Forthcoming 2005 Mars
(2)

 

Mars in 2005

Masatsugu MINAMI, Masami MURAKAMI and Akinori NISHITA


1

 

The 2005 Mars, its angular diameter δ being 4.2 arcsecs at the beginning of 2005, is predicted to be closest to the Earth on 30 October 2005 (at 3:26 GMT la J Meeus) with the maximal angular diameter of δ=20.17 arcsecs as follows:

 

closest 30 October 2005 at 3.5h GMT

λ   315.2Ls

φ   14.3S

δ    20.17"

magnitude - 2.3 degrees

distance  0.46406 au

69.42 million km

Position (RA: 03h02m, App Decl: +1614' (2000.0))

 

The closest distance in 2003 was 0.37272 au or 55.76 million km, and so this year the closest planet is more away by about 14 million km.

 

The opposition occurs this year after the perihelion, and so after the day the planet is closest: The planet will thus be at opposition on 7 November at 8h GMT with Apparent Decl=+1554'.

 

The rate of increase of the angular diameter at the first half of the year is rather slow, and it is not until mid-July that δ reaches 10 arcsecs. After opposition, the diameter will decrease rather rapidly and goes down to δ=12.2" at the end of 2005.

 

 

When the planet is near at opposition, it will shine in Aries so that its apparent declination is near +16 as noted above and so the altitude of the shining Mars at meridian is higher by about 30 than that of the 2003 planet when it was closest if seen from the standpoint of the observers in the northern hemisphere. We shall repeat, but the approach during the first half of 2005 is more asymptotic or slower until the altitude of the planet in the northern sky will become more favourable. In early February, it shines very low around with App Decl= -24 at Sagittarius, and then the planet will cross the celestial equator from south to north at the end of June, and further ascends northward to +5 at Pisces in summer, and will pass the western quadrature on 12 July. The apparent diameter δ, after it passes δ=4.2 with λ=137Ls at the beginning of 2005, gradually reaches δ=10 around 14 July; and so we may say the first favourable time for the northern observers would come in mid-July. The Martian season λ in mid-July is near 250Ls where Ls denotes the Areocentric Longitude of the Sun. Somewhat by coincidence, it is the season when the 2003 Mars was near at opposition. Furthermore it is the memorial time when the 1956 global dust storm was entrained. The apparent diameter then reaches δ=15 around on 10 September. The data in 2005 are thus made into a Table.

 

Western quadrature

12 July

δ=10.0

λ=247Ls

at perihelion

17 July

δ=10.3

λ=250Ls

Stationary

1 Oct

δ=17.8

λ=298Ls

closest approach

30 Oct

δ=20.2

λ=315Ls

Opposition

7 Nov

δ=19.9

λ=320Ls

Stationary

12 Dec

δ=15.1

λ=338Ls

 

 

Here we shall go in some details to compare the Martian season and the status of the 2005 Mars with those in 2003 and /or 2001.

 

As is suggested by the Figure at the left-hand side, the maximal δ (=20.2) in 2005 corresponds to the angular diameter we experienced in 2003 around on 20 July and/or on 3 October, and so we may say the 2005 apparition is similar to the 2003 case where a period of about 2.5 months from the latter part of July 2003 to the beginning of October 2003 are completely missed. The diameter of 20.2 arcsecs implies to be smaller than the maximal diameter in 2001, but it is still larger than the case in 1999. The above figure suggests however another important characteristic of the 2005 apparition to be noticed: the peak of the diameter comes quite at different Martian season. The apparent diameter δ in Fig 3 is a function of the Ls, and so apparently the 2003 Mars showed us well the surfaces of Mars before the summer solstice of the Martian southern hemisphere (λ=270Ls), while the 2005 Mars will provide us the season from the southern summer solstice to southern autumn equinox (λ=360Ls (=000Ls)). At opposition the 2005 Mars will attain the season of λ=315~320Ls, so that we can watch better the seasons around this λ=310~325Ls, while in 2003, this season visited in mid-December so that the δ was less than 10 arcsecs. So from the point of view of observing the Martian season, the 2005 apparition is very supplementary and our continuation of observations is indispensable.

