Shoemaker-Levy Research Articles

Legend descent of Ganga and similarities with impact event

Role of comets and icy asteroids in getting water to Earth is under discussion for last few decades. In the recent history, we have observed and recorded two comet impact events in the solar system. Both the impacts of solwind and Shoemaker levy-9 support the argument that the impacts by comets may be a regular feature and Earth is no exception to it. In the history of mankind, there is a strong possibility that such events were observed by various civilizations.Early settlements of ancient India observed various celestial objects like stars, constellations, planets and comets.Vedas like Rigveda, Atharvaveda refer comets as “Dhumketu”. Certain hymns of Rig Vedastrongly support the possibility of impact event being observed and recorded as eyewitness account. Reference of these celestial bodies is found in various ancient legends of India. These legends may be work of imagination based on real observations. One such legend is descent of Ganga from heaven. As per Valmiki Ramayana many aspects of this legend like its composition, appearance, descent path and effects at the time of descent have close resemblance with the impact event of a celestial body like comet. Ancient Stone carvings depicting the event provide major clue about the celestial movement and the impact event.In this paper we have used ancient description from Ramayana and Veda, and compared it with modern scientific facts and geological features of the region described in the legend.There are Multiple water bodies and lakes in the Tibet behind mount Kailash. This lake region is rich with finds like coesite, stishovite and other ultra high pressure finds that are usually associated with the impact site. These lakes play crucial role in the water cycle of Asia.Though there are lot of similarities in the legend and the available facts, as on date there is no conclusive evidence which can prove the origin of river Gangaas a result of this event as mentioned in thelegend. Thus this legend may be a result of observations mixed with belief.

Invariant Manifolds and the Capture of Comet Shoemaker-Levy 9★

Abstract The impact of Comet Shoemaker-Levy 9 (SL9) with Jupiter in 1994 was the ultimate confirmation of Eugene Shoemaker’s theory that impacts are a common, fundamental process in the Solar System. On Earth, asteroid impacts have produced several near extinction level events. We tend to visualise these collisions as billiard balls hitting one another. But how, exactly, do they occur? The actual dynamics is much more complex and subtle because it is highly non-linear and involves chaos in the three-body problem. In this paper we investigate the effects of Lyapunov orbits, halo orbits, and their associated invariant manifolds, on the orbital motion of SL9. We demonstrate that periodic orbits act as gateways to Jupiter, and their invariant manifolds controlled the dynamics of SL9 during the initial capture phase.

SUBMILLIMETER OBSERVATION OF JUPITER’S STRATOSPHERIC COMPOSITION: DETECTION OF CARBON MONOSULFIDE (J = 7 − 6) 19 YEARS AFTER THE COMETARY IMPACT

ABSTRACT In Jupiter's stratosphere, gaseous carbon monosulfide (CS) was first discovered in 1994 by millimeter and ultraviolet observations as a product induced by the collision of comet Shoemaker–Levy 9 (SL9). To constrain sulfur chemistry, in 2013, 19 years after the SL9 event, we observed Jupiter's stratospheric CS J = 7 − 6 rotational transition at 0.8 mm wavelength by using the Atacama Submillimeter Telescope Experiment 10 m single-dish telescope. The CS molecular line was successfully detected with 120 mK intensity in the antenna temperature scale. The obtained CS total mass shows ∼90% decrease relative to that observed in 1998. From the line shape analysis, CS is suggested to be present above the mbar pressure level, which is comparable to that determined in 1998.

My LIFE AS A COMET HUNTER.

The article offers the author's insights on his dedication to become a professional comet hunter. The author discusses his early memories of learning the French language to pass an examination, his discovery on the movement of a fuzzy object, and the new comets he discovered including the Comet Shoemaker-Levy 9, which was the first comet that crashed in the planet Jupiter.

