96/97 report 015

1996/97 Mars Observation Reports -- #015--

OAA MARS SECTION - Monthly Report published in CMO No 193 (25 July 1997)

Martian Sufaces Observed from 16 June to 15 July 1997

- - - by Masatsugu MINAMI, Director of the OAA Mars Section ---

The present report deals with the observations of Mars during the period from 16 June (134degsLs) to 15 July (148degsLs). The apparent diameter was 8.2" on 16 June, but went down to 6.9" on 15 July. The central latitude stayed near 26° N-25° N so that the north polar cap (npc) was always visible. The phase angle attained a maximum at 41° during the period.

Around 20 June, the declination of Mars came across the celestial equator and went down to the southern hemisphere, and hence its altitude became rapidly lower, causing a difficulty in observing the planet in the western sky from our Hemisphere. Furthermore we met two Typhoons in June across the main island (extraordinarily - usually Typhoons come in September) and we had a heavy rainy front from 6 to 13 July.

During the period, we heard the news that the Mars PathFinder safely landed on 4 July (5 July JST). Before that, the HST found a dust storm at Valles Marineris (see below).

We received with thanks the following observations contributed to the CMO this time:
ISHADOH, Hiroshi (Id)  Naha, Okinawa, Japan
      2 Drawings  (13, 14 July)  530×  31cm speculum

IWASAKI, Tohru  (Iw)  Kita-Kyushu, Japan
     16 Drawings  (17, 23, 26, 29, 30 June; 2-5 July)  400×  21cm speculum

MELILLO, Frank J  (FMl)   NY, USA
      6 B&W Photos (5, 9, 10, 17, 24, 30 June) 20cm Schmi-Cass AO-2 on TP thru Wr47 

MINAMI, Masatsugu  (Mn)  Fukui / Otsu+, Shiga, Japan
     31 Drawings (17, 23, 24, 29+ , 30+ June; 1, 4, 6, 8+, 13+, 14+ July)
         480,600×  20cm refra (Fukui City Observatory) / 420×  20cm spec+ 

MURAKAMI, Masami  (Mk)   Fujisawa, Kanagawa, Japan
      4 Drawings  (27*, 29 June; 6 July)  370×  15cm speculum/ 315×  10cm refractor*

NARITA, Hiroshi  (Nr)   Kawasaki, Japan
     22 Drawings  (16, 23, 24, 26, 27, 30 June; 1, 2, 7 July)  400×  20cm refractor

NIKOLAI, Andre  (ANk)  Berlin, Deutschland
      3 Drawings   (25 June; 7, 13 July)   225,375×  15cm refraktor an der WFS

TEICHERT, Gerard  (GTc)  Hattstatt, France
      2 Drawings  (15, 18 June) 280,310,330,390×  28cm Schmidt-Cassegrain

TROIANI, Daniel M  (DTr)   IL, USA
      2 Drawings  (2 July)  520×  44cm speculum

We acknowledge also receipt of the reports from the following observers who contributed the observations obtained earlier:

CAVE, Thomas R  (TCv)  CA, USA
      1 Drawing  (16 May)   550×  32cm speculum

FALSARELLA, Nelson  (NFl)   Brasil
      1 CCD Image  (20 April)   32cm speculum

ISHIBASHI, Tsutomu  (Is)  Sgamihara, Kanagawa, Japan
      5 B&W photos  (23, 30 Dec; 11 Jan; 8, 12 Feb)  31cm speculum HIE, 400Prest, TP
      3 Colour photos  (27 Apr; 28, 30 May)  31cm speculum  Fujichrome 400 Provia

RICHRDS, Thomas  (TRc)  Victoria, Australia
      1 Drawing  (31 May)   250×  15cm Maksutov

ROBINSON, Robert L  (RRb)  WV, USA
      1 Drawing  (30 April)   330,490×  25cm speculum

SCHMUDE, Richard W, Jr  (RSc)  GA, USA
      1 Drawing  (14 June)     570×  51cm speculum

