__________________________________________________________________________ T H E O L E R O E M E R M E S S E N G E R _______________________________________________ JJJJ C G JJJJJJ I E JJJJ __________________________________________________________________________ Newsletter of the International Jupiter Watch Satellite Discipline E-mail issue 7 February 18th, 1994 Editor and Discipline Leader: John Spencer Voice: (602) 774-3358 Lowell Observatory Fax: (602) 774-6296 1400 W. Mars Hill Rd. Internet: spencer@lowell.edu Flagstaff, AZ 86001 ------------------------------------------------------------------------------ EDITORIAL COMMENTS Part of the reason newsletters are coming more frequently now is that I'm no longer attempting the time-consuming mailing of hardcopies. So if you know of people expecting hardcopies of these newsletters, let them know that it's e-mail or nothing! This issue contains information on the identity of the SL9 fragments, the recent Icy Galilean Satellites conference, and upcoming HST and ground-based observations of the satellites. I'd still like to include a more complete list of new publications and preprints in future issues. Please send me the information, as well as anything else you'd like me to include here. ------------------------------------------------------------------------------ SHOEMAKER-LEVY I just posted the following message to the Maryland comet crash bulletin board: ------------- Here is a list of the recommended names and the appearance of all the nuclei visible in the post-conjunction images, including the press-released January HST image. Hopefully this will help to clear up some recent confusion! John Spencer Brian Marsden Zdenek Sekanina Don Yeomans Paul Chodas February 18, 1994. A GIF-format file of the January HST image of SL9 can be downloaded from JPL (anonymous ftp to "jplinfo.jpl.nasa.gov", directory "news", file name is "sl9hst.gif"). It's also in the Feb 14 issue of Aviation Week. Here's an identification of the various comet nuclei in this image. The letter designations are informal but we suggest we all use them for consistency from now on, especially in the confusing P/Q region. The names "P" and "Q" (or "8" and "7") should be used if their individual components cannot be resolved. The description proceeds from astronomical East to West, in the same order as the impacts. For orientation, note that the tails stream off to the north-west. The Aviation Week image has north at the bottom. A=21 The easternmost nucleus, visible in the original press realease and the Aviation Week reproduction, but clipped from the GIF image at the left margin. B=20 The eastmost nucleus on the GIF image, displaced north slightly from the general trend. C=19, The next three nuclei, all on the general trend, from east to west. D=18, D=18 is the faintest, E=17 the brightest. These three are followed E=17 by a wider gap. F=16 A relatively faint nucleus displaced north from the general trend. G=15 A bright nucleus colinear with the general trend, quite close to F=16, followed by a wide gap. H=14 A bright nucleus colinear with most of the others, followed by a particularly wide gap. J=13 This nucleus is invisible in the HST image and has apparently disappeared. K=12 A bright nucleus colinear with the general trend, followed by a wide gap. L=11 A bright nucleus colinear with the general trend, followed by a wide gap. M=10 This nucleus is invisible in the HST image and has apparently disappeared. N=9 A faint nucleus about 2/3 of the way between L=11 and Q=7. P=8 A blend of two nuclei, P1 and P2, displaced north from the general trend, resolvable in the HST images. P2=8b A moderately bright nucleus, the east member of the pair, just separable from P1 in the July 1993 HST image. P1=8a The faint nucleus immediately to the west of P2 It is also visible in the July 1993 HST image. Q=7 The brightest nucleus, resolvable as two nuclei, Q1 and Q2, in the HST images. Q2=7b A moderately bright nucleus immediately north of Q1. It is just visible, much closer to Q1, in the July 1993 HST image. Q1=7a The southern, brighter, nucleus of the Q pair. R=6 A moderately faint nucleus to the west of Q=7, colinear with the general trend, and followed by a wider gap. S=5 A moderately bright nucleus