Discovery about rare nitrogen molecules offers clues to makeup of other life-supporting planets | UCLA
http://newsroom.ucla.edu/...trogen-molecules-offers-clues-to-makeup-of-other-life-supporting-planets
team of scientists using a state-of-the-art UCLA instrument reports the discovery of a planetary-scale “tug-of-war” of life,
deep Earth and the upper atmosphere that is expressed in atmospheric nitrogen.
The Earth’s atmosphere differs from the atmospheres of most other rocky planets and moons in our solar system in that it is rich
in nitrogen gas, or N2; the Earth’s atmosphere is 78 percent nitrogen gas. Titan, the largest of Saturn’s more than 60 moons, is
the other body in our solar system with a nitrogen-rich atmosphere that resembles ours.
Compared with other key elements of life — such as oxygen, hydrogen and carbon — molecular nitrogen is very stable. Two nitrogen
atoms combine to form N2 molecules that stay in the atmosphere for millions of years.
The majority of nitrogen has an atomic mass of 14. Less than one percent of nitrogen has an extra neutron. While this heavy isotope,
nitrogen-15, is rare, N2 molecules that contain two nitrogen-15s — which chemists call 15N15N — are the rarest of all N2 molecules.
The team of scientists measured the amount of 15N15N in air and discovered that this rare form of nitrogen gas is far more abundant
than scientists had expected. The Earth’s atmosphere contains about two percent more 15N15N than can be accounted for by geochemical
processes occurring near the Earth’s surface.
“This excess was not known before because nobody could measure it,” said senior author Edward Young, a UCLA professor of geochemistry
and cosmochemistry. “Our one-of-a-kind Panorama mass spectrometer allows us to see this for the first time. We conducted experiments
showing that the only way for this excess of 15N15N to occur is by rare reactions in the upper atmosphere. Two percent is a huge excess.”
Young said the enrichment of 15N15N in Earth’s atmosphere is a signature that’s unique to our planet. “But it also gives us a clue about
what signatures of other planets might look like, especially if they are capable of supporting life as we know it.”