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th Report:
The CMO/OAA Observations made
during a fortnight period
from
16 February
2004 (351°Ls)
to
15 March 2004 (005°Ls)
An OAA Mars Section article to be published in CMO #289 (25
March 2004 issue)
Masatsugu MINAMI, Director of the OAA Mars Section
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his time we deal with the period from 16 February 2004 (λ=351°Ls) to 15
March 2004 (λ=365°Ls).
On 5 March (ecliptic longitude=345° when in the oriental area the day is thought
that insects come out from the ground. In 2004 the planet Jupiter was at
opposition), the planet Mars welcomed the spring equinox λ=360°Ls: End of
one cycle. In the 2005 apparition it will occur on 20 Jan 2006, and in the case
of 2007/2008 apparition, it does on 9 Dec 2007: Since in 2007 the planet will
be closest to the Earth on 19 Dec 2007, and hence the 2007 apparition is for
the northern seasons.
This period above, the apparent diameter decreased from δ=6.1" to 5.3". The central latitude was from φ=26°S
to 13°S. So gradually the northern hemisphere became easy to see. The phase
angle was from ι=38° to 34°.
This time we received
precious observations from the following members:
AKUTSU, Tomio (Ak) Karasuyama,
2 Sets of (IR)RGB Images (20, 22 February 2004)
f/33×32cm spec with a Bitran BJ-41L
IWASAKI, Tohru
(Iw)
9 Drawings (16, 17, 29 February;
13, 14 March 2004)
400×21cm speculum
KUMAMORI, Teruaki (Km) Sakai, Osaka, Japan
18 CCD Images (18, 20, 25,
27, 28 February; 5, 6, 9 March 2004)
f/40×60cm Cass#
with a ToUcam
#
MELILLO, Frank J (FMl)
3 Red CCD Images (16, 28
February; 12 March 2004)
20cm SCT with a Starlight Xpress MX5
MINAMI, Masatsugu (Mn) Fukui,
30 Drawings (18, 19, 20 February; 10 13,
15 March 2004)
400, 480, 600×20cm F/12 ED Goto refractor*
*
MORITA, Yukio (Mo) Hatsuka-ichi,
19 Sets of (IR)RGB Images (20, 21, 29 February; 4, 9, 13, ~15 March
2004)
25cm spec equipped with an ST-5C
MURAKAMI, Masami (Mk)
5 Drawings (16, 20+, 27, 28 February 2004)
320×20cm speculum, 320×15cm
refractor+
+ Kudan High-School
Observatory,
NAKAJIMA, Takashi (Nj) Fukui,
8 Drawings (13 February
2004)
480, 600×20cm F/12
ED Goto refractor*
*
PARKER, Donald C (DPk)
1 Set of RRGB Images
(23 February 2004)
f/59×41cm F/6 spec equipped with an ST-9XE
SIEGEL, Elisabeth (ESg) Malling, Danmark
6 Drawings (18, 19, 23, 29
February; 3, 7 March 2004)
270×20cm F/10 SCT
TEICHERT, Gérard
(GTc)
2 Drawings (16, 20 February
2004) 330×28cm SCT
WARELL, Johan (JWr)
4 Sets of CCD Images (18, 23 February; 1, 9 March
2004)
f/24×25cm
SCT with a ToUcam
The
NPH or NPC: That is a question
which occurs if the season arrives at λ=350°Ls: that is, we wonder
if the white matter located at the northern limb is the north polar hood (nph)
or the north polar cap (npc). It is generally
believed the npc is brighter than the nph, but it is
not necessarily the case. The npc should not be
usually clear if we do not quite pass the vernal equinox. This time there are a
lot of observations which show the white and bright northern limb matter. For
example, on 18 Feb (λ=352°Ls) Teru KUMAMORI (Km)
showed the nph clearly at ω=238°W~251°W. On 23 Feb (λ=354°Ls)
Don PARKER (DPk) claimed that a bit of the npc
was seen (in a lull ?) on the R image at ω=076°W, though the following nph is
brighter. The B image largely shows a thick nph. Yuki MORITA (Mo)
also produced a set of images at the same angle at ω=077°W on 9 Mar (λ=002°Ls), and its
IR image shoed similar bright white matter near 
the northern limb. His B also shows it
thickly. According to Masami MURAKAMI (private
communication), however, this cannot be considered to be the npc, but still the nph since Mo’s IR image from the
set of images on 13 Mar (λ=004°Ls) shows it from a different angle
(by50°W) at ω=025°W, and apparently it is not
perpendicular to the NS line (fortunately Mo always associate w← on the
files and on the day exactly w← declines by 37°). On 9 Mar, φ read 14°S with
δ=5.4".
So we may first employ W BAUM’s
plateau (see CMO #109 – 25 Sept 1991 – p0944), then the snow line should be 64°S at λ=010°Ls. However BAUM’s guessed plot shows 55°S on λ=000°Ls (spring equinox). On the
other hand, JAMES and others obtained 60°S at the equinox from the Viking data in
1977/1978 (JGR 84 (1979) 8332,
Icarus 52 (1982) 565).