colinear with the general trend. T=4 A faint nucleus to the northwest of S=5, displaced north from the general trend. U=3 Possibly visible at the extreme west side of the new HST image, but very faint. V=2, Clipped off the west side of the HST image. W=1 A pictorial representation of the above information follows. Nuclei are designated by ".","o", and "*", in order of increasing brightness. EAST . A=21 . B=20 . C=19 . D=18 o E=17 o F=16 * G=15 * H=14 * K=12 NORTH * L=11 . N=9 o P2=8b } P=8 . P1=8a } *o Q1=7a,Q2=7b } Q=7 o R=6 * S=5 . T=4 . U=3 . V=2 o W=1 WEST ------------------------------------------------------------------------------ FILTERS FOR THE SHOEMAKER-LEVY IMPACT We had a strong response to the request of filter orders, and Omega Optical now has all the orders and is starting construction of them. Expected delivery is in May, earlier than originally feared. ------------------------------------------------------------------------------ ICY GALILEAN SATELLITES CONFERENCE San Juan Capistrano Research Institute, February 1-3, 1994 Relatively new results presented at the meeting included: the possibility that Ganymede has undergone significant tidal heating during its orbital evolution (Malhotra, Showman); estimation of cratering rates on the satellites being many times higher than at Earth, higher than previously thought (Shoemaker); "rediscovery" of the very different visible-wavelength continuum shape for Europa compared to Ganymede and Callisto (Spencer); a search (so far unsuccessful) for OH emission near Europa, and much improved Europa UV continuum measurements, with HST (Noll); unexpectedly low mm-wavelength brightness temperatures for the satellites, and constraints on solid-state greenhouses (Betts); the possible importance of salts in surface and interior evolution (Kargel, Hogenboom); and possibly endogenic albedo patterns on Callisto, and a mysterious radial groove system near its north pole Schenk). There was also extensive discussion of Galileo plans. Despite the painful data limits imposed by the loss of the high-gain antenna, a few high-resolution images of all major terrain types on the satellites will be possible, NIMS and PPR coverage will be very extensive, and UV reflectance mapping (down to 1100 A!) and atmospheric searches will be done by the UVS, at least for Ganymede and Callisto. Gravity measurements will be able to detect differentiation inside Ganymede and Europa, but unfortunately Callisto will be marginal. At the end of the meeting we discussed observational work that would provide useful support for the Galileo mission (one of the major roles of the IJW). Though there is little need to monitor time-variable phenomena, unlike the case of Io, we noted several cases where Earth-based observations could be improved and would help in interpreting the Galileo data, as follows: 1) Improved visible and IR spectrophotometry for calibration of disk-resolved SSI and NIMS observations. 2) Wavelength dependence of opposition effects, and zero-phase spectrophotometry, to distinguish between coherent backscatter and shadow-hiding explanations of the effect. 3) More modeling of and (with HST) searches for OH emission from the icy satellites. 4) Better characterisation of the UV reflectances with HST. 5) Possibly, 10-micron spectroscopy to look for diagnostic silicate or salt emission features (Voyager IRIS spectra are smooth but S/N is low shortward of 10 microns). 6) Better characterisation of 3-5 micron spectra to look for salts (e.g., sulfates at 4.3 microns) or other exotic components. 7) Monitoring of Europa to look for a repeat of the possible 1981 5-micron outburst. Probably not worth a dedicated program, but infrared Io monitoring programs should also look at Europa regularly, just in case. 8) Improved characterisation of the 10 micron and 20 micron eclipse cooling curves for the icy satellites. The curves are still not well understood, and the quality of existing measurements, done mostly in the 1970s, can be greatly improved upon with modern techniques. ------------------------------------------------------------------------------ OBSERVING PLANS As mentioned in our companion publication, "Io Volcano News", HST imaging of Io at all longitudes and at wavelengths