WARD, Don  (DWd)  Victoria, Australia
      6 Drawings  (10, 11, 13, 18, 21 Apr; 4 May)   150×  15cm speculum

WARELL, Johan  (JWr)  Uppsala, Sweden
     12 Drawings  (21, 22, 26, 27, 29, 31 May; 1, 3, 5, 7, 11, 12 June) 
         330×  16cm refractor (Uppsala University Astronomical Observatory)
WHITBY, Samuel R  (SWb)  Hopewell, VA, USA
      2 Drawings  (11, 13 June)     310×  15cm speculum

From Japan
We were able to see M Acidalium in mid-June, and through the areas of Syrtis Mj and Elysium, we at the end of the period could observe up to around ω=120° W.

17 June (134° Ls), at Fukui the observation by Mn started from twilight at ω=005° W, and possible until ω=044° W every forty minutes. The preceding limb was bright and the Noachis to the southern limb was also light. The morning Chryse and Xanthe were dull misty and Tempe also dull whitish. Hyperboreus L was dark and the npc was clear, showing a tint of bluish white. IWASAKI (Iw) also observed at ω=022° W and 031° W, and detected S Sabaeus and M Acidalium properly but indifferent to the misty matters.

23 June, Syrtis Mj came into sight in the afternoon. Mn observed from ω= 314° W to ω=353° W, and Iw at ω=324° W and 342° W. The phase angle was 40° , but S Meridiani and M Acidalium became visible from ω= 330° W, and they were definite at ω=343° W. At the same time the morning Chryse looked misty white. Hellas was very bright until ω=334° W, but at ω=343° W it became quite blurred. At this time the npc was much brighter than Hellas. The afternoon cloud at Libya seemed to creep up Syrtis Mj and protruded to Aeria(ω=334° W to 353° W). The morning M Acidalium is separated from the npc by a hazy matter.

24 June, seeing was moderate at Fukui, Mn observed from ω=297° W (twilight) to ω=336° W: At ω=297° W, the brightest part of the npc looked quite roundish and definite, and Olympia was also observed to the east. The preceding limb cloud was connected with the one over Libya near noon. N Alcyonius was visible. At ω=307° W, Utopia showed a brownish tinge, while Syrtis Mj was rather black from this angle. Hellas was as bright as the npc [NARITA (Nr) noted at the same angle that Hellas was brighter than npc]. At ω=317° W, Hellas was milky white, while the npc blue white. At ω=326° W, Libya became brighter, while Hellas duller.

26 June, Iw observed at ω=305° W and 314° W: In the former Hellas was whitish as if relieved against the disk, and in the latter most of S Sabaeus was apparent. The npc shined, he described.

27 June, MURAKAMI (Mk) observed at ω=273° W and 283° W, but could not detect the faint Syrtis Mj at dawn. Nr saw it at ω=278° W.

29 June, at the ω=254° W observation by Mn , Syrtis Mj was under the morning mist, but it was detected faintly at ω=264° W. Iw also saw it at ω=266° W. Iw considered that at ω=286° W Syrtis Mj gained its intrinsic intensity (far out of the morning mist). The day the preceding limb was bright. Hellas, as observed by Iw, became bright from ω=276° W. At ω=283° W it was prominent (by Mn). Mk observed only at ω=251° W.

30 June, Hellas became visible from ω=266° W by Iw, and from ω= 269° W by Mn. Syrtis Mj was already shadowed.

1 July, Mn observed that at ω=230° W the marking of Cerberus and Styx (maybe plus Phlegra) was well fat and dark, and Elysium was evident as a light belt to the direction of SN. Eridania was light, and the morning mist preceding Syrtis Mj (not yet) was thick. The dark band at Gyndes was broad and the area of the npc was largely light. At ω=240° W, a tip of Syrtis Mj was seen. Styx was still dark.

