2003 Mars Report from Cooperative Observation Networks. II. After the Opposition

Abstract

This is the second report on Mars in 2003 by two networks for cooperative Mars observations in Japan: Nishi-Harima Astronomical Observatory Mars Cooperative Observation and Association of Lunar and Planetary Observers in Japan. This paper is a summary of 4145 data for 226 nights collected by the two networks during the second half of the last apparition from 2003 September 1 through 2004 June 22, corresponding to a period of $L_{\mathrm{s}} \sim 252 {{}^{\mathrm {\circ }}} \hbox{--} 51 {{}^{\mathrm {\circ }}}$ ($L_{\mathrm{s}}$ is the areocentric longitude of the Sun). During this period, many interesting phenomena were observed: (1) Albedo features did not show a large difference from the first half of the period. (2) Blue clearings due to the opposition effect and due to the cloud effect were, respectively, observed. (3) South polar cap (SPC) recession was usual. The recession rate in $\sim 210 {{}^{\mathrm {\circ }}} \hbox{--} 270 {{}^{\mathrm {\circ }}}\mathrm{W}$ increased and that in $\sim 30 {{}^{\mathrm {\circ }}} \hbox{--} 60 {{}^{\mathrm {\circ }}}\mathrm{W}$ decreased after $L_\mathrm{s} \sim 230 {{}^{\mathrm {\circ }}}$. (4) North polar hood (NPH) had a topography-synchronous wave structure with $\mbox{a wave number} = 1$ a wave number$= 1$. (5) Many water ice clouds (WICs) were observed. Some particular regions frequently had prominent WICs. Some of them were related to topography. (6) Dust storm “2003c” was detected on December 9 ($L_\mathrm{s} = 314 {{}^{\mathrm {\circ }}}$) in Chryse. The storm grew rapidly to a very large dimension in the southern mid-latitudes, encircling over half of Mars. Another dust core occurred on December 23 around Aurorae Sinus. (7) Another dust storm is suspected in $L_\mathrm{s} = 20 {{}^{\mathrm {\circ }}}$ over the south polar region.