96/97 report 008

1996/97 Mars Observation Reports -- #008 --

OAA MARS SECTION - Fortnight Report

Martian Surfaces in the Latter Half of February 1997

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

During the period from 16 Feb to 28 Feb, the apparent diameter went up from 12.1" to 13.3", and was well sufficient to watch details. The season was 079°Ls to 084°Ls, just before the summer solstice of the northern hemisphere. The latitude of the sub-earth point remained around 23°N. The phase angle decreased from 21° to 14°, and the disk became more roundish. The planet is going westwards celestially at present and observable from around 21 hours local time.

We acknowledge receipt of the observations of this period as follows:

AKUTSU, Tomio  (Ak)  Karasuyama, Tochigi, Japan
   9 CCD Images  (18, 19, 23, 25, 27 Feb)   f/66, 32cm speculum, Lynxx PC
ASADA, Hideto (Aa) Kyoto, Japan 4 CCD Images (19, 23, 24, 26 Feb) f/37, 31cm speculum, Mutoh CV-04
FALSARELLA, Nelson (NFl) Brasil 1 Drawings (26 Feb) 260× 20cm speculum
HIKI, Toshiaki (Hk) Minowa, Nagano, Japan 9 Drawing (20, 22, 24, 26 Feb) 340× 16cm speculum
ISHADOH, Hiroshi (Id) Naha, Japan 27 Drawings (19,20, 22-25, 27 Feb) 530× 31cm speculum
IWASAKI, Tohru (Iw) Morodomi, Saga, Japan 13 Drawings (17, 19, 22, 26, 27 Feb) 400× 21cm speculum
LEHMAN, David J (DLm) CA, USA 3 Drawings (16, 19, 21 Feb) 290,300× 25cm speculum
MELILLO, Frank J (FMl) NY, USA 1 Drawing (2 Feb) 310× 20cm Schmidt-Cassegrain 2 B&W Photos (21, 26 Feb) 20cm Schmi-Casse AO-2 unit TP2415 Wr21
MINAMI, Masatsugu (Mn) Otsu+/Fukui, Japan 34 Drawings (19+, 20+, 23, 24, 27, 28 Feb) 400× 20cm spec+ /400× 20cm refra*
MURAKAMI, Masami (Mk) Fujisawa, Japan 13 Drawings (20, 22, 23, 24 Feb) 370× 15cm speculum
NAKAJIMA, Takashi (Nj) Fukui, Japan 7 Drawings (23, 28 Feb) 400× 20cm refractor*
NIKOLAI, Andre (ANk) Berlin, Deutschland 7 Drawings (1, 6, 15, 22, 23, 24 Feb) 330× 10cm refractor
TEICHERT, Gerard (GTc) Hattstatt, France 1 Drawing (22 Feb) 280× 28cm Schmidt-Cassegrain
* Fukui City Observatory
We also received several good images made earlier on 8/9 Feb from Italy as follows:
QUARRA SACCO, Giovanni A (GQr) & the SGPG (A LEO, D SAROCCHI & others),
 Firenze, Italia
   7 CCD Images  (8/9 Feb)  f/24, 30cm Cass, ISIS CCD800 with Kodak KAF0400

0) : We observed in Japan the surfaces where Solis L stayed near the evening terminator through the areas where Syrtis Mj appeared on the evening side. Every observer watched M Acidalium near the CM.

1) Olympus Mons, Alba and Tempe : The region where these features lie was well observed in the previous period as reported in #186, but IWASAKI (Iw) observed again the area on 17 Feb (080°Ls): Olympus Mons was however not yet clear at ω =127°W, though Tharsis was already bright near the evening terminator. On 19 Feb (080°Ls), Iw saw Alba at ω =089°W rather on the morning side. Iw also detected the dark band which lie between Tharsis and Olympus Mons. ISHADOH (Id) tried to detect Olympus Mons on the morning side but not so successful and confusing. On 23 Feb (082°Ls) at ω =115°W, Id observed that Olympus Mons was less light than Alba. To him Alba was clear at ω =085°W, 095°W and ω =105°W together with Tempe. MINAMI (Mn) similarly observed that the morning Alba was visible roundish following Tempe on 23 Feb at ω =090°W. Alba was weaker than Tempe and not whitish maybe just sunlit. In this sense Olympus Mons and Alba are of different nature: Alba is more similar to Tempe. As to Tempe MURAKAMI (Mk) saw a round whitish core inside it on 23 Feb at ω =056°W and 068°W describing it to be impressive compared with the following reddish area. He observed it similarly on 24 Feb at ω =045°W. The B-light CCD images by AKUTSU (Ak) on 23 Feb don't however show the area light and Tempe is rather shadowy contrary to Chryse.

