Temporal Behavior of Stratospheric Ammonia Abundance and Temperature Following the SL9 Impacts

Abstract

Infrared emission lines of stratospheric ammonia (NHwith cold jovian air. During the first 4 days after impact, NH 3 was present primarily at altitudes above 1 mbar with a column density of (7.7 ± 1.6) × 10 17 cm −2 after 1 day and (3.7 ± 0.8) × 10 17 cm −2 after 4 days. (Errors represent precision.) We obtained >2.5 times more NH 3 than can be supplied by nitrogen from a large cometary fragment, suggesting a primarily jovian source for the NH 3 . By 18 days postimpact, a return to quiescent upper stratospheric temperature is retrieved for the G region, with an NH 3 column density of 7.3 × 10 17 cm −2 or more in the lower stratosphere, possibly supplied by NH 3 upwelling across an impact-heated and turbulent tropopause, which may have been masked by initial dust and haze. Above the 1-mbar level, the maximum retrieved column density decreased to 6.5 × 10 16 cm −2 . Comparison to photochemical models indicates that photolysis alone is not sufficient to account for the loss of NH 3 above 1 mbar by that time, even when chemical reformation of NH 3 is ignored. We speculate that the dispersion of plume material at high altitudes (above 1 mbar) is responsible for the change in the spectra observed a few days postimpact. Data on the K impact region provide qualitatively consistent results. c 2002 Elsevier Science (USA)

On the HCN and CO2 abundance and distribution in Jupiter's stratosphere

“…They interpreted these two NH 3 components as representing, respectively, upwelling of jovian air from the troposphere, and plume deposition. Building upon a preliminary report by Kostiuk et al (1996), Fast et al (2002) found a timevarying vertical profile of NH 3 in site G, with NH 3 restricted to p < 1 mbar 1-4 days after impact but extending down to the 50 mbar level at t + 18 days, and reached similar conclusions for impact K 4 and 7 days after impact. However, unlike Griffith et al (1997), they found comparable amounts of NH 3 in the two components.…”

The aftermath of the July 2009 impact on Jupiter: Ammonia, temperatures and particulates from Gemini thermal infrared spectroscopy

“…2d). Ammonia emission from the stratosphere was previously only observed in the aftermath of the SL9 impacts (Kostiuk et al, 1996;Griffith et al, 1997;Fast et al, 2002).…”

“…However, the same experiments with the absolutely calibrated N-band spectra produced the same conclusion. The best reference profile used a decaying NH 3 mole fraction with altitude, rather than the constant vertical profiles of Fast et al (2002). This profile is physically realistic, as it represents the decreasing photochemical lifetime with altitude as UV shielding becomes less efficient.…”

“…Constant between two pressure levels: The ammonia mole fraction was held constant between two pressures, p top and p bottom , with each varying between 0.1 and 100 mbar using the same mole fractions as in experiment 2. This experiment encompasses the models suggested by Fast et al (2002) for the NH 3 distribution after SL9, namely that NH 3 was well-mixed for p < 1 mbar above the G and K impact sites 4 days after the impacts, and absent at p > 1 mbar. However, the best fits using this technique restricted NH 3 to lie between atmospheric pressures of 10 and 100 mbar, and yielded a peak mole fraction of 560 ± 300 ppb at 20-30 mbar (v 2 % 1.72).…”

Jupiter’s stratospheric hydrocarbons and temperatures after the July 2009 impact from VLT infrared spectroscopy

“…Finally, slow upwelling of tropospheric air (responsible for the presence of NH 3 in the stratosphere in both SL9 and the 2009 impacts, Griffith et al 1997;Fast et al 2002;Fletcher et al 2010) could have raised this newly-produced ethane into the lower stratosphere. But given that the small tropospheric abundance of C 2 H 6 (approximately 0.7 ppm at 200 mbar at 50 • S, Nixon et al 2007) is smaller than the quantities detected over the impact streak, some excess production of C 2 H 6 must have occurred.…”