Comet Impact Tape 7
Continued press coverage of the comet Shoemaker-Levy 9 impact on the surface of Jupiter is presented. This tape covers 21 Jul. 1994.
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Comet Impact Tape 8
Continued press coverage of the comet Shoemaker-Levy 9 impact on the surface of Jupiter is presented. This tape covers 22 Jul. 1994.
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Comet Impact Tape 3
Continued press coverage of the comet Shoemaker-Levy 9 impact on the surface of Jupiter is presented. This tape covers 17 Jul. 1994.
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Global oscillation amplitudes excited by the Jupiter-comet collision
The energy released during the collision of fragments of comet Shoemaker-Levy 9 with Jupiter in 1994 July may excite a spectrum of global oscillation modes. We estimate the maximum amplitudes to which the p-modes, discontinuity modes, inertial modes, and r-modes can be excited by assuming that the full kinetic energy of the fragment, which we take to be 10(exp 30) ergs, is converted into the energy of each individual mode. We have used two realistics Jovian models as the basis for our estimates: one with and one without the predicted 'plasma phase transition' (PPT) of hydrogen. A density discontinuity in the planet's hydrogen-helium envelope is associated with the PPT. We find that high-frequency p-modes, with periods approximately less than 15 minutes, may be excited to sufficiently large amplitudes to be observable as Doppler shifts (velocity amplitudes approximately greater than serveral m/s) or temperature variations (delta(T) approximately greater than 0.01 K) at the planetary surface. Inertial modes may also be observable. If the PPT exists in Jupiter, inertial modes with periods approximately 8 hr or approximately 2.2 days trapped in the surface region of the planet, above the PPT, may be detectable as temperature fluctuations of order delta(T) approximately 0.01 K. Inertial modes with periods of order 8-8.5 hr appear to be particularly strongly excited if the PPT exists. If the PPT does not exist in Jupiter, intertial modes with periods approximately 8-8.5 hr have much lower amplitudes. In this case, inertial modes with periods longer than approximately 18 hr may produce temperature fluctuations of order delta(T) approximately 0.01 K. Discontinuity modes associated with the PPT and r-modes unfortunately may not reach observable amplitudes.
Lee, U.↗
New jovian ring?
We follow the orbital evolution of small dust particles generated from the break up of comet Shoemaker-Levy 9 (SL9). In addition to the usual perturbations, we also consider electrostatic charging and the consequent magnetospheric effects. We show, that in about ten years following the break up, a small fraction of the dust will settle into orbits well inside the magnetosphere. The forming ring will be comprised of dust particles with radii in the range of 1.5 less than alpha less than 2.5 micrometers that follow retrograde orbits in the radial range of 4.5 less than r less than 6 R(sub J). We estimate the peak optical depth of this new ring in the range of 10(exp -8) less than tau(sub max) less than 2 x 10(exp -6).
Horanyi, Mihaly↗
Observation of Shoemaker-Levy Impacts by the Galileo Photopolarimeter Radiometer
The Galileo Photopolarimeter Radiometer experiment made direct photometric observations at 678 and 945 nanometers of several comet Shoemaker-Levy 9 fragments impacting with Jupiter. Initial flashes occurred at (fragment G) 18 July 1994 07:33:32, (H) 18 July 19:31:58, (L) 19 July 22:16:48, and (Q1) 20 July 20:13:52, equivalent Universal Time Coordinated (UTC) observed at Earth, with relative peak 945-nanometer brightnesses of 0.87, 0.67, 1.00, and 0.42, respectively. The light curves show a 2-second to maximum, a 10-second plateau, and an accelerating falloff. The Ql event, observed at both wavelengths, yielded a color temperature of more than 1 0,000 kelvin at its peak.