Ecological Management and the Cosmogenic Mechanism of Earthquakes

Critical issue of ecological risk management in urban areas is to predict the evolution of the dangerous natural processes intensity. The special situation in the realization of these risks take the earthquake threat and the stresses emergency fluctuations in the geological environment of the buildings and structures bases. This article is devoted to one of the main problems of earthquake engineering - verification of the dominant mechanisms and causality of the earthquakes intensity dangerous evolution. In it discusses the comparative analysis results of the Earth gravitational interaction energy variations amplitudes with the Sun, with the Moon and the solar system planets. Also presented the comparative evaluations results of the Earth geospheres gravitational perturbations amplitudes with the Earth solar radiation energy with the energy of its own heat of the Earth. It is shown that the energy of his own heat and Sun exposure of the Earth much less energy to gravitational perturbations in the near-earth space. In the article presents the spectral analysis results of earthquakes global daily energy on the Earth before and after the Shoemaker-Levy comet explosion on Jupiter. It is shown that the seismic events number on Earth with magnitude greater than 2.5 on the Richter scale after the comet explosion increased in 10 times. In the earthquakes global daily energy spectrum shows the spectral manifestations of solar system planets gravitational resonances. In given article the researches results of natural disasters cosmogenic sources power allow us to argue that ecological risk effective management is impossible without the evolution forecast of the cosmogenic effects intensity on natural processes for sustainable urban development.

Spatial distribution of water in the stratosphere of Jupiter fromHerschelHIFI and PACS observations

Context. In the past 15 years, several studies suggested that water in the stratosphere of Jupiter originated from the Shoemaker-Levy 9 (SL9) comet impacts in July 1994, but a direct proof was missing. Only a very sensitive instrument observing with high spectral/spatial resolution can help to solve this problem. This is the case of the Herschel Space Observatory, which is the first telescope capable of mapping water in Jupiter’s stratosphere.Aims. We observed the spatial distribution of the water emission in Jupiter’s stratosphere with the Heterodyne Instrument for the Far Infrared (HIFI) and the Photodetector Array Camera and Spectrometer (PACS) onboard Herschel to constrain its origin. In parallel, we monitored Jupiter’s stratospheric temperature with the NASA Infrared Telescope Facility (IRTF) to separate temperature from water variability.Methods. We obtained a 25-point map of the 1669.9 GHz water line with HIFI in July 2010 and several maps with PACS in October 2009 and December 2010. The 2010 PACS map is a 400-point raster of the water 66.4 μ m emission. Additionally, we mapped the methane ν 4 band emission to constrain the stratospheric temperature in Jupiter in the same periods with the IRTF.Results. Water is found to be restricted to pressures lower than 2 mbar. Its column density decreases by a factor of 2−3 between southern and northern latitudes, consistently between the HIFI and the PACS 66.4 μ m maps. We infer that an emission maximum seen around 15 °S is caused by a warm stratospheric belt detected in the IRTF data. Conclusions. Latitudinal temperature variability cannot explain the global north-south asymmetry in the water maps. From the latitudinal and vertical distributions of water in Jupiter’s stratosphere, we rule out interplanetary dust particles as its main source. Furthermore, we demonstrate that Jupiter’s stratospheric water was delivered by the SL9 comet and that more than 95% of the observed water comes from the comet according to our models.

Odin space telescope monitoring of water vapor in the stratosphere of Jupiter

The Odin space telescope has monitored the H2O (110–101) line in Jupiter's stratosphere over the 2003–2009 period. When comparing these data with previous spectra obtained with SWAS and Odin over the 1999–2002 period, we see no significant variations in the line-to-continuum ratio of the H2O line over the whole period. We have however tentatively identified a decrease by ∼15% of the line-to-continuum ratio between 2002 and 2007–2009, indicating that there was less H2O in the stratosphere of Jupiter in 2007–2009 than anticipated. We have tested the IDP (interplanetary dust particles) and SL9 (Shoemaker-Levy 9) 1D time-dependent models presented in Cavalié et al. [2008, Observation of water vapor in the stratosphere 613 of Jupiter with the Odin space telescope. Planetary and Space Science 56, 1573–1584]. We present a series of scenarios that lead to satisfactory fits of the whole data set (1999–2002 and 2003–2009 periods) based on IDP and SL9 models. The evolution of Jupiter's stratospheric H2O that we have tentatively observed has however to be confirmed by Herschel/HIFI observations. If the decrease of the line-to-continuum ratio is confirmed by future observations, it would be a direct evidence that Jupiter's H2O comes from SL9. In addition, this study shows that new constraints on Jupiter's eddy diffusion coefficient profile could be obtained (in the pressure ranges that are probed) from the monitoring of SL9 species in its stratosphere.