 

It is also interesting to notice the intersection point of the 2001 and the 2005 graph. It is near the perihelion, and this implies that we can observe the season at λ=250Ls in 2005 under the condition similar to that in 2001. Just the defect of illumination must be at the opposite side. We thus say we can observe the season symmetrically three times successively in 2001, 2003, and 2005.

 

2

 

As stressed in the preceding section, it is absurd to regard the 2005 apparition is inferior to the 2003 apparition. They are both equally important with respect to the observations of the Martian seasons, and in some respects the 2005 Mars shows unrivalled points.

  

As suggested, the apparent diameter δ becomes larger than 15 arcsecs around 8 September 2005 when the season λ reaches 284Ls. Since our recent Martian observations aim at the Martian meteorology as a function of the season, this value implies something dividable.

 In 2003, δ proved to have been already near 16.1 arcsecs when the Martian season attained 286Ls. The δ was further down to 15 arcsecs when the season reached λ=290Ls, so that in 2005 from around λ=290Ls, the 205 Mars will surpass the conditions in 2003.

On 30 October, when δ=20.2, the season reaches λ=316Ls as repeatedly noted, but in 2003, at λ=316Ls the δ was no larger than δ=9.8". The season λ=290Ls will arrive on 17 September, and the day is the beginning of new era.

 

The south polar cap (spc) is already at the minimal state at λ=290Ls. The 2005 apparition provides the last opportunity in the present cycle to be able to observe the total regions of the southern hemisphere: In fact, after March 2005, the tilt of the north pole will go away from the Earth and the central latitude φ (=DE) keeps φ=14S even when the planet is near at opposition. So this is the best chance to watch the final/residual state of the spc beyond λ=310Ls. It should be remarked that after λ=235Ls (around at the end of June in 2005) the centre of the spc will deviate from the south pole towards the direction of Ω030W, and the appearance of the final state of the spc is variable according as the CM varies.

 

There are several phenomena characteristic or just observable in the season which we encounter in 2005. For instance the minute aftermath of the detachment and vanishing of Novus Mons is a subject of observation. At the same time of the observations of the inside of the spc as well as its periphery, the high latitude continents and dark markings should be carefully observed: For example in 1990 the region of Hellas showed a strange light and shade partly misted during the period λ=320~330Ls. Eridania also behaved interestingly in 1990. Interesting is also the observation of the Tharsis ridges and Olympus Mons when they are in the afternoon. The evening orographic cloud over the summit of Olympus Mons ceases to be active around from λ=200Ls (in 2005 around on 26 April), but the three Montes at Tharsis are different (also different among them), and the cloud over Arsia Mons continues to be active and makes another smaller peak from λ=250Ls to λ=330Ls, namely the period when the planet is before and near at opposition. The Arsia white cloud was not observed at this season in 2001 because of the presence of the yellow cloud. So the white cloud must be sensitive to the mixture rate of condensate and dust. The summit of Olympus Mons should be watched carefully when it becomes near the terminator or limb. These should be checked by the use of the genuine Blue filter.

 

Even if the season after λ=290Ls is very own with respect to 2005, we should also pay our careful attention to the season before that because the Martian season is not a simple repetition. The time of occurrence of the dust clouds is different from year to year, and we should be on alert concerning the yellow cloud around from λ=200Ls (at the end of April) though δ is still smaller with 6.5". The spc begins to thaw rapidly around from the time.