Martin, Terry Z.↗
Impacts with the Earth and Jupiter
The Earth has been subject to impacts from comets and asteroids since its formation, and such impacts have played an important role in the evolution of life on our planet. We now recognize not only the historical role of impacts, but the contemporary hazard posed by such events. In the absence of a complete census of potentially threatening Earth-crossing asteroids or comets (called collectively Near Earth Objects, or NEOs), or even of a comprehensive current search program to identify NEOs, we can consider the hazard only from a probabilistic perspective. In general, the larger the object the greater the hazard, even when allowance is made for the infrequency of large impacts. Most of the danger to human life is associated with impacts by objects roughly 2 km or larger (energy greater than 1 million megatons), which can inject sufficient submicrometer dust into the atmosphere to produce a severe short-term global cooling with subsequent loss of crops, leading to starvation. Hazard estimates suggest that the chance of such an event occurring during a human lifetime is about 1:5000, and the global probability of death from such impacts is of the order of 1:20000, values that can be compared with risks associated with other natural hazards such as earthquakes, volcanic eruptions, and severe storms. The widely-observed impact of Comet Shoemaker-Levy 9 with Jupiter in July 1994 provides a graphic example of such an interplanetary collision and is stimulating worldwide interest in protecting our planet against cosmic impact catastrophes.
Morrison, David↗
Kuiper Airborne Observatory's Telescope Stabilization System: Disturbance Sensitivity Reduction Via Velocity Loop Feedback
In July of 1994 the Kuiper Airborne Observatory's (KAO) Telescope Stabilization System (TSS) was upgraded to meet performance goals necessary to view the Shoemaker-Levy 9 comet collision with Jupiter. The KAO is a modified C-141 Aircraft supporting a 36 inch Infrared telescope used to gather and analyze astronomical data. Before the upgrade, the TSS exhibited approximately a 10 arc-second resolution pointing accuracy. The majority of the inaccuracy was attributable to aircraft vibration and wind buffeting entering through the aircraft's telescope door opening; in other words, the TSS was overly sensitive to external disturbances. Because of power limitations and noise requirements, improving the pointing accuracy of the telescope required more sophistication than simply raising the bandwidth as some classical control strategies might suggest. Instead, relationships were developed between the disturbance sensitivity and closed loop transfer functions. These relationships suggested that employing velocity feedback along with an increase in current loop gain would dramatically improve the pointing resolution of the TSS by decreasing the control system's sensitivity to external disturbances. With the implementation of some classical control techniques and the above philosophy, the KAO's TSS's resolution was improved to approximately 2-3 arc-seconds.
Lawrence, David P.↗
The Big Fizzle
How will the fragments of comet Shoemaker-Levy 9 meet their end, with a bang or a whimper?.
Shoemaker-Levy 9 cometary nuclei primordial solar ↗
The Impact of Comet Showmaker-Levy 9 with Jupiter
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comet Shoemaker-Levy 9 asteroid galileo Jupiter↗
FTS and Heterodyne Observatons of Jupiter from the Caltech Submm Observatory During the SL-9 Impact Period
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shifts line depths↗
Near-Infrared Imaging Spectroscopy of the Impacts of SL9 Fragments C, D, G, K, N, R, V, and W with Jupiter
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Comet Shoemaker-Levy 9↗
Comet Shoemaker-Levy Impact: Briefing
A panel discussion held on May 18, 1994, about the impact of the P/Shoemaker-Levy 9 (SL9) comet with Jupiter and its observable effects on Jupiter's atmosphere, rings, satellites, and magnetosphere, is presented. Before the panel discussion animations show the first nuclei impact, collision with Jupiter's night side (5 of the 22 known fragments of P/Shoemaker-Levy 9; N, P2, P1, Q2, and Q1), and simulated views of the Shoemaker-Levy 9 comet impact with Jupiter (from Earth and Galileo spacecraft) were presented. The panelists are: Dr. Eugene Shoemaker (from Lowell Observatory and US Geological Survey), the moderator and Shoemaker-Levy co-discoverer; Dr. Hal Weaver (from Space Telescope Science Institute); Dr. Lucy McFadden (from University of California-San Diego and the University of Maryland); Dr Melissa McGrath (from Space Telescope Science Institute); and Dr. Heidi Hammel (from Massachusetts Institute of Technology). Topics discussed include: interactions of cometary material with Jupiter's atmosphere, dynamical parameters of Jupiter's troposphere and stratosphere, and Hubble Space Telescope (HST) Observations of the SL9 Impacts on Jupiter's Atmosphere.The panel answered some of the audience's questions at the end of the discussion. This video, Part 2 (of 2), is a continuation of Part 1. It presents the second part of the question and answer session and a replay of the animations.
