Lasers discovered above Mars Pathfinder! As Mars Pathfinder prepared to deploy its rover equipped with laser navigation, Mother Nature had beaten it to the punch : Natural lasers have been discovered on mars!

Discovery of CO 2 Laser in Martian Atmosphere

Quantum Description

Vibrational energy level diagram depicting the 10.6 micron infrared transition in the carbon dioxide molecule. (The nitrogen vibrational levels shown on the right are used to enhance lasing in laboratory lasers)

Due to the low densities of the lasing species in the mesosphere and thermosphere of Mars the gain is very low, about 10 percent, comparable to single-pass gains in some earth based CO 2 lasers. The low gain is partly compensated by the extremely large volumes of active lasing medium. Over the very long distances scales, the exponential properties of amplified spontaneous emission produce a significant spectral signature at the lasing frequency. The laser amplification has been confirmed by several groups (Gordiets et al., Stepanova et al. and Dickinson et al.)

Spectra of martian CO 2 emission line as a function of frequency difference from line center (in MHz). Blue profile is the total emergent intensity in the absence of laser emission. Red profile is gaussian fit to laser emission line. Radiation is from a 1.7 arc second beam (half-power width) centered on Chryse Planitia (long +41 lat +23).

(Mumma et al., 1981)



This unusual infrared emission from CO 2 was first observed by students of Charles Townes (Johnson et al., 1976), and later identified as a 'natural laser'. The lines are 100 million times brighter than what would be expected if thermodynamic equilibrium was established. The laser emission line can be used as a diagnostic probe of the temperature and wind patterns on Mars (Mumma, 1993) and Venus (Goldstein, 1991).

Bow and Arrow Analogy The emission of a laser photon by an excited CO 2 molecule (below) can be compared to the release of energy stored in a bow (above) : When the molecule vibrates or changes its geometry, it snaps back and emits a photon like a bow launching an arrow.

Image courtesy Dale Gustafson and the National Geographic Society ©

Goddard Space Flight Center IR heterodyne spectrometer. The CO 2 laser beam from the bottom (vLO) is mixed with the input signal (vIR) coming in from the left. The sensitive IR photodetector produces an electronic signal at the upper right (vLO-vIR) which is further processed by an RF spectrometer (not shown). Kostiuk and Mumma (1983).



Practical Use

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There are proposals for realizing a planetary scale laser by placing mirrors in appropriate orbits about the planet to enhance the gain and produce oscillation. (Sherwood, 1988, 1992)

Heterodyne Spectroscopy