1996/97 Mars Sketch (1)
from CMO #197 (25 November 1997)

-- White-Cloud Burst over Elysium to the Morning Side
at 107Ls -- HIGA's Observation --

Japanese here


rom Japan, a thick morning white cloud was observed from the southern part of Elysium westwards to the morning terminator from 19 April (106Ls) to 22 April (108Ls). This phenomenon was visually caught by several observers but most nicely caught by the Video images by Yasunobu HIGA (Hg) at Okinawa as reported in #190 p2084 by use of a 25cm spec. Especially the cloud on 20 April was conspicuous and burst-like, consisting of two thick cloud patches, one over Elysium and the other over Aethiopis to Libya. We don't claim that the cloud was particularly conspicuous only at the period, but to extend the discussion we need to obtain overseas observations of the area before and after the period.

Doubled cloud patches on 20 April are most vividly seen on the images by Hg (processed from the Video images taken by Sony DV Camera VX 1000) taken around 11:55 GMT at ω=210W (12:03GMT at ω=212W, 12:12 GMT at ω=214W etc). We also have a moving image around 11:20GMT at ω=202W in which the following part of cloud is not yet clear, but Elysium is well misted and an overflow is seen to the south of the Aetheria dark patch. (According to the information recently received, Hg observed from 11:19 to 12:24GMT on the day.)

The print images at 11:55 GMT ω=210W are made of red and blue images in addition to the integrated colour image; and the blue one most clearly shows the doubled cloud, and hence it must have been a series of white clouds. The season on 20 Apr was 107Ls, the apparent diameter was 12.5", and the phase angle was 25 degs.

Hg also took pictures on 19 Apr and 21 Apr. The image on 19 Apr at ω =225W shows the afternoon Elysium to be light but any protrusion of the cloud westwards is not so evident while the morning terminator is misted (maybe over Syrtis Mj). Recently Hg informed us that he continuously shot from 12:46 to 13:21GMT and sent us a processed print at 12:48GMT ω=232W where a long tail of cloud from Elysium to the morning limb is visible in blue (but less in green).

The images by Hg on 21 Apr were first sent us by moving ones as reported in #190 p2084 which were taken at 1) 11:40GMT ω=193W, 2) ω=202W, 3) ω=212W, 4) ω=222W, 5) ω=232W and 6) 14:40GMT ω=241W. In 1), Elysium is still near the morning terminator. Image 2) is poor. 3) shows the same angle as the one on 20 Apr when the cloud was conspicuous, but here it is not so vivid, looking dispersed. Elysium is well whitish light. (Seeing was however 5/10 on 21 Apr while 7~8/10 on 19 and 20 Apr). Image 4) shows two patches of the clouds though the following part is weaker. In 5) no more than Elysiums light (Cebrenia visible). The same in 6). Afterwards we received from Hg processed prints of some of the 21 Apr images: the cloud patches really prove to be weaker in all.

As reported in CMO #190, Tomio AKUTSU (Ak) took CCD images on 19 Apr at a) ω=213W and on 22 Apr at b) ω=183W, at c) ω=202W, at d) ω=218W, at e) ω=236W ( in #190 p2082 the Red images were counted, but here images in B light are picked out). Image a) shows vaguely the two patches, and in c) and d) we can also see weakly the cloud, but these images are not comparable with those by Hg.

Visually Hiroshi ISHADOH (Id) observed on 19, 20 and 21 Apr: He detected the morning mist large on 19 Apr at ω=223W. Id's observations on 20 Apr are somewhat late (ie at ω=240W and 250W). On 21 Apr at ω= 212W and at ω=222W, the morning mist remains to be large but not connected with Elysium (Id's light Elysium is concentrated around Elysium Mons).

The present writer (Mn)'s observations on 19 Apr qualitatively show that at ω=220W a morning mist preceding Syrtis Mj was present independent of Elysium (so very the same as Id's observation), but that at ω=240W, the following cloud was not obvious. On 20 Apr NAKAJIMA (Nj) and Mn observed at 1) ω=189W(Mn)/194W(Nj) that the area from the morning terminator to Elysium was already covered by a large morning mist, at 2) ω=199W/204W, the morning mist was still large, at 3) ω= 209W/214W, the morning cloud hung over Elysium, at 4) ω=219W, the cloud looked made of two patches; divided by the presence of the Aetheria dark patch, and at 5) ω=228W, no longer the following patch was visible, though the morning mist preceding Syrtis Mj was present. Observed up to ω=248W. The observations complement those by Hg on 20 Apr, though the comparison is not simple.

DPk's Image
The MarsWatch Web-site shows the CCD images by Don PARKER (DPk) on 7 Apr (101Ls) at ω=208W where Elysium is light and the area near the morning terminator is misted. On the other hand at the end of May from Japan, a similar aspect was observed. For example, the present writer (Mn)'s observations on 28 May (125Ls) depict a similar aspect at ω=190W, ω=200W, ω=210W, ω=219W, ω=229W, ω=239W etc. The records in 1995 also show that a similar phenomenon was observed on 31 Apr 1995 (078Ls) at ω=215W and on 4 Apr 1995 (080Ls) at ω= 217W (when the apparent diameter=10.1").

Accordingly, we may consider that the phenomenon must have lasted during a longer period, but at present no other neighbouring observations are obtained. (MarsWatch web-site pages are insufficient in this sense.) As far as we check our observations as stated above, we are thus inclined to favour the conclusion that the cloud activity over the morning area over Elysium to Libya was very conspicuous around 20 Apr (107Ls).


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