Jupiter was quiet and no major change was observed in May. Dark arch of RS and streak extending from RS emerged by collision of SEBs jetstream spots began to decline this month. Total length of the streak was still about 140 deg. long, reaching BA. But fading of the streak progressed between about II:20 deg. and STrZ dark ring at about II:70 deg., and only reddish line as a trace of the streak and projections along SEBs remained in the end of the month. Though the streak was still distinct and prominent between dark ring and RS, dark arch surrounding south edge of RS was transforming into bridges which connected both ends of RS with SEB. It is seemed that these changes was because collisions of jetstream spot with RS decreased and what maintained the streak and arch was no longer supplied. But SEBs jetstream was still active, and jetstream spots reached RS around May 9 and 19. So, it is likely that dark arch and streak will reappear. These spots described above reached RS keeping jetstream speed of about +3 deg./day without deceleration, unlike previous group which collided with RS in February. Dark ring was at II:73.8 deg. (May 26, measured by Einaga), and was retrograding very slowly. The longitude of RS was at II:101.0 deg. (May 17, Narita's CMT).

Among prograding STBn jetstream spots, leading one reached RS around May 19. But it was not observed after that preceding RS, so it seemed to have disappeared. Next train of dark spots was approaching RS at the end of the month, but these appearances were irregular dark segment of STBn without distinct outline as spot. Though STBn had been quiet with no prominent feature following these spots, it was again darkened preceding BA over some 10 degrees in longitude, where next group will develop.

BA was elongated and light at II:315.0 deg. (May 13, Asada's CMT). It was easily seen through a small telescope, because it was surrounded by dusky markings. South of BA, there were 5 small white spots of SSTB spaced 20-30 deg. apart, and these were named A1 to A5 by Rogers of BAA. A1 had already forwarded away preceding BA, and A2 was just passing south of BA at the end of the month. The cyclonic region between A2 and A3 became somewhat darker, though it was bright and conspicuoous in April.

In northern part of EZ including NEBs edge, several prominent festoons and bluish dark plateaus were seen, and this month, small white spots called plume were observed on NEBs edge adjacent festoons. Especially, plume at about I:260 deg. on May 4 was remarkable for its typical appearance, in which a brilliant spot formed a tiny bay on NEBs edge, trailing white cloud fringing northern edge of festoon. In northern part of NEB, many barges and small white spots called porthole were observed this month, too. Two barges at around II:350 deg. out of above ones were merged around May 10, and became one elongaed dark spot.

(2) Saturn

Saturn was going down in the evening western sky, and was reducing altitude day by day. This month, we have received observations listed below. But number of images decreased as the condition for observation became poorer. Yunoki sent a set of images which summarized a change took place around Saturnian South Pole.

As described in the last report, SSTZ reddened remarkably and central part of SPR became light. Yunoki indicated that redness of SSTZ faded in southern part, and it became lighter. According to a set of images by him, the tendency was clearly seen after April, when light band was formed in the region adjoining SPR.

This month, no feature such as white spot was observed, partly because the condition became worse for observeation.

(June 9, K. Horikawa)

[Fig.1]

2005/05/17 11:45UT

I:21.1 II:139.9 25cm Refl.

Imaged by Hideto Fukui

[Fig.2]

2005/05/21 12:24UT

I:317.0 II:79.6 40cm Refl.

Imaged by Isao Miyazaki

[Fig.3]

Strip map of Jupiter on May 3

Imaged, created and measured by Hideo Einaga

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