2001
Mars CMO Note
- 18 -
from CMO #271
Airborne Dust on 4 July 2001
THE following is to take
notice of two characteristics of the dusty atmosphere seen on 4 July 2001. One is an
observational fact detected around M Cimmerium, and the other is concerned with
a serious expansion of the airborne dust to the rear side by 4 July.
As repeatedly remarked, MORITA (Mo) produced a
series of images at LCM=212°W
from 1 July to 4 July, which shows how the airborne dust expanded to the
northern hemisphere causing serious changes of markings.
One feature proven on the images is an existence of an extraordinarily
dark patch near the western part of M Cimmerium and its development from 1
July. The patch stayed at the same place during (at least) four days while
became darker day by day. Unfortunately we have no data after 4 July, but it
was darkest finally. On 4 July, Mo observed until around
LCM=220°W. At the Fukui City Observatory, NISHITA (Ns) and the
present writer (Mn) stayed longer on the day, and Ns produced a set of R, G, B
images at LCM=225°W that shows the patch more inside. An RGB image is cited
here, but the one in the 2001 Dusty Mars CMO-Web is an
LRGB image.
We are of the opinion that the strange dark
patch appeared just darker since the yellow cloud around the hole became
thicker and brighter day by day. No appropriate MGS-Swath is found on 4 July,
while the one at 233°W on 5 July (here cited) shows several minor craters
inside the hole, and hence the cloud must have really been thin at the patch.
We have no idea at present why the area was rather free from a furious dust
activity, but it was an interesting fact that it stayed nearly at the same
place; and thus dust devils as well as dust holes don't easily propagate as
conforms to our previous assertions.
This dark hole might have indicated to some visual observers that the
surface must have been free from the giant yellow cloud since "M
Cimmerium" looked visible.
Next set of swaths are made of MGS-Swath at
220°W on 4 July and similar Swath previously taken to be compared. To
compare with a usual map, crater a, and several others are spotted. The a must be the Kepler crater at
(219°W, 47°S). The line at 220°W is proven to have been covered by
serious dust to the deep North. Compare with Ns' image.
The last two images are also made of MGS-Swaths of 322°W and
351°W compared with the same angles in May. Comparison is rather easy,
since the dark markings are still seen to the extent that they might be well
dark if enhanced in the usual ccd images made from the
terrestrial basis. Here however it is quite apparent
the airborne dust had already reached the area of S
Meridiani by 4 July and made its details fainter. The other shows
that a dust disturbance was already onset at the area of the eastern Deucalionis
R (to the west of M Serpentis). We should say that the yellow cloud that
started on 24 June was already established to be quite global by 4 July even if
there were several holes of dust. It was no use to expect and wait for any soon
clearance.
We finally note the
MGS Swaths are from:
http://www.msss.com/moc_gallery/e01_e06/globalmaps.html
(M MINAMI)
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