2) Solis Lacus : On 19 Feb Solis L was near the CM seen from Japan, and Id, Iw and Mn similarly detected the eggplant-shaped marking: Id described it at ω =072°W and 082°W, and Iw at ω =099°W and Mn watched it from ω = 080°W to 109°W. On 23 Feb it was again observed by Id as well as by NAKAJIMA (Nj) and Mn at Fukui (through O56 filter). HIKI (Hk) also observed it on 24 Feb at ω =060°W under better seeing (but temperature -7°C), and ASADA (Aa) took a CCD on 23 Feb at ω =053°W where Solis L is shown. Id clearly saw Ophir on 19 Feb at ω =082°W: According to his observations on 23 Feb, the brighter Ophir became, the nearer it came close to the evening terminator from ω =095°W to 105°W. On the same day at Fukui, Ophir-Candor was seen together with Ganges at ω =080°W, but it was covered and mixed with the bright evening haze extended from Chryse-Xanthe.

3) Hyperboreus L : M Acidalium has already been separated from the area of the north polar cap (npc) and Hyperboreus L is very dark attached to the npc though something like Iaxartes connects them. This was alluded to for the case of the previous apparition in CMO #162 p1645. This time the disk diameter is more favourable to detect the fact. To Mn, Hyperboreus L was always apparent from the beginning: On 27 Feb it was apparent already near the morning limb at ω =313°W [Note added in proof: on 4 Mar it was detected already at ω =276°W]. Iw saw separated Hyperboreus L on 22 Feb (082°Ls) at ω =072°W (App. Diam. δ=12.7"). Id also described it dark attached to the npc just like the dark fringe but didn't clearly depict the slit. He enjoyed better seeing on 25 Feb at ω =009°W, 019°W, and 029°W to observe the area. Hyperboreus L is seen in Aa's CCD images on 23 Feb at ω = 053°W and on 26 Feb at ω =022°W.

4) Evening haze and morning mist : the evening haze from the north Thymiamata to Chryse was still observed. Id chased the Chryse evening haze on 19 Feb from ω =060°W to 095°W (he is modest and writes "the neighbourhood of Thymiamata is misted light whitish" at ω =060°W). Mk observed the Chryse evening haze on 20 Feb at ω =090°W and on 22 Feb (082°Ls) at ω =072°W and 082°W, and felt it intensive on 23 Feb at ω =047°W, 056°W and ω =068°W. Iw watched it on 22 Feb at ω =053°W, 063°W and 072°W. Id depicted it clearly on 22 Feb at ω =063°W while it remained the same at ω =073°W, and furthermore he described it weaker on 23 Feb at ω =085°W. Mn at Fukui however traced it from ω =032°W, through every ten °ree observation, and observed the evening haze at Chryse-Xanthe to be light up to ω =071°W, and at ω =081°W the haze was whitish light, and at ω =090°W it violated Ganges to the Ophir-Candor area as aforementioned.
After 24 Feb (083°Ls), Syrtis Mj began to appear from the evening side, and another evening haze from Neith-Libya invaded the north Syrtis Mj (observed by Mn on 24 Feb at ω =351°W and on 27 Feb at ω =352°W), and then went to the desert region, perhaps mixed with the light Aeria which was well sunlit near the CM. On 27 Feb at ω =303°W, Mn observed a light core in Aeria. Iw described the haze to the north of S Sabaeus on 26 Feb at ω = 008°W, which might be extended to the evening haze at the north Thymiamata.
The morning mist was also intensively observed: it was very whitish bright over Thymiamata to Chryse. It extended to the north but not so hide M Acidalium: M Acidalium and S Margaritifer soon recovered.
HIKI (Hk) and Mn simultaneously observed on 20 Feb (Mn also on 19 Feb) that Tharsis was extraordinarily bright near the morning limb. Hk found it to be very bright at ω =035°W on 20 Feb (081°Ls) and Mn at ω =041°W, but at ω =050°W it turned out to be less bright. Mn observed the area again on 23 Feb (082°Ls) at ω =042°W, but it proved just usually light. Iw watched the area on 22 Feb at ω =053°W but reports that it was normal. On 23 Feb, the southern limb over Solis L was whitish bright. Hk thought that an equatorial band cloud existed from Tharsis across Chryse to the evening haze over Thymiamata. Mk observed on 24 Feb at ω =045°W that the morning limb was bright. The B-light CCD images by Ak on 23 Feb at ω = 044°W show the morning limb bright.

