1996/97 Mars Observation Reports -- #012 --

OAA MARS SECTION - Fortnight Report published in CMO No.190 (10 May 1997)

Martian Surfaces in the Second Half of April 1997

The Third and "Farewell" MarsWatch of the OAA/CMO was carried out from 26 to 28 April, but it was not well successful: The weather at Okinawa was bad whole three days, and no report from ISHADOH (Id) . Others also no more than two nights: For example IWASAKI (Iw) made observations on the 26th and the 28th (rainy on 27th) , while MURAKAMI (Mk) on the 26 and 27th. Iw on 26 Apr observed every forty minutes from 10:50 GMT (at ω =140°W) to 14:10 GMT(at ω =189°W) . At Fukui, the 26th day was in good seeing condition, but we were forced to print and bind CMO #189 in the evening, and hence we were not able to carry out the 40 minute observations. NISHITA (Ns) however waited Propontis I to come up and shot it as well as Olympus Mons by a CCD camera successfully. On 27 Apr NAKAJIMA (Nj) and Mn made observations every forty minutes from 10:10 to 14:10 GMT , but seeing was rather poor.

We received with thanks the following observations contributed to the CMO this time:

AKUTSU, Tomio (Ak) Karasuyama, Tochigi, Japan
 19 CCD Images(12, 13, 19, 22, 26, 27, 29 Apr)  f/66× 32cm speculum, Lynxx PC

CAVE, Thomas R (TCv) CA, USA
  5 Drawings(8, 16, 25, 28, 30 Apr)  280,290,400,550× 32cm speculum

GROSS, Horst(HGr)  Hagen, Deutschland
  2 Drawings(17, 21 Apr)  250× 25cm Schiefspiegler

HIGA, Yasunobu(Hg)  Naha, Japan 
  9 CCD Images (prints)  (20 Mar; 7, 20, 21 Apr)  25cm spec, Sony DV Camera VX1000 
 38 Video Images(20, 24, 28 Mar; 7, 11, 12, 16~21, 30 Apr)  25cm spec, VX1000

HIKI, Toshiaki(Hk)  Minowa, Nagano, Japan
  6 Drawings(16, 26, 27 Apr) 340× 16cm speculum 

ISHADOH, Hiroshi(Id) Naha, Japan
  8 Drawings(17, 19, 20, 21, 30 Apr) 530× 31cm speculum

IWASAKI, Tohru(Iw)  Kita-Kyushu, Japan
 13 Drawings(26, 28, 29 Apr) 400× 21cm speculum

MELILLO, Frank J (FMl)  N‚x, USA
  7 B&W Photos (3, 5, 8, 11, 15, 16 Apr)  20cm Schmi-Cass AO-2 TP Wr47 & Wr21 

MINAMI, Masatsugu(Mn) Fukui / Otsu+, Japan
 62 Drawings(16+, 17+, 19+ , 20, 23$Apr)  420× 20cm spec+/400, 480× 20cm refra* 

MURAKAMI, Masami(Mk) Fujisawa, Japan
 22 Drawings(17, 22, 23, 24, 26, 27$, 29$ Apr) 370× 15cm spec/400× 20cm refr$

NAKAJIMA, Takashi (Nj) Fukui, Japan
 25 Drawings(19, 20, 24, 26~29 Apr)  400, 480× 20cm refractor*

NARITA, Hiroshi(Nr) Kawasaki, Japan
 32 Drawings(17, 19, 22, 23, 25, 27, 29 Apr)  400× 20cm refractor$
   8 Colour Photos(4, 8, 23 Feb; 4 Mar; 10, 12, 19, 22Apr) f/280× 20cm refr$ G400

NIKOLAI, Andre(ANk)  Berlin, Deutschland
   1 Set of Drawings (17 Apr)  375× 15cm refractor at the WFS, Berlin

NISHITA, Noriaki(Ns)  Fukui, Japan
   2 CCD Images(26 Apr)  20cm refractor*,Mutoh CV-04

