1996/97
Mars Sketch (1)
from CMO #197 (25 November 1997)
-- White-Cloud Burst over Elysium to
the Morning Side
at 107°Ls -- HIGA's
Observation --
|
F |
rom 
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=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).
(Mn)