5) The npc :
Id0225 The npc has much retreated, and the brightest core is small. The fine dark fringe of the npc, as shown in Figure 3 at page 1873 of #177 has already been apparent, and especially from the angle we saw this period, the fine fringe was quite evident at least up to around ω =300°W. This fringe is started eastward from and connected with Hyperboreus L. Its west is not so dark to the effect that Id for example described on 20 Feb at ω = 090°W the morning side of the npc to be obscure. By chance Mn observed on 23 Feb at ω =090°W that the evening side was definite because of the presence of Hyperboreus L.
Id enjoyed good seeing condition, as mentioned before, on 25 Feb, and observed seven times from ω =359°W to ω =065°W, and judged that the atmosphere, especially at the arctic region, was clear (described at ω =046°W). He also detected a rift at ω =009°W, 019°W and 029°W, which may be identified with Chasma Boreale.
At Fukui, the east of Hyperboreus L could be observed on 24 and 25 Feb, and detected the fine dark fringe to become obscure or terminate near Olympia; that is, the evening part of the npc including Olympia was less bright. Olympia was present but our resolution was too poor to detect a fine brighter fragments in Olympia. It was also observed that even the outskirts of the dark fringe showed several lighter areas which may be the remnants of the originally bigger npc. At Fukui on 23 Feb at ω =003°W ~ 032°W and also on 24 Feb at ω =011°W a light spot was seen at Cydonia, which was sometimes blurred.

FALSARELLA (NFl) observed on 26 Feb (083°Ls) at ω =160°W where Propontis I and the morning Elysium are evident, and, as he wanted to stress (cf LtE), he nicely detected a shadowy band which ran between Tharsis and Olympus Mons (and Alba). This band is the one that appears at this season, and it was vividly observed for instance in Mar 1982 at 095°Ls in Japan. In 1995 also we first caught a germ of the band at 068°Ls (in CMO #158 p1610, the present writer reported as "It was easily realised as Olympus Mons because it was preceded by a dark band from NE to SW as in 1982; the dark band being a derivative from the aforementioned dark band as an extension of Ceraunius. ....the oblique dark band was not yet so dark at present, but we consider it will become darker as Olympus Mons and Tharsis ridge will turn out to be brighter obvious as Ls proceeds. ....".) See also #185 p2003 line23.

LEHMAN (DLm)'s drawing on 16Feb (078°Ls) was at ω =030°W, and M Acidalium stood out. The marking called the Lowell band by him may be identified with Hyperboreus L. On 21 Feb (081°Ls) he observed at ω = 340°W and saw an evening haze evading the north of the evening Syrtis Mj. Impressive is his keen observation of a light spot in Cydonia which may be the same one we observed later on 23 Feb (see above). DLm's observation time was near 10:30GMT and we can start in Japan from after 11:00GMT, and so for the time being the observations at California in the morning can readily be handed over to Japanese evening observations.

MELILLO (FMl)'s TP was on 21 Feb at ω =265°W showing Syrtis Mj. The one on 26 Feb (083°Ls) at ω =219°W clearly shows the light area of Elysium and Cebrenia in a heart-like shape. The Aetheria dark patch and Phlegra are also dark evident (cf (NB) in LtE). We should say the right-hand side of the npc is shadowed in this photo.

NIKOLAI (ANl)'s observations: On 15 Feb Elysium was at the morning side. On 23, 24 Feb Tharsis was near the evening terminator, while Olympus Mons was undetected. Depend much on filter working, but the basic one should be the Int drawing.

TEICHERT (GTc)'s drawing was made on 22 Feb at ω =145°W: Just the npc was dull, and no Tharsis. We are sorry the record of GTc' observation in the preceding issue (p2000) was wrong, and should read

TEICHERT, Gerard  (GTc)  Hattstatt, France
  4 Drawings  (6, 7, 8, 10 Feb)  280, 330× 28cm Schmidt-Cassegrain

The CCD images by QUARRA and others on 8/9 Feb (076°Ls) are excellent. We received 6 long files, and each is in a good layout, but based on their every 40 minutes observations by IR, there are 7 sets of images. IR images were taken on 8/9 Feb at ω =283°W, 293°W, 303°W, 313°W, 325°W, 336°W, and 345°W. The day belonged to our OAA Mars Watch Days, and they in Italy observed from Syrtis Mj to M Acidalium, while in Japan we were observing the region of Elysium. They seem to have met very good seeing stable for hours since the Aryn's nails are separately very evident later in spite of App. Diam. δ=11.4".

SGPG's images

We consider that the image through UV(330nm) at ω =300°W(00:30 UT) is important: Syrtis Mj is still well inside the disk, while it is thickly misted by the evening haze. This must be a kind of orographic haze since the west side of Syrtis Mj is a big slope. Because of the presence of the creeping-up haze, the colour of the north Syrtis Mj shows a tint of azure. Aeria must also be misted. As another point we consider that the CCD images show Olympia separated well from the npc.

Note added in proof : We met a very good seeing condition at Fukui on 5 Mar enough to use magnification 630× to see the beautiful image of Syrtis Mj to the early morning M Acidalium. Meanwhile ISHADOH informed us by FAX that he also had an excellent image on 6 Mar at Okinawa to catch Chasma Boreale. To be reported in the next issue.

Next issue (#187) will be published on 25 Mar, and hence contains the data from 1 Mar to 15 Mar if they will reach us by 20 Mar. The opposition day is around the corner, and please note that the second OAA Mars Watch will be coordinated from 19 Mar to 22 Mar (GMT). We invite cordially any overseas observers to join us.


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