The atmospheric influence, size and possible asteroidal nature of the July 2009 Jupiter impactor

Near-infrared and mid-infrared observations of the site of the 2009 July 19 impact of an unknown object with Jupiter were obtained within days of the event. The observations were used to assess the properties of a particulate debris field, elevated temperatures, and the extent of ammonia gas redistributed from the troposphere into Jupiter’s stratosphere. The impact strongly influenced the atmosphere in a central region, as well as having weaker effects in a separate field to its west, similar to the Comet Shoemaker-Levy 9 (SL9) impact sites in 1994. Temperatures were elevated by as much as 6 K at pressures of about 50–70 mbar in Jupiter’s lower stratosphere near the center of the impact site, but no changes above the noise level (1 K) were observed in the upper stratosphere at atmospheric pressures less than ∼1 mbar. The impact transported at least ∼2 × 10 15 g of gas from the troposphere to the stratosphere, an amount less than derived for the SL9 C fragment impact. From thermal heating and mass-transport considerations, the diameter of the impactor was roughly in the range of 200–500 m, assuming a mean density of 2.5 g/cm 3. Models with temperature perturbations and ammonia redistribution alone are unable to fit the observed thermal emission; non-gray emission from particulate emission is needed. Mid-infrared spectroscopy of material delivered by the impacting body implies that, in addition to a silicate component, it contains a strong signature that is consistent with silica, distinguishing it from SL9, which contained no evidence for silica. Because no comet has a significant abundance of silica, this result is more consistent with a “rocky” or “asteroidal” origin for the impactor than an “icy” or “cometary” one. This is surprising because the only objects generally considered likely to collide with Jupiter and its satellites are Jupiter-Family Comets, whose populations appear to be orders of magnitude larger than the Jupiter-encountering asteroids. Nonetheless, our conclusion that there is good evidence for at least a major asteroidal component of the impactor composition is also consistent both with constraints on the geometry of the impactor and with results of contemporaneous Hubble Space Telescope observations. If the impact was not simply a statistical fluke, then our conclusion that the impactor contained more rocky material than was the case for the desiccated Comet SL9 implies a larger population of Jupiter-crossing asteroidal bodies than previously estimated, an asteroidal component within the Jupiter-Family Comet population, or compositional differentiation within these bodies.

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

We obtained longitudinally resolved thermal infrared spectra (8–13 μm and 17–25 μm) of Jupiter’s impact debris at the Gemini South Telescope on July 24, 2009; five days after the July 19th collision. These were used to study the mechanisms responsible for the redistribution of thermal energy and material (ammonia and stratospheric particulates) following the impact. Upwelling of (8.5 ± 4.1) × 10 14 g of tropospheric air was sufficient to deposit (6.7 ± 4.1) × 10 12 g of NH 3 over a 6° longitude range above the impact core. The NH 3 was distributed over the 20–80 mbar region with a peak abundance of 1.0 ± 0.6 ppm at 45 mbar. Only a 10th of this abundance was observed over the western ejecta, and it is unlikely that these observations were sensitive to NH 3 entrained in the ballistic plume itself. The pattern of excess thermal energy was markedly different from that of Shoemaker-Levy 9 (SL9), with a localized tropospheric perturbation of 2.0 ± 1.0 K at 200–300 mbar and a broader stratospheric warming of up to 3.5 ± 2.0 K at 10–30 mbar. We find no evidence of residual warmth at p < 1 mbar five days after the impact. The excess thermal energy places lower limits on the total energy of the impact (1.8–15.7 × 10 26 ergs), which limits the impactor diameter to 70–510 m (depending on the bulk density chosen for the material). The models of the Gemini spectra required three distinct aerosol features, indicative of the mineralogy of the dark particulate debris, centred at 9.1, 10.0 and 18.5 μm. The retrieved opacities for each of these features were distributed over a larger area (9–10° longitude) and at higher altitudes (above the 10-mbar level) than the stratospheric NH 3, and they are more spatially inhomogeneous. This implies the particulates were either entrained with the rising hot plume or created upon plume re-entry and are subsequently redistributed by stratospheric winds. The three particulate features were consistent with a mixture of amorphous iron and magnesium-rich silicates and silicas in the debris field. A broad 10-μm signature was coincident with peaks expected from material rich in amorphous olivines (but poor in pyroxenes), and similar to silicate features observed during SL9. A narrow 9.1-μm signature was interpreted as a combination of amorphous and crystalline silica. Finally, a broad 18.5-μm emitter was not adequately reproduced by a mixture of simple olivines and pyroxenes and remains to be identified.