between 3400 and 10,400 Angstroms, plus 1-micron eclipse observations, will be done in March this year, by Spencer, McEwen, McGrath, Sartoretti, and Johnson. So far on the flight schedule are multispectral sunlit imaging with WFPC2 at a central longitude of 230 degrees at 15:00 UT on March 5; and a 15-minute 1-micron exposure in Jupiter eclipse, starting at 4:21 UT on March 6th, to look for high-temperature volcanic emission. Many thanks to all those who have volunteered to obtain Io observations in support of the HST imaging. More observations would be welcome, particularly 1-micron sunlit photometry at the longitudes of the HST images. I will send you more details when the HST schedule is better developed. Becklin may attempt 2.1 micron observations of Io's volcanos in Jupiter eclipse from the UCLA 24" telescope (in Los Angeles), using an IR camera. Kostiuk, Kaufl, and Livengood may make 5 - 12 micron observations of Io in Jupiter eclipse from La Silla, Chile on March 4th, with an IR camera. Pogge may make 2.3 micron observations of an Io eclipse and occultation by Jupiter on Feb. 25, with the OSIRIS camera on the CTIO 60". Beth Clark will do visible photometry of Io on March 5th and 6th, with a CCD on the McDonald Observatory 36 inch. Orlando Naranjo will do visible (uBVRI) CCD photometry of Io with the 1 m. telescope at Merida, Venezuela. Carlo Blanco will do UBV photometry of Io with the 0.91 m telescope at Catania Observatory, during the first 10 days of March. John Clarke writes: We have learned that our Io FUV imaging and torus vis. imaging with WFPC 2 will be scheduled some time in May 1994. This will include near-UV imaging of the Io disk near west elongation, ranging from about 2000 A to the visible with a series of filters, FUV imaging of the Io airglow over 1300-2100 A, and visible narrow-band emission line images of the torus. The principles for Io science from the WFPC 2 team are John Trauger, Gilda Ballester, and myself. I will try to learn the exact days of our HST observations, and send these to you for distribution to the IJW Io observers. Bob Howell at WIRO (Wyoming): 5 micron speckle observations of Io, plus Jupiter eclipses and occultations. Dates: Feb. 23 - Mar. 4 UT (so the nights of 22-03 local time) Mar. 29 - Apr. 1 UT (so the nights of 28-31 local time) He hopes to have more time in April - June, but that won't be scheduled till sometime in March. Jay Goguen, with Matson and Johnson, has IRTF time April 28-29 to monitor Io's IR lightcurve. Nick Schneider, Linda Sauter, and John Spencer will use CSHELL on the IRTF on May 27 and 29 to look for 1-micron emission from neutral sulfur in Io's atmosphere. Lonne Lane has requested Mauna Kea 88" time in May for UV observations of the satellites. Spencer will again use NSFCAM on the IRTF to monitor the Io volcanism in Jupiter eclipse on June 19 and 21. Spencer will investigate the Ganymede 5770 and 6290 A absorption bands in more detail, and improve characterisation of the 0.32 - 1 micron spectral of all the Galilean satellites, from March 29-April 5, using the CCD spectrograph at Lowell. Tony Mallama and Douglas Caprette in Maryland, Donald Collins and Michal Vojticek-Lom in North Carolina, and James Park and Peter Nelson in Australia, will once again make CCD timings of eclipses of all the Galilean satellites. ------------------------------------------------------------------------- PUBLICATIONS IN (OR EMERGED FROM) THE PIPELINE This list is contains a few new articles that I've learned about. If you have an article to publicise, let me know and I'll include it here. H Hasegawa, M Takata. Predicted Brightness Variation of the Collision of Periodic Comet Shoemaker-Levy 9 with Jupiter Source Publications of the Astronomical Society of Japan 45: 6 (1993) Page(s) L73-L76 A. McEwen. SO2-rich equatorial basins and epeirogeny of Io. Submitted to Icarus Jan 1994. H Kanamori .Excitation of Jovian Normal Modes by an Impact Source Geophysical Research Letters 20: (1993) 2921-2924 DT Hall, CJ Bednar, ST Durrance, PD Feldman, MA Mcgrath, HW Moos, DF Strobel Hopkins Ultraviolet Telescope Determination of the Io Torus Electron Temperature Astrophysical Journal 420, (1994) L45-L48 -----------------------------------------------------------------------