Mars was particularly close to the Earth in 2003, for the opposition – on August 28 – occured with Mars almost exactly at perihelion. The planet’s disk diamter at closest approach (actually one day before opposition, when Mars was 0.37272 astronomical unit distant) was 25.11 arcseconds. In fact, the 2003 opposition was the closest one ther had been in thousands of years nad the closest Mars will be for many more years to come.
Mars’ unusually large apparent diameter allowed even those observers with small telescopes to detect considerable amount of detail on the planet’s surface. This report is based on the observations submitted by the following:
- Stephen Brincat of San Gwann captured images with a CCD camera attached to a Meade SSC-10 (25.4-cm Schmidt-Cassegrain) telescope;
- Joseph Caruana of Ghajnsielem. Gozo, observed with his Celestron Nexstar 8i (20.3cm Schmidt-Cassegrain) telescope and colour filters;
- Charles Galdies of Naxxar used a 25.4cm Newtonian reflector and filters;
- Vincent Zammit of Kirkop obtained images with a webcam attahed to his 20.3-cm Newtonian telescope and 3X Barlow lens
The observations extended form May 25 to September 23 covering most of spring in the southern hemisphere of Mars. The southern hemisphere was favourably presented to Earth this apparition, the tilt of the planet’s axis being -19deg at opposition.
A total of 48 drawings and photographic images were submitted, together with intensity estimates of Martian features and many descriptive notes. This report describes the retreat of the South Polar Cap and the surface markings recorded.
The South Polar Cap
The South Polar Cap was a prominent feature of the planet early in the period under review, when it was described as rather large and brilliant. It shrunk slowly during the second half of August and September, due to the gradual warming of Mars’ southern hemisphere as Summer approached there.
The cap exhibited a dark border which sometimes merged into the dark areas of the south polar regions, particularly towards Hellespontus. A considerably darker portion in the cap border was observed in the region of Thyle I. Joseph Caruana found that a light green filter (Wratten #56) accentuated the contrast between the Polar Cap and surrounding areas. As the cap retreated its well-known axial asymmetry developed.
Mare Cimmerium was dark. A slightly darker area on its norhtern edge was evident in late July and early August. Electris, Eridania and Ausonia were almost equally bright. Xanthus was seen as a thin, dusky band separating Eridania and Ausonia. The large ,bright areas Zephyria, Elysium and Aethiopis to the north of Mare Cimmerium were all featureless. Hesperia appeared as a light rift between Mare Cimmerium and Mare Tyrrhenum. The eastern end of Mare Tyrrhenum was blunt and dark. Syrtis Minor was also dark, as was Mare Hadriacum futher south.
The hemisphere of Mars centred on Syrtis Major was favourably placed for evening viewing form Malta around opposition. It was well documented, as can be seen from the photographs and drawings presented in the following pages. The large basin Hellas was seen as a light patch separating lapygia from the South Polar Cap. Syrtis Major was a very dark and well-pronounced feature. it was quite broad nad blun-ended to the north. lapygia was a bit lighter than the Syrtis. Hellespontus appeared as a faint streak, curving and tapering southward from lapygia.
Mare Serpentis was very dark too. Deucalionus Regio was light, and Sinus Sabaeus was generally dark, but weak and narrow at its western end. Sinus Meridiani appeared as a dark blob at the western end of Sinus Sabaeus. Margarifiter Sinus and Aurorae Sinus were seen as dark shadings within ht elarge rectangular area containing also Mare Erythraeum, which itself was lighter. Argyre I and Chryse were prominent and light coloured. Oxia Palus appeared as a streak issuing from the Northern tip of Margaritifer Sinus into the Oxia and Eden regions. Niliacus Lacus and Nilokeras appeared as a broad shading close to the planet’s southern limb. The areas surrounding Solis Lacus were also well observed. The Lacus itself was one of the darkest features of Mars, and appeared more or less round. Nectar. Thaumasia and Foelix appeared as dusky ‘bridges’ joining Solis Lacus to Bosporos Gemmatus and Aonius Sinus. The regions Bosporos, Pointica Depressio and Aonius Sinus appeared as homogeneous shades, but darker than the great Mare Australe further south. Mare Sirenum was broad; it exhibited a darker band along its northern edge. The great norhtern deserts Tharsis, Memnonia, Mesogaea and Amazonis were bright and featureless, though ill-defined shadings were detected under good observing conditions. The Propontis Complex appeared as a number of dusky arcs close to the planet’s northern limb.
Estimates of the intensity of Martian surface features were made by Charles Galdies using the Association of Lunar and Planetary Observers’ scale of 0 = the black sky background and 10 = the brightness of the South Polar Cap. The estimates of the most prominent features are given in the table next page.
The planet’s atmosphere has been largely dust-free, despite perihelion passage (August 30. 2003) and the approach of southern summer solstice (Septemberr 29. 2003). On August 20, Charles Galdies saw distinct brighter areas over Hellas with a blue filter (Wratten #38A). A morning cloud was photographed by Vincent Zammit on September 7 northeast of Solis Lacus.