An updated dust aerosol model for Mars

The dust radiative properties derived by [1] using MRO/CRISM observations

during the 2007 planetary dust event have had some degree of utility in

various atmospheric applications, e.g., remote sensing, heating rates, etc.

Hoewver, recent work by [2] has suggested that some improvements

are needed in the 3-5 micron region. In addition, efforts by [3] to

analyze the MEX/OMEGA limb dataset have revealed some limitations in both the

the CRISM and OMEGA radiometric calibrations that have the potential to

introduce some artifacts into application of the dust properties to limb

observations as well as disk observations during high dust-loading conditions.

We begun to derive an updated set of dust refractive indices using

a combination of CRISM, OMEGA, and MRO/MARCI observations during the 2007

dust event and local optically-thick(er) dust events (i.e., Pollack crater).

This analysis includes several aspects that will provide more robust results than

the original efforts of [1]:

1) use of original OMEGA observations to more effectively constraint the

3-5 micron region; [1] used a single scattering albedo product provided by the

OMEGA Team rather than the radiances themselves;

2) an empirical "transfer" function that attempts to allow the OMEGA and CRISM

observations to provide the equivalent information, taking into account the observed

evolution in CRISM radiometry over time;

3) consideration of more realistic grain shapes that removes the artificial

backscattering enhancements provided by the analytical shape (equant cylinder)

employed by [1; see also 4].

We will summarize the results, including the relevant differences from the

original model in terms of bolometric radiative properties (small) and remote

sensing applications (larger in the 2-5 micron region).

[1] M. Wolff et al., 2009, Journal of Geophysical Research (Planets), 114, E00D04.

[2] R. T. Clancy et al., 2019, Icarus, 328, 246-273.

[3] M. Wolff et al., 2018, American Geophysical Union, Fall Meeting 2019, abstract #P43K-3896

[4] M. Wolff et al., 2010, Icarus, 208, 143-155