Deep Space Climate Observatory satellite, July 2015. Credit: NASA

Observations of nitrogen in Earth's atmosphere by a NASA spacecraft 17 million miles away are giving astronomers fresh clues to how that gas might reveal itself on faraway planets, thus aiding in the search for life.

Finding and measuring nitrogen in the atmosphere of an —one outside our —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 stable on its surface. Liquid water is one of the prerequisites for life.

Should life truly exist on an exoplanet, detecting nitrogen as well as oxygen could help astronomers verify the oxygen's biological origin by ruling out certain ways oxygen can be produced abiotically, or through means other than life.

The trouble is, nitrogen is hard to spot from afar. 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 discernable spectroscopic signature.

A paper published Aug. 28 in the Astrophysical Journal by University of Washington astronomy doctoral student and lead author Edward Schwieterman, together with astronomy professor Victoria Meadows and co-authors, shows that a future large telescope could detect this unusual signature in the atmospheres of terrestrial, or rocky planets, given the right instrumentation.

The researchers used three-dimensional planet-modeling data from the UW-based Virtual Planetary Laboratory—of which Meadows is principal investigator—to simulate how the signature of nitrogen molecule collisions might appear in the Earth's atmosphere, and compared this simulated data to real observations of the Earth by NASA's unmanned Deep Impact Flyby spacecraft, launched in 2005.

The craft undertook a revised mission, called EPOXI, which included observation and characterization of the Earth as if it were an exoplanet. By comparing the real data from the EPOXI mission and the simulated data from Virtual Planetary Laboratory models, the authors were able to confirm the signatures of nitrogen collisions in our own atmosphere, and that they would be visible to a distant observer.

"One of the main messages 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," Schwieterman said. "That's why studying the Earth as an exoplanet is so important—we were able to validate that nitrogen produces 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 in hand, the researchers used a suite of Virtual Planetary Laboratory models that simulated the appearance of planets beyond the solar system bearing varying amounts of nitrogen in their atmospheres.

The detection of nitrogen will help astronomers characterize the atmospheres of potentially habitable planets and determine the likelihood of oxygen production by nonliving processes, the researchers write.

"One of the interesting results from our study is that, basically, if there's enough to detect at all, you've confirmed that the surface pressure is sufficient for liquid water, for a very wide range of surface temperatures," Schwieterman said.

Explore further: Spectrum of life: Nonphotosynthetic pigments could be biosignatures of life on other worlds

More information: "Detecting and Constraining N2 Abundances in Planetary Atmospheres Using Collisional Pairs." 2015 ApJ 810 57. DOI: 10.1088/0004-637X/810/1/57

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verkle
Sep 04, 2015
This comment has been removed by a moderator.
docile
Sep 04, 2015
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docile
Sep 04, 2015
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JustAnotherGuy
4.5 / 5 (8) Sep 04, 2015
Finding N2 is easy. Trying to relate this to the magic of spontaneous life in faraway star systems is mind-bogling.

Skipping from article's title directly to the comments section made you to omit this:
The trouble is, nitrogen is hard to spot from afar. 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.

It's on the link too:
Due to its lack of significant absorption features, N2 is extremely difficult to remotely detect.

Reading doesn't kill trolls, don't be afraid..
Steve 200mph Cruiz
4 / 5 (4) Sep 04, 2015
Docile,
Scientists get very little control. Most scientists in America work for the military, they have to do what they're told. Scientists that work in pharmacy, health care, and the chemical industry don't pick and choosewhat they work on. People that work for the state and federal government (NASA NOAA) have prioritized projects, set by congressional boards (politicians), and a limited budget that is is constantly being cut. Combined with cost overruns, they don't get to do whatever they want. Republicans think earth science is boring, so they hold up projects like the deep space climate observatory for example.

Academic scientists do have more free reign, but they still have to apply for grants and funding through other scientists and political bureaucracies, and most professional scientists aren't lucky enough to get those positions.
Torbjorn_Larsson_OM
5 / 5 (4) Sep 04, 2015
Once again, let us remind the trolls that life didn't emerge "spontaneously" but due to thermodynamic drive forces that we can phylogenetically track between life (metabolism, chemiosmosis) and geochemistry (alkaline mantle, alkaline hydrothermal vents).

But if it did emerge spontaneously, like we know the universe did when it emerged out of inflation*, what would be troublesome? At least it is a feasible physical mechanism, as opposed to the random magic 'poofs" suggested by creationists without any evidence whatsoever and based on known myths. Childish!

* Rather, it was a deterministic process with a spontaneous end according to the latest Planck data, that have the model less inflation potential as rather steep. But the moment of emergence was still spontaneous, and remind of the similar mixed processes of quantum physics and evolutionary biology.
docile
Sep 04, 2015
This comment has been removed by a moderator.
Captain Stumpy
5 / 5 (5) Sep 05, 2015
It's the scientists itself, who decide, how to spend their money - whether for research of cold fusion and/or useless search for E.T. at remote galaxies...
docile/ZEPHIR et al
1- TROLLING
2- so, you are saying that all scientists, no matter what discipline, are equivalent and up to the task of CF/LENR research?
how stupid can you get, really?
this i would expect from someone like viko or ren... maybe even from a troll like jvk... but you claim to be literate in physics and more!

you just outed yourself as one huge ignorant religious-like proselytizing DAW TROLL pushing for PSEUDOSCIENCE, man!

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