Forthcoming 2005 Mars
(9)
Watch the
Masatsugu MINAMI
|
T |
his time we feature the period when the north
polar region is attentively observed, though not easy to observe.
It is quite natural to refer to the
situation of Mars in 1990 as we did in order to seek a guide in observing the
coming 2005 Mars since a cycle of 15 years gives an easy recurrence of the
similar Mars (season, diameter, and so on).
As to the recurrence periods, the
present writer once gave an idea in The
Heavens (OAA Journal, in Japanese) vol 65 (1984) p185, and repeated it in
English in CMO #106 (15 June 1991) p910
(see Web Page).
Essential point is this: Let m and n be integers. Then if
we can choose m and n in such a way that the rational number n/m
is akin to an irrational number 7.390..., the combination 2n+m gives
a good recurrence period. Proof of this
proposition was given in CMO #106 p910 and here reproduced in its Web page. One of
best approximations is given by the choice n=133 and m=18, so
that n/m=7.388 which is quite near 7.390 and 2n+m gives 2×133+18=285. The recurrence period of 285
years looks therefore the best if we seek years in hundreds. The period of 15 =
2×7 + 1 years is given by the approximation 7/1=7.000, and the period of 17
= 2×8 + 1 years by 8/1=8.000: Thus any possible recurrence years are fallen
between 7 and 8, and the more plausible ones are the nearer ones to 7.390. The
well-known 79 year period is given by 37/5=7.400 and so we should say this is
one of better approximations (note however 7.400 - 7.390 = 0.01, while 7.390 -
7.388 = 0.002).
This time, though slightly inferior to the
above examples, we pick out the case 66/9 = 7.333… . (7.390-7.333 = 0.057). The recurrence period
then gives 141 which implies we choose 1864 = 2005 - 141 as a plausible year as
a guide for the 2005 case. In 1864, the planet was closet to the Earth on 23
November, and the maximal angular diameter was 17.5 arcsecs.
Since in 2005, the very day occurs on 30 October, it looks slightly far. In
fact another opposite choice of 67/9=7.444 (7.444-7.390 =0.054) gives a
recurrence in 143 years, and hence the next 2007 apparition is also similar to
the 1864 one (in 2007, Mars is closest on 18 December). That is, the 1864
apparition is ambivalently approximate both to the 2005 and 2007 apparitions.
In other words, what we are to describe about 1864 is also applicable in the
next apparition. On the other hand, we can prove the 1864 apparition was more
akin to the 1990 one, since 1990-1864 =126, whose recurrence is given by the
rational number 59/8=7.375 and 7.39-7.375 is only 0.015. It is needless to say
the 1864 apparition was more akin to the 1943 case.
Remark that 66/9 which gives 141
recurrence year is equal to 22/3, and so it is no more
than a repeating of 2×22+3 = 47 yrs recurrence. 47 = 15+17+15, and so the case of 1864 is not so
different from the rough approximation which we meet if we use the 1958
apparition (in 1958, the planet was closest on 8 November with the maximal
δ＝ 19.2"). Incidentally, the Lowell and Barnard year
1984 is given from 2005 by the 111 year recurrence of 52/7=7.428 (7.428 - 7.390
= 0.038), and not so bad.
The season when the planet Mars was closest
to the Earth was respectively λ=299°Ls in 1894, λ=315°Ls in 2005, λ=320°Ls in 1958, λ=336°Ls in 1990 and λ=341°Ls in 1864.
These apparitions more showed the southern hemisphere and therefore were not so
pertinent to the watching of the high latitude region of the northern
hemisphere, while they provide large disks of Mars in the season after λ=300°Ls.
Recently it has been
recognised to be important to pay attention to the north polar region in the
periods (A) from λ=210°Ls to λ=230°Ls, and also (B) from λ=310°Ls to λ=350°Ls because there seem to arise some dust disturbances
at the northern high latitude areas in these periods and some of them develop
into the so-called cross-equatorial dust storms. We learned from Christophe
PELLIER, private communication, that the dust storm detected by Don
PARKER in December 2003 was one of the cross-equatorial dusts, and PELLIER also
speculates other two storms observed in 2003 (including the interesting
June/July one) were originated from the northern hemisphere. Note that the
December storm was detected at λ=315°Ls, and so belonged to the period (B). In
2003, the angular diameter at the season was only 9.9 arcsecs,
while in 2005 the season visits when the diameter is maximal.
We should call attention of the readers to
the MGS Weekly News in 2002 (from January to September) in http://www.msss.com/mars_images/moc/weather_reports/
where we can find several images of dust
occurrences at the northern high latitude areas; for example at Xanthe at
λ=315°Ls, at Chryse at λ=328°Ls, at Utopia at λ=342°Ls, at Chryse at λ=350°Ls and so on.
