THE planet Mars was at conjunction with the Sun on 12 August 2002, as was really checked by the SoHO/LASCO (Large Angle and Spectrometric Coronagraph Experiment), and now shines in the morning sky. We will find Mars at the morning Libra at the end of 2002.
In 2003, the planet will be closest to the Earth at Aquarius on 27 August at 10h GMT up to a distance of 55.76 million km. The maximal angular disk diameter on the day will rise up to 25.11 seconds of arc, the greatest in history. The planet will be at opposition on 28 August at 18h GMT along the ecliptic and on 30 August at 21h GMT along the RA. This large difference by two days must be caused because it moves backward at opposition when the orbit makes a loop.
1640 25.06" on 20 Aug 1687 25.00" on 9 Aug 1719 25.03" on 25 Aug 1766 25.08" on 13 Aug 1845 25.09" on 18 Aug 1924 25.10" on 22 Aug 2003 25.11" on 27 Aug 2050 25.02" on 15 Aug 2082 25.06" on 30 Aug
The greatest opposition in the preceding century occurred in 1924, 79 years before counted from 2003, while the least distance between Mars and the Earth was still more remote by 20 thousand km than in 2003, and according to Jeff BEISH the maximal apparent diameter in the 2003 case will become the greatest ever since the times of the Cro-magnon beings (cf CMO #258 & #259). The apparitions where the maximal apparent diameter was over 25.0" just occurred once in the 20th Century as well as in the 19th Century. In the 21st Century, there will be other two occasions in 2050 and 2082 when the apparent diameter reaches 25.02" and 25.06" respectively.
One of advantages endowed with is that if the maximal diameter is thus larger, we can observe the planet for a longer period in a better condition. In the last apparition in 2001 (Mars most approached on 21 June 2001 at 23 h GMT up to the apparent diameter=20.79"), we had just about one month when the apparent diameter was over 20", while in 2003 the apparent diameter will be larger than 20" for about two and a half months from 20 July to 4 October. In the subsequent 2005 apparition, the apparent diameter will be no larger than 20.17" (on 30 October) and so the period concerned will be quite short.
In 2003, the apparent diameter will be expected larger than 10" for six months from the beginning of May through the beginning of December.
Even if the diameter remains larger, we cannot observe every aspects of the planet: The central latitude will go up to deep on to the southern hemisphere from around April, and at June it goes up to around the central latitude=20°S. And so it will be hard to observe phenomena in the deep northern hemisphere. On the other hand, it implies we will be able to watch after a long while the details of the regions in the higher southern latitudes. We suspect it will be the first time for the HST to look down the higher southern latitudes.
Nowadays observations are not aimed to detect the minute details such as the canals, but are aimed to observe the seasonal changes on the Martian surface. The season changes in 2003 from 116°Ls to 325°Ls. If we restrict ourselves to the period where the apparent diameter >/=20", it proceeds from 224°Ls to 273°Ls. The thawing south polar cap (spc) will be easily caught if not obscured by a possible dust disturbance. It really overlaps with the season of dust storms.
The observations of the spc should be started earlier. Its largest substance will pop out under from the complex south polar hood (sph) before the arrival of the southern vernal equinox 180°Ls (before around 5 May). The central latitude reads then 17°S, and so it is easily observable. It will soon start to thaw, and we should watch the centre of the spc whether any shadowy area or scar is seen inside the cap or not before 200°Ls (cf CMO #115 p1004). Notable is that from 230°Ls to 240°Ls, some part of the spc melts more rapidly than the rest, and the centre of the spc will deviate from the south pole, and so we should be attentive to the region at the beginning of August. A depressive area called Novus Mons will also be seen brighter around from 180°Ls inside the spc and will be detached from the spc around at 250°Ls. It will be completely a detachment near at the end of September, as the southern summer solstice (270°Ls) visits, and also a minimal state of the spc will be attained.