2 July, Iw observed that at ω=247° W Elysium looked whitish light. Syrtis Mj was still obscure.

3 July, Iw pointed out that at ω=227° W Cerberus-Phlegra was "considerably" dark.

4 July, atω=218° W, Iw observed that Elysium as light as the surrounding desert. Mn at ω=230° W, but seeing poor.

5 July, Iw observed that Elysium was not light at ω=208° W and 218° W.

6 July, Mk observed at ω=189° W, and Mn at ω=201° W and 218° W, seeing was poor at Fukui though Styx was seen. The preceding limb light.

After that Mn watched on 8 July at ω=145° W, on 13 July at ω=121° W through 141° W, and on 14 July at ω=119° W and tried to observe the dark band at Ascraeus L but in vain due to poor and unstable weather condition. The last observation was aimed to see also the afternoon limb to watch the HST dust site, but the limb was not particularly bright. ISHADOH observed on 13 July at ω=143° W and on 14 July (147° Ls) at ω= 126° W: The preceding limb light, and caught the dark line passing Ascraeus L. The npc small but light.

Overseas Observations

MELILLO (FMl)'s Wr47 TP photos are of all small images, and cannot be read as are stated in the Observing Notes: He took on 17 July at ω=243° W (FMl believes a faint EBC in it), on 24 June at ω= 175° W (he admits that the image dull without any white clouds) and on 30 June at ω=121° W (which shows also nothing; even the npc. FMl came to know that HST took a picture of a dust storm when he was writing the Notes, and hence he seems to connect the dull aspect of his images with the dust storm. But the HST image on 27 June was full of white clouds and the npc was evident, that is, the dust storm was not global). FMl also took on 5 June at ω=358° W, on 9 June at ω=331° W and at 10 June at ω=310° W; the last showing the bright Hellas and the npc.

NIKOLAI (ANk) made drawings: On 25 June at ω=081° W where the preceding limb and the npc bright and M Acidalium (Int, but B+W081 giving not so different image). On 7 July at ω=312° W, Syrtis Mj looked natural while Hellas was rather weak. On 12 July at ω=259° W, ANk caught the Aetheria dark patch. Syrtis Mj was not yet. ANk's drawing method looks beautiful and he obtained a total of 93 drawings this season (the number differs from ours in this journal because of different counting).

TEICHERT (GTc) observed on 18 June at ω=144° W, where the npc definite. On 15 June at ω=173° W, a dark spot was seen in the morning side.

TROIANI (DTr) observed on 2 July (LtE) at ω=107° W to observe the dust storm detected by the HST on 27 June (LtE): The red light observations show two bright areas near the p-limb.

HST Dust Cloud on 27 June

As informed by Jim BELL (LtE), the HST Wide Field Planetary Camera 2 took pictures at the end of June to precede the landing of the Mars PathFinder on 4 July, and discovered a streak of a dust storm inside Valles Marineris on 27 June (139° Ls). Readily the Internet of the STScI Web site provided the image compared with the normal image on 17 May: Apparently Valles Marineris on 27 June was filled with the dust cloud from the Tithonius L to Eos: Especially the eastern part near Hydraotes Chaos was thicker and looked to expand to the classical Chryse. The news was interpreted and forwarded in Japanese by Mk to several active observers in Japan by CMO E-mail/Fax Notice #008. It was anticipated that the region would come into sight from 7 July in Japan. In mid-July another Internet STScI pages were uploaded in which a new image on 9 July (145° Ls) as well as on 10, 11 July was compared with the image on 27 June. The dust looked already dispersed, just thinly floating at Chryse. (See the Click column below.) The landing of the PathFinder on 4 July (5 July JST) was successful as widely pressed and telecasted.

Some observers argued their observations without checking the HST Image on 27 June. IAU Circular # 6693 (dated 5 July) reported that M GASKELL at Nebraska observed a dust activity at Ascraeus- Ceraunius near the p-limb on 26 June, and successively on 28, 29, 30 June and 1 July (by use of 47520cm spec). Strangely however the HST image on 27 June shows that the Ceraunius area was free from the yellow cloud (just white hazed). R McKIM commented in the Circular that in 1935 and 1978 dust activities were observed at the area of Ceraunius at "the identical season": The 1978 observation must have not however been made ground-basically since the season 139° Ls was attained when the apparent diameter was only around 4.2 arcsecs (while in 1935, the diameter was about 11.3 arcsecs).

