An HST Search for N2 emissions on Mars caused by electrical discharges during dust storms

Details An HST Search for N2 emissions on Mars caused by electrical discharges during dust storms An HST Search for N2 emissions on Mars caused by electrical discharges during dust storms

Dec 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004dps....36.3722c&link_type=abstract

American Astronomical Society, DPS meeting #36, #37.22; Bulletin of the American Astronomical Society, Vol. 36, p.1159

Astronomy and Astrophysics

Astronomy

Scientific paper

Renno et al. (2003) have proposed that electrical discharges in the Martian atmosphere produce broadband radio emission in small and large scale dust storms. Here, we present the results of a search for emissions due to the same energy source, but in the spectral region from 300 to 480 nm, where the emissions would be from the First Negative and Second Positive Systems of N2. We used archival data from the STIS instrument aboard the Hubble Space Telescope from three days in 2001: August 09, August 14 and September 04. The observations were made during pre-, mid- and late global storm conditions on Mars. The data were taken with the G430L grating, using a slit width of 0.2 arc sec, with individual exposure times of 1.0 or 1.1 sec. The observation plan was designed by the original proposers of the observations, who had different goals than we do. In particular, the original investigation was planned to have the long spatial slit scan over the surface of Mars during an exposure, so the telescope was not pointed at specific features on Mars, and the locations sampled on Mars were therefore essentially random. The spectra were binned over 10 pixels in both the spatial and spectral dimensions before analysis, which is consistent with the HST PSF. Near 480 nm, the SNR (1 sigma) was ˜ 80; and near 300 nm, the SNR was ˜30. For each of the three observation days, we synthesized a grand average spectrum for the southern half of the disk, and then formed ratio spectra with individually extracted spectra divided by the grand average, to search for emission features which deviated from the grand average spectrum at the laboratory wavelengths of N2. The result of our search was that all "features" were consistent with noise. The STIS is not currently functioning, and it would require a dedicated repair mission to the HST to restore it to operational status. If a repair were effected, future data could be improved (for this type of study) by tracking individual surface features on Mars, and by increasing both exposure times and the slit width.
Renno, N. O., A.-S. Wong and S. K. Atreya, I. dePater and M. Roos-Serote, Electrical discharges and broadband radio emission by Martian dust devils and dust storms. Geophys. Res. Lett. 30(22), 2140, 2003.

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