In 2005, the season λ=310°Ls of (B) comes on 21 October with a large
diameter of δ=19.9", and the final season λ=350°Ls will visit at the beginning of the next
year when δ keeps still 12" ; and hence the 2005 apparition provides a
good opportunity to do the watching during the period (B). We should especially
choose the periods when M Acidalium or Utopia is visible.
|
W |
e are now in a position to state the reason why we pick out the 1864
apparition: It is because the north polar hood was attentively observed in 1864
maybe for the first time. According to the list made by C FLAMMARION, in 1864
such observers as GREEN, BANKS, WILLIAMS, KAISER, DAWES, SECCHI and others were
active (also in 1864 HUGGINS and others made spectroscopic observations to
detect water vapour on Mars). ANTONIADI reports that F KAISER made an
observation in which M Acidalium was completely covered by the white cloud
(north polar hood=nph). Among them William R DAWES (1799-1868) produced some
impressive observations of the north polar region. DAWES's observation in 1864 had really a good reputation,
and no other than KAISER's could rank with his. DAWES
used in 1864 a 20 cm Cooke refractor with a magnification 258×: It seems to be quite low from our
view-point and when the seeing was poor, he even used 155×. DAWES however was said to have the keen
eyes though he used a thick eyeglasses (W SHEEHAN, The Planet Mars, 1966,
p53f).
The BAA inherited all of 16 drawings of DAWES
made in 1864, and in 1988 Richard J McKIM and Robert
A MARRIOTT published them in a beautiful printing set in JBAA 95
(1988) No 6 p294: Until then a set of 8 drawings were known in a lithograph
form, but in the article all (including other 8 unpublished drawings) were
reproduced from DAWES's original drawings in a
photograph form (for the first time).
The DAWES drawings are important in several
respects, but among them they are important since they depict clearly the
variation or activity of the nph. On 20 November and 26 November (λ=343°Ls), the wavy nph was caught to the north of
Syrtis Mj, and on 13 November and 15 November (λ=337°Ls, δ＝17.3", φ=4°S) the nph was interestingly depicted at the
angles where M Acidalium stayed. By courtesy of Dr R McKIM,
we can here show the photographic copy of the original drawing on 15 November
at 00:00 GMT (new GMT system): Its lithograph was already cited in CMO #106:
Compare with the drawing in 
the Web Page
DAWES himself described that a “short and rather thick dark line" which was observed on 14 November
(12h) had not been visible on 12 November (old GMT system) and as also
suggested by R McKIM and R A MARRIONETT this drawing
shows the phenomenon which must have shown a popping out of the southern part
of M Acidalium from a window of the thick nph. This kind of nph activity is
common in this season, and also since belongs to the period (B)
must be related with the dust onsets near the npr if any.
Note also that the DAWES drawing shows, in
addition to the clear detection of Aryn Fastigium (Dawes' forked bay) a strange canal called Hydaspes and Sinus Hydaspis which
ran from Margaritifer S to Niliacus L: This was a temporary dark marking which
was apparent from 1851 to 1871: It was first detected by Angelo SECCHI, and
observed in 1862 by J N LOCKYER, and in 1864 by KAISER and DAWES. Sinus Hydaspis (named by ANTONIADI) was a kind of the river mouth
of Hydaspes (named by SCHIAPARELLI).
Hitherto the relation of several secular
changes of the dark markings on the northern hemisphere and the activity of
dusts has not fully been discussed (nor observed), but it was quite possible
for the strange secular change (appearance and fading) to have been caused by
the activity of the northern dusts which were switched by the atmospheric
activities at the npr. Unfortunately such detections
were not made those times because the observations were scarce and the tilt of
the north pole was quite away from the Earth.
As frequently remarked, the area
from
The northern tail of Syrtis Mj, or Nilosyrtis, is also not the same at present as the one
SECCHI called Syrtis Mj Scorpion (or blue Scorpion in the morning).
DAWES' drawing on 26 November describes Nilosyrtis in
connection with the nph expansion.
We already discussed the
activity of the nph in the 1990 apparition in (6): Finally we cite here an
observation made by the present writer on 22 October 1990 on which
day the nph kept a bit away from a part of M Acidalium, as shown in the diagram
shown in
http://www.kwasan.kyoto-u.ac.jp/~cmo/cmomn2/1990oct_nph.gif
and the very drawing shows
the moment when the part was seen dark as a segment as was quite the same case
as in DAWES'. The geometrical situation was similar since δ=16.1" and 
φ=4°S on the day, while the season was λ=321°Ls and earlier than DAWES's
case, though still inside the period (B). So such an activity lasts long. As
reported in (6), just after the interesting activity of the nph, a second dust
storm was observed from 2 November (λ=326°Ls): This is also inside
the period of (B), but unfortunately the accumulation of observational data was
few before the detection (because of lack of data in the Asia to Middle-East),
and no one can say whether it was a cross-equatorial dust storm or not, but
very possible. Fortunately no explicit secular change occurred.
In 2005, the situation will be
slightly poorer since the tilt will not decline more than φ=15°S during the period (B) so that it may be
rather difficult to observe the northern limb, but since the diameter still remain
large as pointed, there may be a little possibility to be able to witness a new
secular change of the dark markings in the northern hemisphere due to a rise of
the northern dust associate with the activity of the nph, if we thickly
observe during the period.