Otherwise they also pinned down 58°S from the Viking results during the
elongated period in 1979/1980 (Icarus
52 (1982) 565)(they claimed in this case there was not occurred the Baum
plateau because of a presence of the dust disturbance – see reviews in CMO #130
– 25 Feb 1993 – p1199). So here we employ the largest case of the snow line at
55°S on λ=360°Ls, then the half angle of the npc
must be ψ=35°, and since φ=14°S, we can calculate the depth d of the npc
by the formula d/r=1 – cos(ψ – φ) where r is a radius. This
formula was first given by A DOLLFUS in Icarus
18 (1973) 142, and its derivation was given in CMO #003 p0017, and also
cited in CMO #255 – 10 Jan 2002 and in CMO-Web: See the Appendix in
http://www.kwasan.kyoto-u.ac.jp/~cmo/cmomn0/01Note01/index.htm
Since ψ– φ=21° , the above formula gives d=r×0.066. If we employ a disc of 5 cm diameter,
the depth at the CM is no larger than 1.7 mm. When φ is too south, the ambiguity
increases: If we employ the JAMES and others case (58°S instead 55°S) d is down to 1.0 mm. Even if we are
given 2mm/50mm, d should be said too
small. And so we should say the npc must have still
been buried inside the nph this period. It looks the seeing condition on 9 Mar
was better than on 13 Mar, but even then the nph prevailed on Mo’s
images on 9 Mar. We would like here to express our respect to MORITA’s work which is always accompanied by the record of
w← on the file which otherwise bothers him. The work on 13 Mar proved
thus very precious with the attachment of w←. The B image is also
helpful.
Before Mo, the visual observer Elisabeth
SIEGEL (ESg) did not record the northern limb to be bright by the use
of W25 on 3 Mar (λ=359°Ls) at ω=239°W, but on 7 Mar (λ=001°Ls)
at ω=203°W the W25 observation gave her a bright northern limb, but not in
the form of the npc.
The Km-images on 18 Feb (λ=352°Ls) at ω=238°W~251°W
does not naturally show any dark band around the nph, while Johan WARELL (JWr)’s
images on the day at ω=155°W looks to show a
perimeter. On the other hand, Km’s image on 28 Feb (λ=357°Ls) at ω=151°W does
never show it. The true description of any dark band is difficult at this time,
even Utopia, though visible in G of Mo’s images on 20 Feb (λ=353°Ls) at ω=258°W, is vague
on Mo’s
images on 21 Feb (λ=353°Ls) at ω=218°W~240°W. On
the other hand JWr’s images on 1 Mar (λ=358°Ls) at ω=045°W clearly
show the dark M Acidalium to the south of the nph.
The present writer was unable to observe from
21 Feb to 9 Mar because of the dismal weather, but on 10 Mar (λ=002°Ls),
the sky recovered and he could look for the npc: the
limb looked to suggest it, but not bright and uncertain. On 13 Mar
(λ=004°Ls), the situation was the same: Takashi NAKAJIMA (Nj) also tried to search, but he was also not sure: Just
later at ω=028°W, 038°W Nj suspected the presence of the npc. Tohru IWASAKI (Iw) on the same 13 Mar recorded “a whitish fine light
piece” along the northern limb, but noted it was not bright. The germinant npc was not necessarily bright when seen near the limb, and
so it is possible for Iw to have seen the 2mm npc on 50mm disc. Iw gave similar
results on 14 Mar (λ=004°Ls) at ω=021°W. Mk tried to check the npc but in vain
during this period.
The SPH: Km’s images on 20 Feb (λ=353°Ls, δ=6.0") at
ω=224°W~238°W are excellent: M Cimmerium is evident and
Hellas’ Atmosphere: This time the ccd
observations of
Markings: DPk’s excellent images on 23 Feb (λ=354°Ls) at ω=076°W show
Argyre without any cloud, and clearly resolved such markings as Solis L,
Tithonius L, Nilokeras and so on. On 5 Mar (λ=360°Ls) at ω=075°W~091°W and on 6 Mar (λ=000°Ls)
at ω=077°W, Km shot the area but
Solis L was not separated. However on 9 Mar (λ=002°Ls), Km was endowed with a
good seeing and at ω=040°W~056°W resolved Sinus Meridiani, Aurorae S and M
Acidalium, but no longer Solis L. The nph was very white.
Others: ESg’s observation on 3 Mar (λ=359°Ls) at ω=239°W showed a bright patch near the
evening limb around Phaethontis through Wr47. Mn noted on 10 Mar
(λ=002°Ls) at ω=035°W that the central deserts are especially
“reddish.” Still evening, and inside the dome 14°C.
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he
next issue shall treat the observations made during the one-month period from
16 March 2004 (λ=005°Ls) to 15 April 2004 (λ=020°Ls, δ=4.6").
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