96/97 report 011

1996/97 Mars Observation Reports -- #011 --

OAA MARS SECTION - Fortnight Report published in CMO No 189(25 April 1997)

Martian Surfaces in the First Half of April 1997

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

The red planet is now on the way off orbitally from the opposition point (most approached on 20 Mar) and the apparent diameter was 13.9" on 1 Apr and further went down to 12.9" on 15 Apr. The phase angle augmented from 12° to 22° during the period. The season proceeded from 098° Ls to 105° Ls. The central latitude was around 24° N.
The planet still moved regressively (until 29 April) and it shined higher at meridian.

We acknowledge receipt of the following observations contributed to the CMO this time:

CAVE, Thomas R  (TCv)  CA, USA
    1 Drawing  (1 Apr)   400, 660× 32cm speculum

DIJON, Jean   (JDj)  Champagnier, France
   10 CCD Images (9~12, 16, 17, 22/23, 31 Mar; 1, 2 Apr) 31cm spec with KAF400

FALSARELLA, Nelson  (NFl)  Brasil
   12 Drawings  (18, 20, 23 ~26, 28, 30 Mar; 2 ~5 Apr) 260× 20cm spec
    2 CCD Images (3/4, 4/5 Apr) 20cm spec with AVA ASTROVID 400

GROSS, Horst   (HGr)   Hagen, Deutschland
    2 Drawings  (7, 8 Apr)     250× 25cm Schiefspiegler

HIKI, Toshiaki  (Hk)   Minowa, Nagano, Japan
    3 Drawings  (1, 12 Apr)  340× 16cm speculum
ISHADOH, Hiroshi  (Id)  Naha, Japan
    5 Drawings  (12 Apr)  530× 31cm speculum

MINAMI, Masatsugu  (Mn)  Fukui /  Otsu+, Japan
   55 Drawings  (1, 9 ~13, 14+, 15+  Apr) 400, 480, 630× 20cm refra* /420× 20cm spec+
MURAKAMI, Masami  (Mk)   Fujisawa, Japan
    9 Drawings  (8, 10, 12, 13 Apr)    370× 15cm speculum

NAKAJIMA, Morimasa  (Nk)  Yokohama, Japan
    3 Drawings  (10 Apr)    320× 20cm speculum

NAKAJIMA, Takashi  (Nj)   Fukui, Japan
   14 Drawings  (1, 10, 12, 15 Apr)    400, 480× 20cm refractor*

NAKANO, Yuhkichi  (Nn)  Oh-ita, Japan
    7 Drawings  (1, 7, 10 Apr)    420× 20cm speculum 

NARITA, Hiroshi  (Nr)  Kawasaki, Japan
   19 Drawings  (1, 4, 10, 12, 13, 14 Apr)  400× 20cm refractor

OHBA, Yoshio  (Oh)   Yamagata, Japan
    7 Drawings  (1, 10, 13, 15 Apr)   210, 270, 320× 20cm speculum

QUARRA SACCO, Giovanni A (GQr) 
             & the SGPG (A LEO, Del ZANNA & others)  Firenze, Italia
    2 CCD Images  (8 Apr)  f/24× 30cm Cass, ISIS CCD800 with Kodak KAF0400

SIEGEL, Elisabeth  (ESg)  Malling, Danmark
    3 Drawings  (4, 6, 15 Apr)  270× 20cm Schmidt-Cassegrain

    1 CCD Image  (14 Apr)  13cm refractor  VAV 505E Video Camera

TEICHERT, Gerard  (GTc)  Hattstatt, France
    7 Drawings  (1, 6 ~10, 13 Apr)  280,310,330,350× 28cm Schmidt-Cassegrain

TROIANI, Daniel M   (DTr)  IL, USA
    6 Drawings  (1, 2, 8, 9, 14, 15 Apr)  520× 44cm speculum
WARELL, Johan  (JWr)  Uppsala, Sweden
    5 Drawings  (31 Mar; 4, 7, 12, 15 Apr )  330, 400× 16cm refr, 290× 45cm spec

                                             * Fukui City Observatory

As the observations obtained earlier, we received with thanks the following
NIKOLAI, Andre  (ANk)  Berlin, Deutschland
  2 Drawings  (22, 29 Mar)   330× 10cm refractor

SCHMUDE, Richard W, Jr (RSc)  GA, USA
  3 Drawings  (21, 23, 27 Mar)     570× 51cm spec, 380× 25cm spec
  3 Colour Photos  (16, 23, 27 Mar)      51cm spec  ISO100

We also received as follows:
ADACHI, Makoto  (Ad)   Otsu, Japan
  8 Drawings  (19, 27 Mar; 1 Apr)  340× 20cm refr, 360,500× 31cm spec

ASADA, Hideto  (Aa)   Kyoto, Japan
  8 CCD Images  (1, 10, 12, 13 Apr)  f/37× 31cm speculum, Mutoh CV-04 

0) The beginning of this April was cruel to us: the rainy days continued more than one week, and the observation rate much decreased in Japan. According to ISHADOH (Id), at Naha, Okinawa, they had only three possible nights, but Id spent two nights in observing the Hale-Bopp Comet in a remote place, and no more than one night was available to Mars (on 12 Apr). At Fukui we however had finer conditions from 9 April. During the period the regions from M Acidalium to the morning Syrtis Major faced toward us.