THE IMPACT OF A LARGE OBJECT ON JUPITER IN 2009 JULY

On 2009 July 19, we observed a single, large impact on Jupiter at a planetocentric latitude of 55^{\circ}S. This and the Shoemaker-Levy 9 (SL9) impacts on Jupiter in 1994 are the only planetary-scale impacts ever observed. The 2009 impact had an entry trajectory opposite and with a lower incidence angle than that of SL9. Comparison of the initial aerosol cloud debris properties, spanning 4,800 km east-west and 2,500 km north-south, with those produced by the SL9 fragments, and dynamical calculations of pre-impact orbit, indicate that the impactor was most probably an icy body with a size of 0.5-1 km. The collision rate of events of this magnitude may be five to ten times more frequent than previously thought. The search for unpredicted impacts, such as the current one, could be best performed in 890-nm and K (2.03-2.36 {\mu}m) filters in strong gaseous absorption, where the high-altitude aerosols are more reflective than Jupiter's primary cloud.

On the HCN and CO 2 abundance and distribution in Jupiter's stratosphere

Observations of Jupiter by Cassini/CIRS, acquired during the December 2000 flyby, provide the latitudinal distribution of HCN and CO 2 in Jupiter's stratosphere with unprecedented spatial resolution and coverage. Following up on a preliminary study by Kunde et al. [Kunde, V.G., and 41 colleagues, 2004. Science 305, 1582–1587], the analysis of these observations leads to two unexpected results (i) the total HCN mass in Jupiter's stratosphere in 2000 was ( 6.0 ± 1.5 ) × 10 13 g , i.e., at least three times larger than measured immediately after the Shoemaker–Levy 9 (SL9) impacts in July 1994 and (ii) the latitudinal distributions of HCN and CO 2 are strikingly different: while HCN exhibits a maximum at 45° S and a sharp decrease towards high Southern latitudes, the CO 2 column densities peak over the South Pole. The total CO 2 mass is ( 2.9 ± 1.2 ) × 10 13 g . A possible cause for the HCN mass increase is its production from the photolysis of NH 3, although a problem remains because, while millimeter-wave observations clearly indicate that HCN is currently restricted to submillibar ( ∼ 0.3 mbar ) levels, immediate post-impact infrared observations have suggested that most of the ammonia was present in the lower stratosphere near 20 mbar. HCN appears to be a good atmospheric tracer, with negligible chemical losses. Based on 1-dimensional (latitude) transport models, the HCN distribution is best interpreted as resulting from the combination of a sharp decrease (over an order of magnitude in K y y ) of wave-induced eddy mixing poleward of 40° and an equatorward transport with ∼ 7 cm s −1 velocity. The CO 2 distribution was investigated by coupling the transport model with an elementary chemical model, in which CO 2 is produced from the conversion of water originating either from SL9 or from auroral input. The auroral source does not appear adequate to reproduce the CO 2 peak over the South Pole, as required fluxes are unrealistically high and the shape of the CO 2 bulge is not properly matched. In contrast, the CO 2 distribution can be fit by invoking poleward transport with a ∼ 30 cm s −1 velocity and vigorous eddy mixing ( K y y = 2 × 10 11 cm 2 s −1 ). While the vertical distribution of CO 2 is not measured, the combined HCN and CO 2 results imply that the two species reside at different stratospheric levels. Comparing with the circulation regimes predicted by earlier radiative-dynamical models of Jupiter's stratosphere, and with inferences from the ethane and acetylene stratospheric latitudinal distribution, we suggest that CO 2 lies in the middle stratosphere near or below the 5-mbar level.