We- Further- Received

CAVE (TCv) observed on 16 May (118° Ls) at ω=204° W where classical Elysium was evident. Propontis I was isolated. Mists seen at the both limbs.

FALSARELLA (NFl)' s CCD image was on 20 Apr at 0:08GMT: M Acidalium is at the centre with other major markings, but the image is unstable.

ISHIBASHI (Is) 's B&W photos were taken 23 Dec at ω=296° W, 30 Dec at ω=256° W, 11 Jan at ω=138° W, 8 Feb at ω=235° W and 12 Feb at ω=173° W (timed by the Red photos). On 11 Jan (063° Ls), the npc is more definite in blue. Tharsis seen at the evening terminator (app diam δ=8.8 "). The EBC is not clear. Colour photos were taken 24 Apr at ω=162° W, 28 May at ω=217° W and 30 May at ω=193° W. The images on 30 May (125° Ls, app diam δ=9.2") are excellent (2 and 3 sec exps): Propontis I is isolated evident, and Styx also dark. The morning Elysium is covered by a whitish mist. The preceding limb is bright (Tharsis). The npc is definite. The image on 24 Apr is also moderate.

RICHARDS (TRc)' s drawing on 31 Mar at ω=043° W was kindly sent by B ADCOCK, Victoria, Australia to whom we are thankful. M Acidalium was vaguely seen.

ROBINSON (RRb) made a drawing on 30 Apr (111° Ls) at ω=330° W, where Hellas was as bright as the npc. Syrtis Mj evident.

SCHMUDE (RSc) took a drawing on 14 June (cf LtE) at around ω=270° W: the defect of illumination is at the left-hand side, and we cannot find Syrtis Mj. The disk is never "cloudy" (cf LtE).

WARD (TWd)'s drawings were also sent by B ADCOCK: 10 Apr at ω=308° W where Syrtis Mj was main, and Hellas bright even without a blue filter. 11 Apr atω=303° W. 13 Apr at ω=273° W, where the Aetheria dark patch was evident while Hellas obscure. 18 Apr at 12:23GMT, where Elysium light. On 21 Apr at ω=197° W. 4 May at ω=082° W where M Acidalium near the p limb.

WARELL (JWr) made observations on: 21 May at ω=068° W where a weak EBC was seen and Hyperboreus L evident. 22 May at ω=051° W. 26 May at ω= 009° W where Tempe was morning misty. 27 May at ω=015° W where Noachis was light near the p limb. 29 May at ω=346° W, where Hellas visible. 31 May at ω=327° W where a morning mist protruded to the north of S Meridiani. 1 June at ω=316° W, where Hellas was creamy white while the npc blue white. JWr's S Sabaeus is separated from M Serpentis. 3 June at ω =301° W. 5 June at ω=279° W. 7 June at ω=258° W where Syrtis Mj was misted and weak, Hellas bright. 11 June at ω=224° W where Cerberus- Styx looked dark. 12 June at ω=219° W when the apparent diameter was 8.3".

WHITBY (SWb) made observations on 11 June at ω=288° W and on 13 June at ω=270° W: The former shows a bright Hellas while Syrtis Mj was weak, weaker in blue. In the latter, seeing being 8/10, Syrtis Mj was weak but visible through Wr21 (while through Wr80A invisible). Hellas was not observable. To SWb, the npc was rather obscure: He detected a contour of the npc in the former but in the latter the npc looked blurred. The contour of the npc appears indefinite to the north of Utopia in the late summer.

Next issue will be published on 25 August.

Reports will be acknowledged if air-mailed to M MINAMI at Mikuni
(ask the mail-address through vzv03210@niftyserve.or.jp ) .

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