Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published March 10, 2007 | Published
Journal Article Open

Isotopic Fractionation of Nitrogen in Ammonia in the Troposphere of Jupiter


Laboratory measurements of the photoabsorption cross section of ^(15)NH_3 at wavelengths between 140 and 220 nm are presented for the first time. Incorporating the measured photoabsorption cross sections of ^(15)NH_3 and ^(14)NH_3 into a one-dimensional photochemical diffusive model, we find that at 400 mbar, the photolytic efficiency of ^(15)NH_3 is about 38% greater than that of ^(14)NH_3. In addition, it is known that ammonia can condense in the region between 200 and 700 mbar, and the condensation tends to deplete the abundance ratio of ^(15)NH_3 and ^(14)NH_3. By matching the observed ratio of ^(15)NH_3 and ^(14)NH_3 at 400 mbar, the combined effect of photolysis and microphysics produces the ratio of (2.42 ± 0.34) × 10^(-3) in the deep atmosphere, in excellent agreement with the Galileo spacecraft measurements. The usefulness of the isotopic composition of ammonia as a tracer of chemical and dynamical processes in the troposphere of Jupiter is discussed.

Additional Information

© 2007 American Astronomical Society. Received 2006 November 11; accepted 2007 January 29; published 2007 February 21. We thank Geoff Blake and John Eiler for helpful discussion, and Andy Ackerman, Xin Guo, Run-Lie Shia, and Giovanna Tinetti for assisting the CARMA simulation, and Chris Parkinson for useful comments. Special thanks are due the referee Emmanuel Lellouch for his insightful comments. This work was supported by NASA grant NNG06GF33G to the California Institute of Technology. B.-M. C. was supported by the National Science Council of Taiwan (grant NSC95-2113-M-213-006).

Attached Files

Published - 1538-4357_657_2_L117.pdf


Files (90.5 kB)
Name Size Download all
90.5 kB Preview Download

Additional details

August 22, 2023
October 17, 2023