Rather unfortunately, the 2005 Mars will not provide well the information about the north polar region (npr), but we should pay attention to the activity of the north polar hood (nph) in relation with some possible dust disturbances. It was reported in 2002 the MGS cameras caught several dust outbursts near the northern high latitude region during the very season from λ=315Ls to λ=350Ls (http://www.msss.com/mars_images/moc/weather_reports/ ). In this sense, M Acidalium and Utopia are the regions attentively watched in 2005: As well Chryse and the area from Neith R to theria are the important gates concerning the npr dust/condensate cloud information. Since Chryse played frequently a special role in entraining the dust disturbances in 2003 (especially the December 2003 significant dust occurred at λ=315Ls), we should be attentive about this particular region.

 

The last but not the least, we should call attention a bit to a possibility of the reflection flare occurrence in 2005. The 2005 Mars is akin to the 1958 case, and so the Solis L area is still a candidate. Geometrically the coincidence of DE and DS will occur around 8 November when the apparent diameter is still of δ=19.9". Refer to a detail in another article which we shall translate soon from the Japanese edition.

 

 

3

 

Finally we try to mention about the observation cycle and stress that the observation of the Martian season is now a principal object of the Martian observations.

 

The planet Mars approaches to the Earth every two years and two months and then away, and every apparition the planet shows us a different season in Ls to us with a different maximal diameter. So in order to observe the whole Martian season in a favourable condition it will need exactly seven times of apparitions or 15 or 17 terrestrial years. During the period, there are several apparitions where the maximal angular diameter is below 15 arcsecs, and in those periods we (the northern observers) are under the cold winter season. However these apparitions also are important for us to gather the data about the seasonal meteorology on Mars.

 

Yes the present day observation of Mars is for the observations of the atmospheric phenomena on Mars and nowadays the effort just to detect the details on the Martian topography has been very out of date. However it is important for the observers to be acquainted with the fundamental dark or bright markings on the planet since the diurnal variations and/or the annual variations, and/or furthermore the secular changes can be observed with reference to the fundamental marking configuration on Mars. In any scientific work, repetition or comparison is a key word: the true difference (or even differentiation in mathematics) can be established based on a rigid comparison (or a reference frame in mathematics) and if the comparison frame is fragile, any assertion cannot be proved. In real observations of Mars, the repeated comparisons of the surface with the same surface on the preceding days are the least requirement of the wise observations. A repetition day by day of observing the same surface from the same angle, even if boring, is one of fundamentals.

 

If one wishes to compare the surface on the day with the surface appearance of the day before one should have prepared the observation 40 minutes earlier than the day before. Conversely speaking to find the same surface as the surface one observed the day before, one have only to observe 40 minutes earlier than the time one observed the day before, because the rotation of Mars is longer than the rotation of the Earth by about 40 minutes (exactly 41.3 minutes longer, while the rotation of Mars is 24h37m26s: more exactly speaking we must further take account of the every-day mutual motions). If we repeat this consideration, we are easily led to the following axiom: To prepare the documents enough to cover all the cases, we should observe every 40 minutes every day at fixed times. The planet rotates nearly 10 degrees every 40 minutes, and so if we observe every 40 minutes, we are to have a series of images each of which are separated by 10 degrees and its multiples. The following tables show how we shall get the series of ω (=Longitude of the Central Meridian) by the every 40 minute observations.

 