Shoemaker‐Levy 9 Impact Modeling. I. High‐Resolution Three‐dimensional Bolides

We have run high-resolution, three-dimensional, hydrodynamic simulations of the impact of comet ShoemakerLevy 9into the atmosphereof Jupiter.Wefindthat the energydeposition profile islargely similar to theprevious twodimensional calculations of Mac Low & Zahnle, although perhaps somewhat broader in the range of height over which the energy is deposited. As with similar calculations for impacts into the Venusian atmosphere, there is considerablesensitivityintheresultstosmallchangesintheinitialconditions,indicatingdynamicalchaos.Wecalculated the median depth of energy deposition (the height z at which 50% of the bolide’s energy has been released) per run. The mean value among runs is � 70 km below the 1 bar level, for a 1 km diameter impactor of porous ice of density � ¼ 0: 6gc m � 3 . The standard deviation among these runs is 14 km. We find little evidence of a trend in these results with the resolution of the calculations (up to 57 cells across the impactor radius, or 8.8 m resolution), suggesting that resolutions as low as 16 grid cells across the radius of the bolide may yield good results for this particular quantity. Visualization of the bolide breakup shows that the ice impactors were shredded and/or compressed in a complicated manner but evidently did not fragment into separate, coherent masses, unlike calculations for basalt impactors. The processes that destroy the impactor take place at significantly shallower levels in the atmosphere (�� 40 km for a 1 km diameterbolide), but the shreddedremains haveenoughinertia to carry themdownanother scale heightor more before they lose their kinetic energy. Comparison of basalt impactor models shows that energy deposition curves for these objects have much less sensitivity to initial conditions than do ice impactors, which may reflect differences in the equation of state forthedifferentkinds of objects, or a scale-dependentbreakup phenomenology, with the preferred scaledependingonimpactordensity.Modelsofimpactorscoveringa � 600-foldrangeofmass(m)showthatlarger impactors descend slightly deeper than expected from scaling the intercepted atmospheric column mass by the impactor mass. Instead, the intercepted column mass scales as m 1.2 . Subject headingg comets: individual (Shoemaker-Levy 9) — hydrodynamics

The inertia-gravity waves caused by the impact of shoemaker-levy 9 with jupiter

After the collision of Comet Shoemaker-Levy 9 (SL9) with Jupiter, some ring structures were observed propagating outwards at a constant speed (∼450 m/s) on the Jovian surface. These are thought to be linear waves caused by the collision. A linear model of the collision is presented, in which the Jovian atmosphere is considered as an irrotational, inviscid, stratified and incompressible fluid layer moving at a speed of U = b + az. We take an initial impulsive pressure p(r; 0) as the initial condition and solve the fluid dynamics equations for inertia-gravity waves. It is found that most part of the perturbation energy is used to produce internal waves when Jovian atmosphere moves at a constant speed (U = Uo (∼170 m/s)). A relation between the impact depth H and the horizontal phase speed vp is deduced. Finally, the inertia-gravity waves are discussed for the case U = b + az and it is found that the perturbation energy is then not divided equally between kinetic energy and potential energy because of the effect of a shear.

Meridional transport of HCN from SL9 impacts on Jupiter

In July 1994, the Shoemaker–Levy 9 (SL9) impacts introduced hydrogen cyanide (HCN) to Jupiter at a well confined latitude band around −44°, over a range of specific longitudes corresponding to each of the 21 fragments (Bézard et al. 1997, Icarus 125, 94–120). This newcomer to Jupiter's stratosphere traces jovian dynamics. HCN rapidly mixed with longitude, so that observations recorded later than several months after impact witnessed primarily the meridional transport of HCN north and south of the impact latitude band. We report spatially resolved spectroscopy of HCN emission 10 months and 6 years following the impacts. We detect a total mass of HCN in Jupiter's stratosphere of 1.5±0.7×10 13 g in 1995 and 1.7±0.4×10 13 g in 2000, comparable to that observed several days following the impacts (Bézard et al. 1997, Icarus 125, 94–120). In 1995, 10 months after impact, HCN spread to −30° and −65° latitude (half column masses), consistent with a horizontal eddy diffusion coefficient of K yy =2–3×10 10 cm 2 s −1. Six years following impact HCN is observed in the northern hemisphere, while still being concentrated at 44° south latitude. Our meridional distribution of HCN suggests that mixing occurred rapidly north of the equator, with K yy =2–5×10 11 cm 2 s −1, consistent with the findings of Moreno et al. (2003, Planet. Space Sci. 51, 591–611) and Lellouch et al. (2002, Icarus 159, 112–131). These inferred eddy diffusion coefficients for Jupiter's stratosphere at 0.1–0.5 mbar generally exceed those that characterize transport on Earth. The low abundance of HCN detected at high latitudes suggests that, like on Earth, polar regions are dynamically isolated from lower latitudes.

