> From jhr11@hermes.cam.ac.uk Wed Nov 27 09:24 MST 2002 Date: Wed, 27 Nov 2002 16:22:33 +0000 (GMT) From: "J.H. Rogers" Subject: Spot in Red Spot Hollow Hi all, Congrats to Ed Grafton and Clay Sherrod for picking up that ring in the Red Spot Hollow. As Prof. Reta Beebe said, it is probably an anticyclonic ring that has retrograded into the Hollow. It may be one of the common rapidly-retrograding spots (from the SEBs jetstream), like those noted by Reese and Smith (1968) and by Voyager imagery; or it may be a longer-lived oval (from the STropZ). A similar long-lived oval merged with the GRS in 1997 May-June [see our reports in Journal of the BAA, vol.107 p.333-335 Fig.6, and vol. 111 pp.186-198 Fig.7]. As shown in those images sets, the merging oval moved only slowly around the RSH and its appearance was variable as it did so. The merger took about 2 months (not 1 week), and the changing appearances suggested that white clouds and blue streaks were moving unpredictably around the remnant of the oval as it was torn apart. (Galileo took images of the GRS in the late stages of the merger, but I have not heard whether any disruption to the rotation pattern was observed.) I think it likely that the present spot was observed as a slow-moving anticyclonic ring in the STropZ in early 2002. [See the attached JUPOS chart from Hans-Joerg Mettig, and panels of images.] It was involved with a dark South Tropical Band at the time. It was 40-50 deg. p. the GRS, drifting towards the GRS at 0 to 6 degrees per month. As John McAnally pointed out, the present spot was not conspicuous before Nov.23. Prior images show no evidence that it derived from a rapidly retrograding spot on the SEBs jetstream. I think the slow-moving ring had low contrast in Sep. and Oct., as there was no dark material around it, but it can perhaps be seen as a disturbed patch moving into the RSH around Oct.17-31 [as shown in the attached image sets]. However it is really difficult to be confident that there was a single spot. Damian Peach's near-IR image on Oct.31 shows it with dramatic disturbance in the RSH. In Nov., I suggest the spot can be traced as a white spot moving slowly through that quadrant, which only became conspicuous on Nov.23 when it reached the northernmost point and swirled dark material around itself from the adjacent SEB. This scenario closely resembles what was observed in 1997. However I must admit that these interpretations are tentative and we would need sharper images to be sure what happened. I second John's call for good sharp images (and, if possible, images in violet, near-IR and methane wavebands), to follow the progress of this merger in detail. Best wishes, John. _________________________________ John H. Rogers, Ph.D. Jupiter Section Director, British Astronomical Association. _________________________________