Mars Sketch (1)
from CMO #197 (25 November 1997)
-- White-Cloud Burst over Elysium to
the Morning Side
at 107°Ls -- HIGA's Observation --
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=210°W (12:03GMT at ω=212°W, 12:12 GMT at ω=214°W etc). We also have a moving image around 11:20GMT at ω=202°W 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=210°W 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 107°Ls, 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 =225°W 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=232°W 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=193°W, 2) ω=202°W, 3) ω=212°W, 4)
ω=222°W, 5) ω=232°W and 6) 14:40GMT ω=241°W. 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=213°W and on 22 Apr at b) ω=183°W, at c) ω=202°W, at d) ω=218°W, at e) ω=236°W ( 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=223°W. Id's observations on 20 Apr are somewhat late (ie at ω=240°W and 250°W). On 21 Apr at ω= 212°W and at ω=222°W, 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=220°W a morning mist preceding Syrtis Mj was present independent of Elysium (so very the same as Id's observation), but that at ω=240°W, the following cloud was not obvious. On 20 Apr NAKAJIMA (Nj) and Mn observed at 1) ω=189°W(Mn)/194°W(Nj) that the area from the morning terminator to Elysium was already covered by a large morning mist, at 2) ω=199°W/204°W, the morning mist was still large, at 3) ω= 209°W/214°W, the morning cloud hung over Elysium, at 4) ω=219°W, the cloud looked made of two patches; divided by the presence of the Aetheria dark patch, and at 5) ω=228°W, no longer the following patch was visible, though the morning mist preceding Syrtis Mj was present. Observed up to ω=248°W. The observations complement those by Hg on 20 Apr, though the comparison is not simple.
The MarsWatch Web-site shows the CCD images by Don PARKER (DPk) on 7 Apr (101°Ls) at ω=208°W where Elysium is light and the area near the morning terminator is misted. On the other hand at the end of May from
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 (107°Ls).