LCM seen from Asia and Oceania

GMT

12:20

13:00

13:40

14:20

15:00

15:40

16:20

17:00

17:40

18:20

19:00

27 Oct

068W

078W

088W

097W

107W

117W

127W

136W

146W

156W

166W

28 Oct

059W

069W

079W

089W

098W

108W

118W

128W

137W

147W

157W

29 Oct

050W

060W

070W

080W

089W

099W

109W

119W

128W

138W

148W

30 Oct

042W

051W

061W

071W

081W

090W

100W

110W

120W

129W

139W

31 Oct

033W

043W

052W

062W

072W

082W

091W

101W

111W

121W

130W

01 Nov

024W

034W

044W

053W

063W

073W

083W

092W

102W

112W

122W

02 Nov

015W

025W

035W

045W

054W

064W

074W

084W

093W

103W

113W

03 Nov

006W

016W

026W

036W

045W

055W

065W

075W

085W

094W

104W

04 Nov

358W

007W

017W

027W

037W

046W

056W

066W

076W

086W

095W

05 Nov

349W

359W

008W

018W

028W

038W

047W

057W

067W

077W

086W

06 Nov

340W

350W

360W

009W

019W

029W

039W

048W

058W

068W

078W

07 Nov

331W

341W

351W

001W

010W

020W

030W

040W

049W

059W

069W

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LCM seen from Europe

GMT

21:20

22:00

22:40

23:20

00:00

00:40

01:20

02:00

02:40

03:20

04:00

27 Oct

209W

218W

228W

238W

248W

257W

267W

277W

287W

296W

306W

28 Oct

200W

209W

219W

229W

239W

249W

258W

268W

278W

288W

297W

29 Oct

191W

201W

210W

220W

230W

240W

249W

259W

269W

279W

289W

30 Oct

182W

192W

202W

211W

221W

231W

241W

250W

260W

270W

280W

31 Oct

173W

183W

193W

203W

212W

222W

232W

242W

251W

261W

271W

01 Nov

165W

174W

184W

194W

204W

213W

223W

233W

243W

252W

262W

02 Nov

156W

166W

175W

185W

195W

205W

214W

224W

234W

244W

253W

03 Nov

147W

157W

166W

176W

186W

196W

206W

215W

225W

235W

245W

04 Nov

138W

148W

158W

167W

177W

187W

197W

206W

216W

226W

236W

05 Nov

129W

139W

149W

159W

168W

178W

188W

198W

207W

217W

227W

06 Nov

121W

131W

140W

150W

160W

169W

179W

189W

199W

208W

218W

07 Nov

112W

122W

132W

141W

151W

161W

170W

180W

190W

200W

209W

 

 

LCM seen from America

GMT

05:20

06:00

06:40

07:20

08:00

08:40

09:20

10:00

10:40

11:20

12:00

27 Oct

326W

335W

345W

355W

005W

014W

024W

034W

044W

053W

063W

28 Oct

317W

327W

336W

346W

356W

006W

015W

025W

035W

045W

054W

29 Oct

308W

318W

328W

337W

347W

357W

006W

016W

026W

036W

046W

30 Oct

299W

309W

319W

329W

338W

348W

358W

007W

017W

027W

037W

31 Oct

290W

300W

310W

320W

329W

339W

349W

359W

008W

018W

028W

01 Nov

282W

291W

301W

311W

321W

330W

340W

350W

360W

009W

019W

02 Nov

273W

283W

292W

302W

312W

322W

331W

341W

351W

001W

010W

03 Nov

264W

274W

284W

293W

303W

313W

323W

332W

342W

352W

002W

04 Nov

255W

265W

275W

284W

294W

304W

314W

324W

333W

343W

353W

05 Nov

246W

256W

266W

276W

285W

295W

305W

315W

324W

334W

344W

06 Nov

238W

247W

257W

267W

277W

286W

296W

306W

316W

325W

335W

07 Nov

229W

239W

248W

258W

268W

278W

287W

297W

307W

317W

326W

 

As seen, since the rotation period is irrational, the degrees slightly deviate after a while, and hence every week we should adjust the observing time. In the above cases, if one wishes to obtain the surfaces which one saw five days before, one should shift the observation times by 20 minutes. After about 40 days or about 20 degrees in Ls, the similar surface come around to recur, and it is good again if one could obtain a series of the surfaces with the same longitudes to compare.

For the ccd imagers, the span of 40 minutes from one shot to the following looks too long. If so, one can take the surface pictures every twenty minutes. In this case one can get two series of images to be compared. Furthermore, since such a phenomenon as the movement concerning the polar hood or the polar dust is rapidly variable and so these cases demand a shorter span observations, the every 20 minute observations are recommended.

(December 2004)


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