Forthcoming 2005 Mars
(14)

Water Vapours Seen on the SH from λ=320Ls to 360Ls and Hellas at around λ=345Ls

 

Masatsugu MINAMI


Japanese here


T

he Viking mission in 1977 brought about rather unexpected results in addition to a lot of usual anticipated ones: As an example it revealed a rich distribution of water vapour on the southern hemisphere at the season of southern summer solstice λ=270Ls, and secondly, as this may also be related with the former, the water vapour was seen to go down from the southern high-latitude area to lower equatorial region from λ=330Ls to λ=360Ls. (These were treated in CMO #108 -25 August 1991-, based on B JAKOSKY et al, Icarus 73 (1988) 80, J POLLACK et al, Icarus 50 (1982) 259.)

 

What we recall here may be related with the second result, and may be observable similarly this apparition. That is the observational fact that in 1990, around from λ=340Ls, there were observed one or two (sometimes three) patches of the water condensates on the following terminator from the higher to lower latitude (as reported as a Note in CMO #108 p933). In short, from the time S Sabaeus was near the meridian to the time when Hellas was near the morning terminator, several conspicuous condensate patches were witnessed on at-dawn Noachis when it passed the morning terminator, especially from 3 December 1990 (λ=344Ls) to 10 December 1990 (λ=347Ls) (Just from Japan): This is first based on Mns 65 observations from 3 Dec to 10 Dec 1990 and also on Takashi Nakajima (Nj)s 29 observations from 6 Dec to 10 Dec 1990, while at the same time a lot of observations were made in Japan. On 1 Dec (λ=342Ls) 1990, Tohru IWASAKI (Iw) visually watched at ω=322W, and Tomio AKUTSU (Ak) took a B image (B390) at ω=336W, both show two condensate terminator patches, one at a higher region and the other at Margaritifer S. On 3 December 1990, Isao MIYAZAKI (My) produced three sets of TP images (B390); one at ω=320W showed the one at the higher region was divided into two terminator patches, and at ω=342W there was added the third one over Margaritifer S. The observers of the repeated terminator patches were counted, in addition to the above five, as follows: Naoya MATSUMOTO (Mt, RD100), Hiroshi ISHADOH (Id), Akinori NISHITA (Ns, RD100), Masami MURAKAMI (Mk), Morimasa NAKAJIMA (Nk) and others. Mt chased on 9 Dec 1990 by RD100 the planet at ω=246W, 256W, 262W, 272W, 281W, 306W, and 316W.

From Japan, the observation of the conspicuous patches ceased around 10 Dec (λ=347Ls), while the last pattern was as such: From around ω=250W, there appeared a cloud patch to the south of Hellas, and it became richer and remained near on the terminator. At around ω=310W, it became split into two, but this looked to happen because of the rich darkness of the area of Depressiones Hellesponticae.

 

Abroad, Don PARKER (DPk) was a unique observer at that time who secured the B images. One of his colour images taken on 24 November 1990 (λ=334Ls) shows this kind of patch (he produced B through the colour films). We can say however if we compare DPk's image on 23 Nov 1990 at ω=297W with My's image (Int) made on 7 Dec 1990 at ω=295W, the latter shows the limb cloud paths more clearly and strongly. One month later, DPk showed a patch to the south of Hellas on 24 December 1990 (λ=254Ls) by the use of TP equipped with the B390 filter. His image on 31 Dec (λ=358Ls) at ω=280W shows that the core was much downward compared with the case at the beginning of December, and this was in good accord with case of the Viking result. That is, this kind of phenomenon was a seasonal one.

 

Hellas even when more inside looked also irregular, and at the western corner a strange stream swath of light matter prevailed along Yaonis Fr (the northern part of Hellas was a thick haunt as usual). This irregular phenomenon of Hellas was noted in CMO #113 (25 Jan 1992 issue) p989 (as Note (3), with Figure at p989 shown here at the rhs). This was quite apparent on 23 Oct 1990 (λ=321Ls) at ω=303W, 313W: The bright part was not whitish but slightly pinkish. This aspect was also detected by Iw, Ak and Mk. Already DPks TP photos made on 13 Oct 1990 (λ=315Ls) at ω=311W, 317W show this phenomenon, and so might have begun to occur before the limb-patch phenomena. He also showed it on 19 Nov, 20 Nov, and 23 Nov 1990. In Japan this was frequently observed in December: On 1 Dec 1990 (λ=342Ls), Iw and Id as well as Mn observed. Iw noted Hellas was not brighter as it approached the evening limb side. In photos, My made a series on 3, 5, 6, 7, 8 Dec 1990, and Ak also took on 5, 6, 7, 8 Dec 1990. They all show that the bar-like haunt does not show up in B, and so different from the limb clouds. On the other hand, in R it was evident even on the TP images by Mk made by the use of 10cm Refr on 8 Dec 1990 at ω=291W, 301W. We should say the haunt is however weak on Mts R100 images.

 

Fifteen years ago, any concentrated observations did not reach us except from the Japanese observers, while this apparition we can expect to accumulate globally more complete data of the same phenomenon from around the world, if not obstructed by the dust covering.


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