Mars in 2002–03

First interim report

This report was published in the BAA Journal for 2003 June

General

The great perihelic opposition of 2003 has begun! Mars was in conjunction with the Sun on 2002 August 10. The observations received since then cover the period 2002 October 7 (Ls = 78 deg., D = 3”.6, tilt = +26 deg. N.) through till the date when this report is being compiled, 2003 April 20 (Ls = 171 deg., D = 8”.6, tilt = –14 deg. S.). Thus the end of the S. hemisphere autumn season on Mars (N. hemisphere spring) and most of S. winter (N. summer) have been covered so far. Observations made in the UK were contributed by D. Gray, C. Proctor (CCD) and the Director. Overseas contributions – all CCD work apart from visual observations by M. Frassati (Italy) – came from P. Campbell (USA), T. Ikemura (Japan), D.C. Parker (USA), D. Peach (during a stay of several months on Tenerife), C. Pellier (France) and M.P. Valimberti (Australia). Bulletins detailing Japanese work were sent by the OAA. The Philips ToUcam Pro webcam seems to have become a popular tool for CCD imaging since the last apparition. In the following report only the BAA work is described and illustrated, without reference (on this occasion) to ongoing work by active spacecraft in martian orbit.

Surface features

Following the planet-encircling dust storm in the 2001 apparition (R.J.McKim, J. Brit. Astron. Assoc., 112(3), 119–121 and 123 (2002); see also the images reproduced in the Report of the BAA Ordinary Meeting of 2002 September 21, ibid., 113(2), 112 (2003)), several albedo changes were noticed. The Solis Lacus became smaller, with the long axis differently oriented, and Nectar disappeared under dusty surface deposits. West of Solis Lacus the north–south curved streak named Phasis reappeared, resembling its form during 1877–79. Syrtis Major appeared thinner, and a possible new albedo feature in Aethiopis was imaged by Peach in 2003 March. Which changes would persist into 2003?

Recent images by Parker show that Phasis remains visible, though it is fainter than after the 2001 dust event. Syrtis Major had already returned to normal width by the start of the apparition. Solis Lacus looks normal, large and dark, but more observations of these longitudes are wanted. The small albedo feature in Aethiopis has not been recovered. Several longstanding albedo anomalies, such as the Aetheria darkening, and the pattern of the markings in the Casius–Nodus Alcyonius area, remain well visible. Cerberus remains faint.

Further changes since the end of the last apparition are also evident in the present appearance of the area between Mare Sirenum and Aonius Sinus. This appears as a continuous dark belt, actually a characteristic feature of late southern spring on the planet. A similar appearance was noticed in 1939 and 1986, for example. Another current feature is the great breadth and darkness of Depressiones Hellesponticae adjoining the bright S. polar hood. Hellespontus and Yaonis Fretum are dark streaks marking the western edge of Hellas.

Recent images (south at top). Top row, left–right. Images by Damian Peach with 30.5-cm Schmidt–Cassegrain at f/29, and ST-5c CCD camera. 2002 December 10d 06h 39m, CML = 36 deg.; infrared filter (800–1200 nm); Mare Acidalium is prominent, and the NPH is present; D = 4”.2 (!). 2002 December 30d 07h 28m, CML = 213 deg., infrared filter; a bright Elysium fringed by a pale Cerberus and dark Propontis and Aetheria. 2003 January 2d 07h 02m, CML = 178 deg.; infrared filter; notice the bright Nix Olympica near the evening terminator. 2003 January 28d 07h 04m, CML = 286 deg.; infrared filter; Syrtis Major broad; Hellas light; tiny NPC. Bottom row, left–right: Filter images by Don Parker with 42-cm reflecter at f/55, and ST9XE CCD camera: 2003 March 30d 10h 52m, CML = 111 deg.; red light (RG610 filter; 610–1100 nm); dark band from Aonius Sinus to Mare Sirenum; Solis Lacus dark; Phasis imaged. 2003 April 16d 10h 20m, CML = 300 deg; red light (RG610 filter); large, bright SPH; many fine details around N. tip of Syrtis Major and around the dull Hellas. 2003 April 16d 10h 32m, CML = 303 deg.; green light (531 nm); Libya evening cloud. 2003 April 16d 10h 27m, CML = 302 deg.. blue light (450 nm); strong ‘blue clearing’. D = 8”.4 for this tricolour set. (Colour composites were also contributed by both observers.)

Atmospheric activity

Many records of white clouds are to hand. For instance, as early as 2002 October 24 under CML = 133 deg., Gray described Nix Olympica as ‘sparkling’ and bright, and Peach imaged it as a bright patch at the evening terminator on 2003 January 2. On November 18 Gray found Hellas to be light on the morning side, while on December 18 it appeared bright to him in the afternoon. Frassati shows it bright on the morning side on 2003 February 1. Further examples in this incomplete listing: 2003 January 7, the Director found Elysium bright at the morning limb, and on January 18 Argyre looked bright to Frassati. Other bright clouds were seen over Candor, Chryse–Xanthe, Libya, etc., etc., from time to time. Parker recently imaged strong surface features in blue–violet light: a ‘blue clearing’ of order 2, on April 16 in the longitude region of Syrtis Major–Sinus Sabaeus.

No current dust storm activity is evident in the Section’s observations, and Hellas is currently dull. But a very careful watch should now be kept for major dust activity through till the end of the apparition. The 2001 planet-encircling event began at an unusually early time in the martian year, at Ls = 185 deg., just after the S. spring equinox (corresponding to 2003 mid-May in the present apparition). Any positive observations should be reported at once.

The polar regions

Circumstances prevented all but the closing stages of the NPC recession from being observed. In the earliest observations the N. polar cap was still visible, but very good seeing was needed to make it out upon the tiny disk. A CCD image by Peach on 2003 January 28 (Ls = 129) shows a small ground cap (having reached the static summer remnant by that stage), and the NPC may also feature as a tiny spot on an image by Parker on April 11 (LS = 166). In the late northern summer the polar area was often covered by a whitish hood. In the 1982 and 1984 apparitions, according to BAA data, the hood appeared to mask the NPC from about Ls = 152–161 deg.

At present the S. polar hood is a large brilliant area covering the southern limb. BAA data shows the SPC to have been hood-free by about Ls = 172 deg, at the 1988 opposition, though not all longitudes were uncovered simultaneously.

The Section web site

At the November meeting of the Council, the Director appointed Bob Marriott – who is also our Curator of Instruments – to manage a new Mars Section web site. We thank Prof. Jim Bell of Cornell University, USA, for hosting the site from 1997. The move to the new site will take place in early June, and the site will be linked from the main BAA web site.

Recommended reading

A new guidebook for the Red Planet has been written by Meteor Section Director Neil Bone (Philip’s Mars Observer’s Guide, Philip’s, 2003) and recently published. It will be of interest to all Section members and to intending observers. The Director contributed some illustrations and the Foreword. New observers should also familiarise themselves with past Reports of the Mars Section to appreciate the type of work that can be accomplished with different apertures. For martian nomenclature see the general map in J. Brit. Astron. Assoc., 113 (2), 70–71 (2003), and the standard maps reproduced in the Director’s Telescopic Martian Dust Storms, Mem. Brit. Astron. Assoc., 44 (1999).

Finally, Colin Pillinger, in a recent letter, informs me that he and his wife Judith are writing a book comparing the voyage of Beagle II with that of the original Beagle of Captain Fitzroy and Charles Darwin.

Richard McKim, Director