SIEGEL, Elisabeth(ESg) Malling, Danmark
   1 Drawing(18 Apr)  270× 20cm Schmidt-Cassegrain

TEICHERT, Gerard(GTc) Hattstatt, France
   5 Drawings(1, 6~9 Apr)  280, 310,330,350× 28cm Schmidt-Cassegrain

TROIANI, Daniel M (DTr)  IL, USA
   6 Drawings(22, 23, 26~29 Apr)  520× 44cm speculum 

                              * Fukui City Observatory
                              $ Tama AstroObservatory

CAVE, Vanessa (VCv)  CA, USA
  2 Drawings(21, 25 Mar)  400× 32cm speculum

GRAHAM, David L(DGh) North Yorkshire, UK
  8 Drawings(3, 10, 19, 24, 28 Mar; 9, 15 Apr)  220,285× 15cm refr/200,285× 40cm spec

OKANO, Kunihiko (Ok)  Tokyo, Japan
  1 CCD Image(20 Mar)  31cm speculum,ST-5, O56

ASADA, Hideto(Aa) Kyoto, Japan
   8 CCD Images(16,17,19,20,25,26,27,29 Apr) f/37× 31cm speculum, Mutoh CV-04

1) Olympus Mons :
This period Olympus Mons ( ω =133°W) became visible from the angle ω =150°W, and well seen at ω =160°W, though it didn't particularly show any white tinge.
IWASAKI (Iw) saw it vaguely on 26 Apr at ω =150°W, and
MURAKAMI (Mk) checked it on 26 Apr at ω =176°W, and
HIKI(Hk) on 26 Apr at ω =179°W and on 27 Apr at ω =172°W.
At Fukui, the present writer (Mn) on 25 Apr (109°Ls, phase angle ι =27°) noticed it at ω =149°W, and clearly saw it light bounded by a dark ring at ω =169°W.

Olympus Mons thus was quite at the left-hand side (seen from the NH) , but its local time was just after the noon
[ roughly (169-133+(90-27) ) /15=6.6 is the hour separated from the dawn ] .
On the same day at ω =188°W, the bright spot ringed was clearer. On 26 Apr (110°Ls, phase angle ι =28°)
Mn and Nj met more good images at ω =184°W and at ω =189°W respectively. Compared with the preceding white Ascraeus Mons, Olympus Mons was off-white, but considerably bright. The local time was about 1:30pm. On the same day, it came close to the evening limb at ω =213°W: the local time was however just about 3:30pm. Among our observations, the angles ω =219°W on 20 Apr by Mn and ω =218°W on 26 Apr by Nj were the moments when Olympus Mons was watched roundish latest near the following limb, but even these angles show that the local time was just about 4:00pm.
AKUTSU (Ak) shows by a B-light CCD the shining Olympus Mons at the evening limb on 22 Apr at ω =218°W.
ISHADOH (Id) saw the edge-on Olympus Mons at ω =222°W on 21 Apr.
HIGA (Hg) also at Okinawa took a Video image at the same time on the same day and revealed the shining Olympus Mons on the egde. But the local time was not so different.

Consequently we can safely say that Olympus Mons was still very active in the afternoon or in the evening as before. In fact, as was analysed in #188 p2046, the afternoon activity of Olympus Mons this season begins at about 2:30pm local time, and the so-called cotton-ball can be visible at about 4:30pm, and hence the present aspect is not contradictory to the general aspect of the very active state. The above also proves we can no longer meet the glorious cloudy figure of Olympus Mons at 4:30pm hereafter this apparition.

