The program conducts solar system research in support of NASA missions and of general astronomical interest. Investigations of composition, physical characteristics and changes in solar system bodies are conducted primarily using the facilities of McDonald Observatory. Progress, accomplishments, and projected accomplishments are discussed

Trafton, L.

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N92-12852
A Continued Program of Planetary Study at the University of Texas
McDonald Observatory
University of Texas at Austin
L. Trafton
Strategy
The program conducts solar system research in supp(_rt of NASA missions and of general
astronomical interest. Investigations of composition, physical characteristics and changes in
solar system bodies are conducted primarily using the facilities of McDonald Observatory.
Progress and Accomplishments
We have monitored Io's 2.1253 lam feature, which wc discovered last year, as a function of
time and of subearth longitude on Io. We have also explored the rest of Io's K-band in
search of other unidentified absorptions. None were found. In sharp contrast to Io's other
known absorptions, the feature has not been observed to vary with time (over a 1.5 year
interval) or with longitude on Io. Therefore, it can only indirectly be associated with lo's
volcanos. With our collaborators at NASA-Ames, we have ruled out sources which arc
overtones or combinations of any ()f the m¢)lecular vibrations associated with species already
identified on Io (SO,_, H:S, H.,O) or from chemical complexes of these molecules. Laboratory
experiments show that the most likely candidate is a multimer or "cluster" of CO2 molecules.
Our collected data show that very unusual periods of global scale auroral activity occurred
during September and November of 1988. This would suggest that unusual peri()ds of
widespread magnetospheric dumping occur. This contrasts with the very weak activity seen a
year later. There are long-term time scales for the Jovian auroral activity, and these arc
different for the H 2 and H3÷ emissions. There have been times, as in 1986, when the H: + was
not detectable while the H 2 emission was clearly visible. During the global scale events, the
H, and H3÷ emissions remained confined to their unusual auroral zones but strong,
unidentified emissions appeared in the vicinity of the H, quadrupole lines.
Projected Accomplishments
We will take advantage of the eclipses and occultations ()1 h) to locate the source regi(m ()n h)
of the 2.1253 lain feature. We will also obtain high res()lution FTS spectra at Kilt Peak of
this feature to establish whether it is of gaseous or s()lid origin, and to enable m()re
discriminating matches with laboratory spectra (useful for c(maposition and state studies). We
will also observe the eclipses of Galilean satellites by Io t¢) study the Na atmosphere of h).
We will continue our spectroscopic study of the Jovian auroral emissi¢ms in an attempt t¢)
understand the excitation processes and connccti¢)n with the plasma t¢)rus and lo w)lcanic
activity. Plut()'s post-perihelion changes will bc m(mitored.
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Publications
Published Papers:
1. "A Two-Component Volatile Atmosphere for Pluto I. The Bulk Hydrodynamic Escape
Regime", L. Traflon, Ap. J. 359, 512-523.
2. "Astrophysics from the Moon -- Composition and Structure of Planetary Atmospheres",
L. Trafton in Astrophysics from the Moon, (M. J. Mumma and H. J. Smith, eds.), AIP
Conference Proceedings 207, 41-44.
3. "Origin and Evolution of Planetary and Satellite Atmospheres (S. K. Atreya, J. B. Pollack,
and M. S. Matthews, Eds.), -- book review by L. Trafton, Icarus 86, 574-575.
Submitted Papers:
1. "A New Class of Absorption Feature in h_'s Near-Infrared Spectrum", L. M. Trafton,
D. F. Lester, T. F. Ramseyer, F. Salama, S. A. Sandford, and L. J. Allamandola, Icarus 89,
264-276, in press.
2. "Laboratory Studies of the Newly Discovered Infrared Band at 4705.2 cm _ (2.1253 _m) in
the Spectrum of Io: The Tentative ldentificati_m of CO2", F. Salama, S. A. Sandford, L. J.
Allamandola, L. M. Trafton, D. F. Lester, and T. F. Ramseyer, Icarus, in press.
m
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A continued program of planetary study at the University of Texas McDonald Observatory

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