1) Hellas : As said, the weather improved from 9 Apr (102° Ls), and the planet readily showed that Hellas was very whitish bright on the afternoon side: On 10 Apr, NARITA (Nr) observed it at ω=281° W (and thereafter), NAKANO (Nn) at ω=291° W, M NAKAJIMA (Nk) at ω=294° W (and thereafter), OHBA (Oh) at ω=300° W. On 12 Apr, Id observed Hellas from ω=295° W, and HIKI (Hk) from ω=307° W. MURAKAMI (Mk) saw the brilliant Hellas at ω= 289° W on 13 Apr, Sunday (Mk works weekdays up until midnight).
The fact was anticipated from the work by SMITH & SMITH (cf CMO #134 p1251), and the restricted experiences by the present writer in 1980, 1982 and 1984 showed really that Hellas turned out to shine around from 093° Ls, 105° Ls and 100° Ls respectively (dependent much on the chance). This time, we are able to refer to the overseas observations and hence we can date back to somewhat earlier witness: For example on 17 Mar (092° Ls) at ω=309° W, TEICHERT (GTc) observed the bright Hellas (cf #188 p2055), and SCHMUDE (RSc) on 23 Mar (094° Ls) (cf p2056 and below), MELILLO (FMl) (cf p2054) and TROIANI (DTr) (cf p2055) on 24 Mar (095° Ls) produced the similar result.
[Furthermore, as will be reported below, FALSARELLA (NFl) observed the intensity of Hellas to be 0.0 on 18 Mar (092° Ls) at ω=310° W. Refer also to NIKOLAI (ANk)'s work on 22 Mar (094° Ls) below.]
We may therefore put forward the threshold 090° Ls as the season the Hellas this apparition proved to be very active at least in the afternoon. Any CCD image without use of the B light was useless on this point.The problem remains about the morning Hellas. Hellas behaves differently to Montes in the northern hemisphere. Since Hellas is a deep basin and its activity must be caused by a frost of CO2 or a low-lying aerosol, the activity should remain unchanged diurnally if it is very active (on the contrary the cloud over Mons becomes more active on the afternoon side). This implies we should check the morning Hellas if we are to declare Hellas is in a very active state.
We could observe the morning Hellas from 10 Apr (102° Ls, ph Ang =19° ), but it proved not so prominent in brightness and white-colour. From 10 to 13 Apr, we observed at Fukui as follows: At ω=280° W, Hellas was well whitish bright (but not glossy), but at ω=270° W, it was white but not bright. At ω= 260° W, it was just whitish, and at ω=250° W, quite dim whitish (while Ausonia lighter but off-white). On 14 Apr, the surface at ω=240° W didn't show the presence of Hellas. [Exceptionally OHBA (Oh) saw Hellas to be just light on 15 Apr at ω=259° W, but didn't allude to its tint.]

Now choose phase angle is equal to 20° , and then Hellas, centred at ω =295° W, enjoys about 9:00LMT when seen from ω=270° W, since 90-20-(295- 270)=45° . On the other hand, SMITH & SMITH picked out the case of a very active Hellas in 1967 at 10:35LMT (cf CMO #134 p1253 Fig 3): The local time implies this time ω=295° W, and hence Hellas proved to be very bright. Since SMITH & SMITH regarded 10:35LMT as sufficiently in the morning, and they consider the case to be Very Active, we will be allowed to say that Hellas was fully Active or Very Active from around 090° Ls this apparition. [Note added: See also the observations by NFl below. A recent MarsWatch Web Site shows Don PARKER's B-light CCD on 31 Mar (098° Ls) at ω=267° W in which Hellas is very bright.]

We should say however even the brilliant evening Hellas was not simply and uniformly glittering but it shows a structure inside: As seen by Mn on 11 Apr at ω=309° W by use of 630× 20cm OG, the central part of the evening Hellas was made of the brightest, but the southern part, divided by a shadowy rift, is less bright, and also the northern part looked relatively faded.
We should furthermore say that we need to chase the morning Hellas further since the frosted deposit in the early morning might be dully misted or hazed. [In 1982 on 8 May at 123° Ls, T NAKAJIMA (Nj) and the present writer intensity estimated Hellas at ω=261° W to be 1 or 2 where the npc was 0 by the use of an old 15cm OG of the Fukui Observatory. At that time, phase angle=27° .]