Geosciences. Impact cratering comes of age.

In 1994, fragments of comet Shoemaker-Levy 9 smashed into the atmosphere of Jupiter. The event illustrated how important impact cratering has been, and still is, for all solid bodies in the solar system. In his Perspective, [Reimold][1] charts the history of research into impact cratering, which began in earnest when the Apollo missions returned lunar samples. Many of these samples showed signs of shock deformation that could only have been created by major impacts. Today, there is evidence for past impact events throughout Earth's history. Major impact have been implicated in several mass extinctions, and surveys and space exploration are investigating the future threat from asteroid and comet impact to humankind. [1]: http://www.sciencemag.org/cgi/content/full/300/5627/1889

Where have all the comets gone?

Comets are the fossils of the solar system. From their chemical composition to the path they cut across the sky, they convey a wealth of information about how the planets first formed. Events such as the demise of Comet Shoemaker-Levy 9 offer clues about whether a similar collision is in Earth's future. But because sightings of these objects are so rare, astronomers must use computer simulations to fill the knowledge gap. Planetary scientist Hal Levison and his colleagues at the Southwest Research Institute (SWRI) in San Antonio, Texas, recently drew on two computer models to solve the mystery of why we see so few comets.

The Origin of Water Vapor and Carbon Dioxide in Jupiter's Stratosphere

Observations of H 2O rotational lines from the Infrared Space Observatory (ISO) and the Submillimeter Wave Astronomy Satellite (SWAS) and of the CO 2 ν 2 band by ISO are analyzed jointly to determine the origin of water vapor and carbon dioxide in Jupiter's stratosphere. Simultaneous modelling of ISO/LWS and ISO/SWS observations acquired in 1997 indicates that most of the stratospheric jovian water is restricted to pressures less than 0.5±0.2 mbar, with a disk-averaged column density of (2.0±0.5)×10 15 cm −2. Disk-resolved observations of CO 2 by ISO/SWS reveal latitudinal variations of the CO 2 abundance, with a decrease of at least a factor of 7 from mid-southern to mid-northern latitudes, and a disk-center column density of (3.4±0.7)×10 14 cm −2. These results strongly suggest that the observed H 2O and CO 2 primarily result from the production, at midsouthern latitudes, of oxygenated material in the form of CO and H 2O by the Shoemaker–Levy 9 (SL9) impacts in July 1994 and subsequent chemical and transport evolution, rather than from a permanent interplanetary dust particle or satellite source. This conclusion is supported by quantitative evolution model calculations. Given the characteristic vertical mixing times in Jupiter's stratosphere, material deposited at ∼0.1 mbar by the SL9 impacts is indeed expected to diffuse down to the ∼0.5 mbar level after 3 years. A coupled chemical-horizontal transport model indicates that the stability of water vapor against photolysis and conversion to CO 2 is maintained over typically ∼50 years by the decrease of the local CO mixing ratio associated with horizontal spreading. A model with an initial (i.e., SL9-produced) H 2O/CO mass mixing ratio of 0.07, not inconsistent with immediate post-impact observations, matches the observed H 2O abunda nce and CO 2 horizontal distribution 3 years after the impacts. In contrast, the production of CO 2 from SL9-produced CO and a water component deriving from an interplanetary dust component is insufficient to account for the observed CO 2 amounts. The observations can further be used to place a stringent upper limit (8×10 4 cm −2 s −1) on the permanent water influx into Jupiter. This may indicate that the much larger flux observed at Saturn derives dominantly from a ring source, or that the ablation of micrometeoroids leads dominantly to different species at Saturn (H 2O) and Jupiter (CO). Finally, the SWAS H 2O spectra do not appear fully consistent with the ISO data and should be confirmed by future ODIN and Herschel observations.