2) Alba :
Roundish Alba Patera ( ω =110°W) was caught much earlier than Olympus Mons. This is not due to the white-cloud activity, but perhaps because of the reflection effect.
At Fukui we first caught it on 25 Apr at ω =139°W at 10:10 GMT(19:10JST) . On 26 Apr it was seen clearly at ω = 118°W (9:20 GMTtwilight) and on 27 Apr (110°Ls, phase angle=28°) at ω =121°W. The local time of Alba was about 10:30am.
MURAKAMI (Mk) saw it earlier at ω =113°W on 29 Apr together with the preceding Tempe.
Iw observed it on 26 Apr at ω =140°W,
Nj on 27 Apr at ω =126°W and Id on 30 Apr at ω =130°W.

Now let us assume that Alba Patera is a plateau having a level surface, and then, since the reflection angle is (28/2) ° if phase angle=28°, Alba must shine most at the angle ω =124°W because 110+(28/2)=124. This value is not so different to those reported above, and hence the Alba is considered to have been very evident because of the reflection of sunlight. Alba was observed also further to the limb side, but never became whitish (very different from the presnt aspect of Tharsis) .

3) A Dark Band in Arcadia :
In an area between Olympus Mons and Propontis I, a dark band was observed in NS direction for example by Nj on 24 Apr at ω = 168°W and by Mn on 24 Apr at ω =182°W and 26 Apr at ω =167°W. It must be moderate-densely reddish. In connection with this, Azania was rather light surrounding Propontis I (by Mn on 20 Apr at ω =189°W) .

4) Mareotis Lacus ? :
A conspicuous but complex broad dark band runs eastward from Nilokeras, which must be seasonal as similarly observed in 1982 while not prominent in another season when Tractus Albus is obvious as a light broad belt. The dark band includes inside a darker and larger "densely reddish" area as a large extension of Mareotis L (or classical Ascraeus L) as shown in the Figure in #188 p 2050. This band goes upward between Tharsis and Olympus Mons to a shadowy area which lies far to the west of Phasis on one hand and eastward weakly to Propontis I on the other.

5) Elysium Mons :
As a continuation of our observations reported in the preceding issue, Id detected a white Elysium Mons on 17 Apr (105°Ls) at ω =258°W ( Elysium Mons at about 1:30pm local time ) . He also observed Elysium on 19 Apr at ω =223°W near the CM but reported that it was never whitish.
Elysium (as well as Cebrenia) was shot clearly by Ak by R-light CCD on 19 Apr at ω =211°W and on 22 Apr at ω =200°W, ω =215°W, ω = 235°W et al.
The Video images by HIGA (Hg) on 21 Apr show interestingly the area of Elysium and Cebrenia. Especially the B-light print at ω = 210°W clearly revels a cloud stream from Elysium Mons westward to the outside (which could be seen by naked eyes also) . Incidentally Hg's video images go as follows on 21 Apr at ω =193°W, 202°W, 212°W, 222°W, 232°W, and 241°W available to check the change of the Elysium area.

6) Syrtis Major, Morning :

The phase angle was 25° on 20 Apr, but Syrtis Mj was seen on the morning terminator at ω =228°W (by Mn by use of O56 filter) . Syrtis Mj was beneath the mist in the morning.
Id detected a core of the mist was over the middle of Syrtis Mj on 17 Apr at ω =258°W. He also observed that the following Aeria was light on 20 Apr at ω =250°W.
The Video images by Hg on 17 Apr especially at ω =246°W, 255°W show Syrtis Mj covered by a thick mist as observed by Id.
Incidentally Hg chased Syrtis Mj successively at ω =246°W, ω =255°W, ω =265°W, ω =275°W, ω =285°W, ω =295°W and ω =304°W.
17 Apr 1997 (105°LS)
at ω=258°
by H ISHADOH (Id)

7) Olympia :
Olympia was frequently observed this period by many observers from the CM to the evening, and also in the morning. Hg's Video images also show it frequently.
Id caught it in the evening clearly on 17 Apr (105°Ls) from ω =258°W and 270°W, and described it adjacent to the SE neighbourhood of the npc on 19 Apr at ω =223°W and 241°W, and further detected it to the south of the npc on 21 Apr at ω =212°W and 222°W. On 30 Apr at ω =130°W, he saw it on the morning side in a shape of tongue.
Nj also observed Olympia to the south of the npc from ω =194°W - ω = 233°W on 19 Apr. Similarly on 20 Apr from ω =194°W and 214°W et al. On 26 Apr at ω =172°W he saw it to the south-west of the npc, and also on 29 Apr at ω =115°W in the morning.
HIKI (Hk) observed Olympia lying largely at the morning side on 26 Apr from ω =179°W.
Mk also detected Olympia appearing on the morning side on 29 Apr at ω =113°W.
The present writer (Mn) made similar observations.