As mentioned above, the season of dust storms will come when the apparent diameter is sufficient. There arise a lot of local dust disturbances every season especially when the polar cap is at the stage of thawing or sublimation. These are not however the so-called dust storms. The dust storms are those caused by clouds that rise high up into the atmosphere and influence the meteorology. Note that in the case of the 1988 great apparition there were not occurred any dust storm. However in the case of the 1971 great apparition, a sharp and great dust emergence started at 260°Ls. That was great, encircling, and global. In 1956 also, we had a great dust cloud occurrence at 250°Ls, and it encircled the southern hemisphere (not known about the deep northern hemisphere, and hence can not be said global). In 1924, E M ANTONIADI et al recorded that the Martian surface was totally crème yellowish just like the Jovian surface at 236°Ls. Any of these seasons fall in our scope in 2003. The dust cloud we met in 2001 was the one labelled global, great and major within a week, but started mildly much earlier than those noted above at 185°Ls. It will be our pressing work in 2003 to watch the planet carefully from 180°Ls to compare the result with the records we secured in 2001 (if there will not start a global dust storm). It is the morning limb that should be attentively observed.
The dust storm is related with a higher atmosphere, but has a potential to cause other secondary local dust clouds, and these sometimes cause movements of sands on the surface and bring some secular changes of the dark markings. It is thought the Dædalia dark patch in 1973 and the Ætheria dark patch in 1975 were given rise to in this way. It is suspected that some local dust devils caused by the 2001 long standing mother yellow cloud might have left several singular markings. The following are the area to be watched: Around Solis L to Dædalia, the east of Syrtis Mj, the Ætheria dark patch, the western end of M Sirenum, inside Noachis, and the dark area from M Cimmerium to M Tyrrhenum.
One of the biggest observations in 2001 was the prediction and the demonstration of the spontaneous flares at Edom by the DOBBINS-PARKER team. The Edom area must be out of scope in 2001, but the area of Solis L at the beginning of August may come into the next scope (as S FUKUI et al observed in 1958), as to which MURAKAMI will write an essay soon in this series.
From the terrestrial Northern Hemisphere, the lateral altitude of the planet will be still low in the height of the 2003 Martian season (though higher by 10 degrees than the annoying altitude met in 2001). Especially its apparent declination will be down nearly to -23° from the end of February to April, and so it will be hard to get any good seeing condition from our side. We however expect to receive good observations from Australia, Singapore and Okinawa (oh don't forget Tenerife!).
On 2 May, the planet will attain the western quadrature along the RA (see the footnote at the end of this article), and thereafter we can observe the planet at the meridian (first in the morning, gradually moved to midnight as summer comes).
As is well known, the rotation period of Mars is longer than that of the Earth by 40 minutes, and the longitude of the CM augments 10 degrees by 40 minutes, and hence if we observe every day at the fixed times every 40 minutes, we can obtain a series of documents that will be useful to compare at the same LCMs and provide an important trend of daily as well as seasonal changes. The yellow cloud event in 2001 proved how this way was efficient, and also left further lessons.
Any ccd observation should always be accompanied by the blue ingredient. It is not for the false detection of 'blue clearing' (that should be subject to Ockham's razor), but for the detection of the distribution of the white mists. The observation of vapour configuration is decisive to the observation of the Martian season even when the dust prevails.
It is tedious to calculate all the elements of the ephemerides for each observation. We however need at least the following five elements; LCM=ω,
the central latitude De=φ,
the apparent diameter =δ,
and the phase angle =ι .
We otherwise don't necessarily use Ds because the season is designated by Ls. In the CMO, we shall hereafter use the letter λ as the areocentric longitude of the Sun like λ=180°Ls (as approved in the CMO INA Meeting). The phase angle easily (though roughly) gives a ready hint of the position of the longitude at noon.
Every numerical value should be rounded off discarding the decimal figures (except for δ). It's foolish to denote like Ls=180.12°. If anyone ever produced a physically different image at 180.1°Ls from that at 180.2°Ls, please tell us. As well, how can you write as ω=180.0°W if you are not really confident that the image is really different from ω=179.9°W?
(*Note): Our Quadrature is here defined as a 90 degree difference of the planet from the Sun along the Right Ascension: The Western Quadrature in this sense attains on 2 May as seen from the fact how far Mars (whose RA=20h34m55s at 00:00GMT) is ahead of the Sun (RA=02h35m04s at 00:00GMT). Usual definition of the Quadrature makes use of a 90 degrees elongation along the Ecliptic longitude. In this sense the Western Quadrature occurs on 18 April 2003 at 11h.