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

Infrared emission lines of stratospheric ammonia (NH 3) were observed following the collisions of the fragments of Comet Shoemaker–Levy 9 with Jupiter in July of 1994 at the impact sites of fragments G and K. Infrared heterodyne spectra near 10.7 μm were obtained by A. Betz et al. (in Abstracts for Special Sessions on Comet Shoemaker-Levy 9, The 26th Meeting of the Division for Planetary Sciences, Washington DC, 31 Oct.–4 Nov. 1994, p. 25) using one of the Infrared Spatial Interferometer telescope systems on Mount Wilson. Lineshapes of up to three different NH 3 emission lines were measured at a resolving power of ∼10 7 at multiple times following the impacts. We present here our radiative transfer analysis of the fully resolved spectral lineshapes of the multiple rovibrational lines. This analysis provides information on temperature structure and NH 3 abundance distributions and their temporal changes up to 18 days after impact. These results are compared to photochemical models to determine the role of photochemistry and other mechanisms in the destruction and dilution of NH 3 in the jovian stratosphere after the SL9 impacts. One day following the G impact, the inferred temperature above 0.001 mbar altitude is 283±13 K, consistent with a recent plume splashback model. Cooling of the upper stratosphere to 204 K by the fourth day and to quiescence after a week is consistent with a simple gray atmosphere radiative flux calculation and mixing with 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.

Models of the Shoemaker‐Levy 9 Impacts. II. Radiative‐Hydrodynamic Modeling of the Plume Splashback

We model the plume ii splashback ˇˇ phase of the Shoemaker-Levy 9 (SL9) collisions with Jupiter. We modi—ed the ZEUS-3D hydrodynamic code to include radiative transport in the gray approximation and present validation tests. After initializing with a model Jovian atmosphere, we couple mass and momentum —uxes of SL9 plume material, as calculated by the ballistic Monte Carlo plume model of Paper I of this series. A strong and complex shock structure results. The shock temperatures produced by the model agree well with observations, and the structure and evolution of the modeled shocks account for the appearance of high-excitation molecular line emission after the peak of the continuum light curve. The splashback region cools by radial expansion as well as by radiation. The morphology of our synthetic continuum light curves agrees with observations over a broad wavelength range (0.9¨12 km). Much of the complex structure of these light curves is a natural consequence of the temperature dependence of the Planck function and the plume velocity distribution. A feature of our ballistic plume is a shell of mass at the highest velocities, which we term the ii vanguard.ˇˇ Portions of the vanguard ejected on shallow trajectories produce a lateral shock front, whose initial expansion accounts for the ii third precursors ˇˇ seen in the 2 km light curves of the larger impacts and for hot methane emission at early times observed by Dinelli and coworkers. Continued propagation of this lateral shock approximately reproduces the radii, propagation speed, and centroid positions of the large rings observed at 3¨4 k mb y McGregor and coworkers. The portion of the vanguard ejected closer to the vertical falls back with high z-component velocities just after maximum light, producing CO emission and the ii —are ˇˇ seen at 0.9 km. The model also produces secondary maxima (ii bounces ˇˇ), whose amplitudes and periods are in agreement with observations.

Fabry–Perot Imaging of Jupiter's Aurora at 2.1 μm

Jupiter was imaged in the near-infrared K band on July 22–24, 1994, i.e., shortly after the impact of Comet Shoemaker–Levy 9 (S-L9). Using the IRAC-2b near-infrared camera with Fabry–Perot-interferometer at the MPG/ ESO 2.2-m Telescope of the European Southern Observatory on La Silla in Chile, we obtained full disk images of Jupiter's H + 3 and H 2 emission at 2.093 and 2.121 μm, respectively. In two nights almost one full jovian rotation was covered. Our observations represent the first ground-based narrow-band images of Jupiter's H + 3 and H 2 emission in the K band. No impact-related line emission is detected. In the north polar cap the aurora is clearly visible at 2.093 μm. Some emission at 2.121 μm appears close to the limb. It has different morphology and a different λ III dependence and is fainter than the H + 3 emission. Despite H 2 being a major auroral emitter in the far-UV spectral range it is not clear how its infrared emission relates to auroral phenomena. Shortly after the S-L9 impacts the intensity at 2.093 μm is slightly larger and at 2.121 μm the intensity is three times larger as compared to values provided by Drossart et al. (1989, Nature 340, 539–541). No emissions are detected in the south polar cap. This agrees with observations in the L band (Miller et al. 1997, Planet. Space Sci. 45, 1237–1250). The north polar aurora was close to normal and its vibrational temperature close to 1100 K. The Io footprint is not visible.