2) Mare Acidalium, Morning : M Acidalium seems to be stable when the npc is small, i.e. near from late-spring to summer, and it looked quite the same as the one revealed by the HST in 1995. This time also M Acidalium near the CM proved to be usual. We are now able to watch the morning Acidalium completely since the defect illumination moved to the morning side after opposition, and this period we at Fukui observed from 9 Apr (102° Ls) to 13 Apr a small but definite light patch near on the terminator (maybe at Tempe) following the morning M Acidalium which became conspicuous from around ω= 335° W (when phase angle=18° ), and could be chased upto ω=015° W. Id also detected this light morning patch on 12 Apr at ω=334° W. The morning Chryse mist was similarly light, and up untilω=350° W, Niliacus L and the southern part of M Acidalium were covered thick by the mist.

3) Syrtis Major, Evening and Morning : On 1 Apr, Syrtis Mj was caught near the evening limb, and at ω=341° W, we observed that an evening haze lay over the middle of Syrtis Mj (which is on a big slope side) from the evening limb to Aeria. This phenomenon was also seen on 9 Apr at ω=317° W. A simple calculation shows that Syrtis Mj was at about 1:00pm local time. Hazed the central part of Syrtis Mj, its northern end looked relatively darker. Id, though he does seldom allude to the presence of any thin and faint haze, observed the northern part of Syrtis Mj to be darker at ω= 295° W on 12 Apr.
Though not yet compared numerically, Syrtis Mj looks fatter at the morning side than near the evening limb because the area is a big slope facing to the evening side. After opposition, the true morning Syrtis Mj is observable appearing as a much fatter area since the dawn terminator is inside the disk. Notable is the fact the region including Syrtis Mj is largely morning misted, and inside it Syrtis Mj shows a faint green-bluish tint. Aria following Syrtis Mj is also morning light if the latter is much inside. This aspect was observable on 10~15 Apr from our side.

4) Elysium Mons : Elysium was light as a whole together with Cebrenia, but furthermore Elysium Mons (ω=213° W) was visible as a bright small patch on 12 Apr at ω= 251° W (phase angle=20° ) and on 13 Apr at ω=252° W/262° W. It was not particularly whitish because the spot was affected by the off-white colour of Elysium. On 11 Apr (103° Ls) at ω=280° W, it was near the evening limb, and it shined as a bright spot at the limb at ω=288° W on 12 Apr, and at ω=291° W on 13 Apr. The local time was about 1:00pm whenω= 250° W, and about 3:30 when ω=290° W, and hence it will become much harder to watch the evening Elysium Mons (as well as other Montes).

5) The North Polar Region : The north polar cap (npc) looked to be in a stationary state. The western part of Olympia was clearly observed by Id on 12 Apr from ω=295° W to ω=334° W adjacent to the evening side of the npc. It is however difficult to determine the west end of Olympia: At Fukui we saw the white Olympia from ω=251° W on 12 Apr, but the west end looked ambiguous for our resolving power.
In addition to Olympia, we also saw a white detachment located rather at the morning side of the npc seen from ω =309° W (on 11 Apr) or from ω=317° W (on 12 Apr). This was checked as a light slit on 13 Apr at ω=252° W / 262° W. This had also been observed as a sinking detachment in a shape of tongue adjacent to the very evening side of the npc on 1 Apr at ω=010° W.
On the other hand, there was observed a rather large but faint white rough patch inside Cydonia on 1 Apr at ω=351° W, and this was also visible again on 10 Apr at ω=345° W. Id detected Chasma Boreale on 12 Apr from ω =295° W on.

Overseas Observations
From the Americas :