However it was difficult to check both ends of Olympia. The east end appeared to come to the CM around from ω =160°W: It was a good view of Olympia to watch it around from ω = 150°. On 20 Apr we could see it overlie the npc from the south at ω = 238°W, but it looked too complexed to describe.
Ierne was also seen on 25 Apr from ω =139°W and 149°W and on 27 Apr from ω =131°W and 141°W to the east-south of the npc.

From America :
Tom CAVE (TCv) took the drawings on 8 Apr (100°Ls) at ω =202°W, where Elysium, whitish, was near the CM, on 16 Apr at ω =138°W, where Olympus Mons and Alba were near the CM, and Olympia was detected though too small and confusion around Propontis I, on 25 Apr at ω =043°W, on 28 Apr at ω =023°W and on 30 Apr at ω =340°W.
MELILLO (FMl) 's out-of-fashioned TP but true blue photos are all interesting:
Notes by FMl on the Wr47 photo on 3 Apr at ω =256°W include "Equatorial Band Clouds were seen very apparently across the disk" showing a mist over Syrtis Mj. The area of Elysium Mons is also light. Another image by Wr21 at ω =258°W shows Syrtis Mj large.
The third at ω =260°W by VG -1 (Scott UV) shows a faint Hellas. The EBC is also taken on 5 Apr at ω = 230°W by W48 and at ω =235°W by VG-1.
Elysium Mons is not visible. On 8 Apr by Wr47 at ω =195°W, a smaller white patch at the evening limb, and a larger dull mist at the morning side. The image by Wr21 at ω =203°W shows Elysium light accompanied by the Aetheria dark patch.
On 11 Apr (103°Ls) at ω =146°W (thru VG-1) Olympus Mons does not show up, while seen vaguely at ω =168°W (thru Wr47) : The local time was about 1:00pm and hence it can be considered that a dull mist over Olympus Mons still appears soon after noon still this period.
On 15 Apr by Wr47 at ω =140°W, Candor-Tharsis light at the evening side.
On 16 Apr at ω =113°W (thru Wr47) , the area of Tharsis to Olympus Mons is light before noon (FMl writes "surprisingly") it being so bright that there is "a gap in EBC". The phenomenon was checked already on the CCD images by QUARRA (GQr) and his colleagues on 8 Apr (reported in #189) . Visually it was observed at the end of March (cf #188 p2049) . The activity of Tharsis in the morning including EBC began also to be observed from 20 Feb (081°Ls) by Hk and Mn (cf #186 p2019&2020) .
TROIANI (DTr) made drawings on 22 Apr at ω =045°W, 23 Apr at ω = 031°W, 26 Apr at ω =018°W, 27 Apr at ω =341°W, 28 Apr at ω =351°W and 29Apr at ω =339°W by use of Wr25, Wr47, and Wr80A filters.

From Europe :
GROSS (HGr) obtained the drawings on 17 Apr at ω =353°W and on 21 Apr (107°Ls) at ω =302°W: In the former an evening Hellas is seen and in the latter it was bright near the CM. A light area in Aeria.
NIKOLAI (ANk) observed on 17 Apr by use of B+W081, 041, and 480 filters. By B+W041(orange) at ω =349°W, he detected Olympia as well as Rima Borealis (not Chasma Boreale) .
SIEGEL(ESg) made a drawing on 18 Apr at ω =001°W, where the morning Tempe was particularly bright and had a core.