More spacecraft on Mars

Beagle 2 landed in Isidis Planitia (telescopic Isidis Regio) on Christmas morning 2003. Earlier, the Director had kept Prof. Colin Pillinger and his team up to date with day by day news of the large regional dust storm in the southern hemisphere of the planet (see below). There had always been the danger that a resonant dust cloud would have arisen over Isidis, but – as the writer predicted – it did not occur. Unfortunately no signal was ever received from Beagle on the planet’s surface. At a Press Conference Prof. Pillinger quoted the Director’s view that the probe had not been blown off course by a dust storm. (More likely it crash-landed as a result of some malfunction.) This does not diminish the success of the ongoing Mars Express mission of which Beagle represented but one part. The orbiting craft will continue a programme of high-resolution photogeology, conduct a search for subsurface water ice and perform mineralogical mapping. Early results are spectacular. We hope there will be a Beagle 3.

      The safe landing of NASA’s twin rovers Spirit (on January 4 in Gusev crater in western Memnonia; –15 deg, 176 deg) and Opportunity (January 25, Meridiani Planum (telescopic Meridiani Sinus; –2 deg, 354 deg.)) coincided with the announcement by President George Bush that the United States intends to carry out a manned Mars mission (albeit dependent upon first establishing a permanent base upon the Moon). This announcement, in the spirit of President Kennedy’s famous promise that man would reach the Moon within the decade of the 1960s, sets a worthy second millennium challenge to mankind. Meanwhile, in addition to providing realistic eye-level imagery, the twin rovers will analyse rocks and soils using various spectroscopic techniques.

BAA observations

General

This sixth and final report for the present apparition covers the period 2003 December 1 (D=11.0 arcsec; Ls=308 deg.) to 2004 February 15 (D =6.2 arcsec., Ls=350 deg.) The planet’s declination changed from –4 deg. to +15 deg, and the sub-Earth latitude varied from –25 to –19 deg.

South Polar Cap

 
The SPC has remained visible, though it was for a time apparently obscured by the regional dust storm described below. By January it was very hard to see visually on the tiny disk, but on the 18th Don Parker caught it visually with a power of 700x, and Damian Peach just managed to image it as late as January 27 as a nearly dimensionless point. By February 2 it seemed that the S. polar hood was forming.

      The Director obtained over 150 drawings to date during this apparition. He measured the latitude of the N. edge of the SPC on the best ones between 2003 May 10 and December 18 (Ls = 183–318 deg.), and plotted latitude as a function of CM longitude. The resulting ‘polar spiral’ nicely shows the recession of the cap, though some scatter is inevitable with visual data. (Some averaging of points has been done to avoid overcrowding.) It may be compared with results for 1988 (Ls = 232–281 deg.) published in the Journal, 99 (2), 52–53 (1989). No attempt has been made to map interior details or detached parts of the cap.

SPC latitude as a function of CM longitude plotted for martian southern spring and summer, after drawings by R.J. McKim. The outermost point of the polar spiral is at Ls = 183 deg, and the innermost at Ls = 318 deg. Dots (Ls = 183–202, 230–245, 271–
291 and 316–318 deg.) and crosses (Ls = 203–211, 250–269 and 292–306 deg.) are used to denote alternating circuits of the pole.

Regional dust storm, 2003 December–2004 January
 

On December 13 ( Ls = 315 deg.) Parker took CCD images which showed that a significant dust storm had arisen over southern Chryse (telescopic southern Xanthe) and the eastern part of Valles Marineris. Smaller, secondary dust cores were seen in northern Argyre and over Aram. (It seems that this really was the first day of the storm.)

      By December 13/14 a band of dust had extended SW from Argyre to higher latitudes and westward across Thaumasia to the south of Solis Lacus (with the latter feature somewhat obscured). There was a general expansion of the original cloud to veil Eos–Aurorae Sinus–Mare Erythraeum. On December 15/16, further images showed a belt of dust crossing Noachis and Pandorae Fretum–Deucalionis Regio diagonally from Argyre, and impinging upon Sinus Sabaeus. (Indeed, the Meridiani Sinus area was later affected by dust for a time.)

      By December 17/18, activity was observed in Hellas in the form of a secondary bright core in the vicinity of the NW of the basin, its deepest part. However, the dust did not develop any further, probably having reached its maximum extent on this date. Observing visually, the Director (December 17 and 18, 41-cm Dall–Kirkham Cassegrain, x410) detected a small projection of part of the Noachis dust cloud beyond the morning terminator.

      A series of images by Ed Grafton at similar CML nicely demonstrated the progressive decline of the E. end of the storm during December 18–21. By December 22 little suspended remained over Noachis, and the NW Hellas dust core was smaller and weaker. On the same date, images by T.Akutsu (CML = 63–85) showed that the W. end of the activity had significantly declined, with the very little remaining dust in E. Thaumasia connected to a bright persistent core in Argyre. Solis Lacus was again dark and well defined.

      In mid-January images continued to show small patches of dust around Aurorae Sinus and over Argyre. On January 16 Damian Peach, and on January 24 Martin Taylor and the Director, found the Hellas basin normal in red light and free from dust.

      There were several albedo changes associated with the storm, though the affected areas were once again normal by mid-January. The Pandorae Fretum area looked for a time broader and darker, and Noachis was somewhat less bright than before the event. The terrain about Depressiones Hellesponticae (which marked the southern boundary of the Noachis dust) became much darker than before. A similar albedo change occurred at the time of the planet-encircling dust storm of 1956, and more recently during the S. hemisphere regional event of 1988 November (see below).

      The general E–W extent of the storm at maximum was similar to that mapped by the writer for the 1988 November event (which had begun in Thaumasia to the south of Solis Lacus at Ls = 313). However, in 1988 the activity ultimately did not quite extend as far east as Hellas. In its initial development, the present event began more like the regional storm of 1990 November at Ls = 326. The Director actually cannot recall any historical event beginning in the location of the present one (S. Chryse–Xanthe/E. Valles Marineris) which showed such a considerable expansion in longitude, or which was of such long duration. (Both the 1988 and 1990 events are illustrated and charted in the writer’s Telescopic Martian Dust Storms (Mem. Brit. Astron. Assoc., 44 (1999). The Director (in BAA E-Circular No. 127) predicted that the event would not exceed regional status. This prediction was based upon the fact that the seasonally latest encircling storm ever observed had begun at Ls = 311 (in 1924 December).

Concluding remarks

 

Although a few observers continue to observe the planet successfully with the larger apertures, it is not anticipated that there will be a need for a further interim report prior to solar conjunction on September 15. A more complete analysis will be prepared later. Mars will next be in opposition on 2005 November 7.