CAVE (TCv) observed on 1 Apr atω=255° W, about ten hours earlier than our times. Seeing is said to be steady good; several light spots being revealed, but the shape of Utopia looks unfamiliar to us.
FALSARELLA (NFl), as already cited in the text, observed that Hellas was already bright on 18 Mar (092° Ls) at ω=310° W with intensity 0.0. He checked it similarly on 20 Mar (093° Ls). However on 23 Mar (094° Ls) at ω=295° W he denoted Hellas to be 0.1 (while the npc 0.0). On 24 Mar atω=265° W, Hellas again 0.0 (at the same time Elysium 1.0). The morning Hellas on 26 Mar (096° Ls) at ω=240° W was 1.5, while 0.2 on 28 Mar (097° Ls) atω=270° W. On 30 Mar at ω=235° W, Syrtis Mj was seen well but no trace of Hellas. His observations in April all chase the evening Olympus Mons. On 4 Apr at ω=160° W, Olympus Mons showed intensity 0.8 while the more evening Tharsis 0.5. CCD images on 4 Apr at 0:05GMT and at 23:05GMT both show Olympus Mons but no npc, and thus the images look unbalanced.
SUDWISCHER (HSw)'s Video CCD was taken 14 Apr at ω=123° W. TROIANI (DTr)'s drawings were taken 1 Apr at ω=246° W, 2 Apr at ω= 227° W, 8 Apr at ω=147° W, 9 Apr atω=160° W, 14 Apr at ω=125° W, and 15 Apr at ω=106° W.
SCHMUDE (RSc)'s bright Hellas was at the evening side; on 23 Mar at ω= 325° W and on 27 Mar at ω=315° W (cf LtE in #188 p2056. He posted however the report to us on 8 Apr). Colour photos show a tiny planet with Syrtis Mj. On 27 Mar he took four pictures by changing filters successively, but the implication of the result is unclear to us.

From Europe :
Among the CCD images by DIJON (JDj), the one on 22/23 Mar at ω=289° W is the sharpest, showing such minor details as N Alcyonius and Boreosyrtis. Elysium is bright near the evening limb. Hellas is however dull near the CM because the R light prevails. On 1 Apr at ω=165° W and 2 Apr at ω=155° W, Olympus Mons, Tharsis ridges as well as Alba are seen evident. The shape of Propontis I is however not very sharp. Elysium looks light on the morning side preceding the Aetheria dark patch. We count the photos to be a one set when they are taken within 40 minutes.
GROSS (HGr) observed on 7 Apr at ω=090° W and on 8 Apr at ω=078° W. Both carefully show a light core on the evening limb preceding the sinking M Acidalium, which is also shown in the CCD images by GQr below.

8 Apr/ SGPG QUARRA (GQr) and Andorea LEO and others of the SGPG produced again excellent images on 8 Apr (101° Ls) at ω=101° W and ω=111° W (classified by the IR images. The file is composed of 8 images in all). Solis L in a shape of an egg-plant and Tithonius L et al are well produced. The Tharsis ridges including Ascraeus Mons are very bright through B(420nm) and G(530nm). Tempe and Alba are fainter but clearly shown. Olympia is seen adjacent to the npc in the morning side. The configuration of the images are similar to the one presented schematically at page 2050 in the previous issue of the CMO (#188). The colour images on the monitor really produce the "densely reddish" areas. The evening light patch at the limb (observed by GHr) is clearly visible in the CCD images at the slit between the bottom of M Acidalium and Hyperboreus L.
SIEGEL (ESg) took the drawings on 4 Apr atω=129° W, 6 Apr at ω= 101° W and 15 Apr at ω=021° W. The surface on 6 Apr (101° Ls) coincides by chance with that of an image on 8 Apr by GQr and others. Interestingly ESg detected on the surface the so-called Equatorial-Band Cloud (EBC) across it by use of Int, W80A and even by W47. As shown in the figure at #188 p2050, the hazed region is much detailed, and so her observation shows that the so- called EBC is of a gross structure of a series of haze patches (ESg is keen in the blue light). She identified the "densely reddish" dark area near the centre to be Ascraeus Lacus in accordance with some old map. On 15 Apr, ESg depicted M Acidalium divided to two: the lower the darker and the upper the fainter. The lower one must correspond to a west-side triangular darker region inside the M Acidalium (to be checked slightly later near the CM).
TEICHERT (GTc) observed on 1 Apr at ω=139° W, 6 Apr at ω=091° W, 7 Apr at ω=089° W, 8 Apr at ω=062° W, 9 Apr at ω=064° W, 10 Apr at ω=052° W and 13 Apr at ω=045° W. All observed in the evening. The centre of the images is not well detailed, and the npc is too small.
WARELL (JWr) made drawings on 4 Apr at ω=152° W, 7 Apr at ω=163° W, 12 Apr at ω=027° W, and 15 Apr at ω=022° W. On 12 Apr JWr experienced very good seeing at the Uppsala University Astronomical Observatory (by use of a 16cm OG), and saw all the possible markings: Deuteronilus preceded a complete M Acidalium. Nilokeras was inside the morning mist. Tempe bright in W25. A rift inside the npc was visible running from Hyperboreus L, possibly Chasma Boreale.
NIKOLAI (ANk) was late, but reported that on 22 Mar (094° Ls) at ω= 263° W, Hellas was bright thru B+W 041 (Orange). Another one was made on 29 Mar at ω=194° W.

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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