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Comet Shoemaker-Levy Impact: Briefing
A panel discussion held on May 18, 1994, about the impact of the P/Shoemaker-Levy 9 (SL9) comet with Jupiter and its observable effects on Jupiter's atmosphere, rings, satellites, and magnetosphere, is presented. Before the panel discussion animations show the first nuclei impact, collision with Jupiter's night side (5 of the 22 known fragments of P/Shoemaker-Levy 9; N, P2, P1, Q2, and Q1), and simulated views of the Shoemaker-Levy 9 comet impact with Jupiter (from Earth and Galileo spacecraft) were presented. The panelists are: Dr. Eugene Shoemaker (from Lowell Observatory and US Geological Survey), the moderator and Shoemaker-Levy co-discoverer; Dr. Hal Weaver (from Space Telescope Science Institute); Dr. Lucy McFadden (from University of California-San Diego and the University of Maryland); Dr Melissa McGrath (from Space Telescope Science Institute); and Dr. Heidi Hammel (from Massachusetts Institute of Technology). Topics discussed include: interactions of cometary material with Jupiter's atmosphere, dynamical parameters of Jupiter's troposphere and stratosphere, and Hubble Space Telescope (HST) Observations of the SL9 Impacts on Jupiter's Atmosphere.The panel answered some of the audience's questions at the end of the discussion. This video, Part 1 (of 2), presents the panel discussion and part of the question and answer session.
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The crash on Jupiter: Looking for answers in the impacts
Scientists are still trying to piece together what exactly occurred when comet fragments from Shoemaker-Levy 9 impacted with Jupiter last year. Several theories have been from the data received from Galileo and the Hubble Space Telescope (HST) together with the modeling of the impacts using supercomputers, scientists hope to discover the answers to their questions and perhaps to resolve the differences that have arisen between the different model simulations.
Weissman, Paul↗
Backward Integration of a SL9 Type Comet
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comet orbit Shoemaker-Levy 9 SL9↗
New Observations at the Slate Islands Impact Structure, Lake Superior
Slate Islands, a group of 2 large and several small islands, is located in northern Lake Superior, approximately 10 km south of Terrace Bay. Shatter cones, breccias and shock metamorphic features provide evidence that the Slate Islands Structure was formed as a result of asteroid or comet impact. Most of the island group is believed to represent the central uplift of a complex impact crater. The structure possibly has a diameter of about 32 km. For Sage (1978, 1991) shock metamorphic features, shatter cones and pervasive rock brecciation are the results of diatreme activity. The present investigations represent the second year of a co-operative study of the Lunar and Planetary Institute, Houston, Texas and the Field Services Section (Northwest) of the Ontario Geological Survey. The objective of this investigation is to come to a better understanding of the formation of mid-size impact structures on Earth and the planets of the solar system. Impact processes played a fundamental role in the formation of the planets and the evolution of life on Earth. Meteorite and comet impacts are not a phenomenon of the past. Last year, more than 20 pieces of the Shoemaker-Levy 9 impacted on Jupiter and the Tunguska comet impacted in Siberia in the early years of this century. The study of impact processes is a relatively young part of geoscience and much is still to be learnt by detailed field and laboratory investigations. The State Islands Structure has been selected for the present detailed investigations because of the excellent shoreline outcrops of rock units related to the impact. The structure is a complex impact crater that has been eroded so that important lithological and structural elements are exposed. We know of no other mid-size terrestrial impact structure with equal or better exposures. In this publication we present preliminary results of our 1994 and 1995 field and laboratory investigations. We have tentatively identified a few impact melt and a considerable number of suevite occurrences.
Dressler, B. O.↗
Comets: What Do We Know and Where Do We Go From Here?
Understanding of comets has made a quantum advance since 1980 due to the Earth-orbiting observatories, to fly-bys of Halley and Giacobini-Zinner, to better ground-based instruments, and to the Shoemaker-Levy 9 impact with Jupiter. The present understanding and future plans are outlined.
comets Shoemaker-Levy↗