This is the first of two guest posts from Tim Cullen on the fascinating subject of photon production in planetary atmospheres:
The concept of a “fluorescing atmosphere” is generally dismissed as cranky [or just plain crazy] by most pundits and commentators.
Therefore, I am extremely grateful to Professor Mark A. Smith and Hiroshi Imanaka for publishing a truly remarkable paper on the Geochemical Society website that clearly illustrates that photons are produced in the atmosphere.
The blue emissions are indicative of atomic hydrogen [but there are other atmospheric atomic gases that emit blue photon – such as helium] and are produced in many ways [including]:
a) Electrons colliding with atomic gas particles.
b) Solar photon colliding with atomic gas particles.
c) Atomic gas particles recombining to form molecules.
Using the Ion-Neutral Mass Spectrometer (INMS) on Cassini, we now know that even in the ionosphere, there is a rich and complex organic chemistry unparalleled in any known atmosphere (Waite, 2005; Waite, 2009).
Using the Cassini Plasma Spectrometer (CAPS) originally designed to measure properties of the small ions and free electrons in the magnetosphere of Saturn, it has discovered that at the highest altitudes of the Titan atmosphere there exist surprising concentrations of very large charged particles, now believed to be the chemical seeds of the Titan haze (Coates 2007).
Chemistry at these levels is driven by the solar extreme ultraviolet radiation (EUV) below 150 nanometers (nm) as well as the more minor energetic electrons entering the atmosphere guided by the strong saturnian magnetic field, as depicted graphically in Figure 2.
The dissociation and ionization of nitrogen and methane leads to a reforming plasma which is now known to produce benzene, formimine and other complex molecules at regions of the atmosphere where on Earth only small atoms, ions and diatomics exist (Imanaka, 2007; Imanaka, 2009).
The predominant difference being Titan’s currently reducing methane rich atmosphere, a condition thought to be relevant however during the prebiotic stages of Early Earth. In fact, when one factors in the 100 times lower solar energy flux received by Titan relative to Earth, the resulting lower atmospheric and surface temperatures, and the positive activation energies of much of the complex neutral chemistry required to generate a prebiological chemistry, one can argue that Titan is geochemically reminiscent of Early Earth in its organic chemistry.
Complex Organic Carbon on Abiotic Solar System Bodies: Titan as a model
Mark A. Smith, Hiroshi Imanakaa,
Department of Chemistry and Biochemistry, University of Arizona, Tucson
Department of Planetary Science, University of Arizona, Tucson
Mark A. Smith is a professor at the University of Arizona specializing in laboratory measurements of rates and mechanisms for reactions under extreme conditions. Besides his interest in the atmospheres of planets he also works on the understanding of ion-molecule reaction rates at the extremely low temperatures of interstellar clouds and the dynamics of low energy collisions.
Hiroshi Imanaka has been focused on the complex organic chemistry in planetary atmospheres and on the surface of icy bodies. He has conducted a novel and advanced laboratory simulation of Titan’s atmospheric chemistry using the vacuum ultraviolet light source at the Advanced Light Source at the Lawrence Berkeley National Laboratory.
The fluorescing of Titan’s upper atmosphere is clearly evident.
Purple Haze – 07.29.04
Encircled in purple stratospheric haze, Titan appears as a softly glowing sphere in this colorized image taken one day after Cassini’s first flyby of that moon.
This image shows two thin haze layers. The outer haze layer is detached and appears to float high in the atmosphere. Because of its thinness, the high haze layer is best seen at the moon’s limb.
The image was taken using a spectral filter sensitive to wavelengths of ultraviolet light centered at 338 nanometers. The image has been falsely colored: The globe of Titan retains the pale orange hue our eyes usually see, and both the main atmospheric haze and the thin detached layer have been brightened and given a purple color to enhance their visibility.
Although NASA is keen to promote the misdirection that the fluorescence [above 400 kilometres] is associated with “methane and nitrogen molecules” or that the atmosphere “preferentially scatters blue and ultraviolet wavelengths of light” the reader should be under no illusions that hydrogen is dominant in Titan’s exosphere and that it fluoresces.
ENA smoothed image of Titan’s exosphere obtained by MIMI/INCA during the Ta Titan flyby, on the 26 October 2004. The image was obtained at an altitude of approximately 8000?km with 8?min exposure time and is for hydrogen ENAs between 20 and 50?keV. The colour scale gives the ENA flux.
Hydrogen ENA smoothed image of Titan’s extended exosphere obtained by MIMI/INCA during the Tb flyby (13 December 2004), in the 20–50?keV energy range. Saturn is at the centre of the coordinate axes. The dashed circle around Titan represents the 40?000?km altitude sphere.
Titan’s exosphere and its interaction with Saturn’s magnetosphere
Iannis Dandouras, Philippe Garnier, Donald G Mitchell, Edmond C Roelof, Pontus C Brandt, Norbert Krupp and Stamatios M Krimigis
The Royal Society – Philosophical Transactions A
The similarities with the Earth are very striking – although it should be noted that beneath the outer hydrogen layer [in the Earth’s exosphere] is a layer of Helium in the plasmasphere.
The Apollo 16 mission carried a U.S. Navy ultraviolet camera that observed the stars and also produced this striking photo (far left) of hydrogen in the plasmasphere around the Earth. It was colorized (left) to show brightness variations.
Earth’s plasmasphere at 30.4 nm.
This image from the Extreme Ultraviolet Imager was taken at 07:34 UTC on 24 May 2000, at a range of 6.0 Earth radii from the center of Earth and a magnetic latitude of 73 N. (From Sandel, B. R., et al., Space Sci. Rev., 109, 25, 2003.)
Operation StratoSphere is the name I coined for a project I’ve been slowly working on over the last couple years. The short version is that it’s a project that will involve sending a few high altitude balloons up into the stratosphere with various payloads and configurations, eventually culminating in one final flight with a payload consisting of six HD cameras.