Mars in 2007 – Second interim report
A short note on the present apparition appeared in a previous Journal (118, 73–74 (2008)). Here we review some aspects of the observations from around opposition (2007 December 24) to 2008 late May, by which time the apparition was virtually over. We also report upon the safe landing of NASA’s Phoenix probe (Figure 1).
The weather in early 2008, at least in the UK and Europe generally, was not at all helpful. It was very frustrating to experience long runs of cloudy nights in the period just after opposition. The Director eventually managed to make over a hundred drawings: see Figure 3 for six examples. Paul Abel, Makoto Adachi, David Gray and Ian Hancock also made very detailed drawings. Gray enjoyed a particularly fine view in near-perfect seeing on December 11: see Figure 4. As in 2005 the majority of our observers have been taking digital images and video (Figures 2 and 5).
NASA’s Phoenix landed safely on May 25 (Ls = 76º) at lat. +68º, long. 234º, in Vastitas Borealis (midway between classical Utopia and Lemuria) making it the first such craft to land in either of the martian polar regions. At the time of landing, the bulk of the N. polar seasonal cap had already retreated well north of latitude +68º. (The average latitudes recorded by the BAA in the 1980s and 1990s at a mean Ls of 78º was +76º.) Phoenix has a stereoscopic camera and sample arm, each of which is presently working well. It also sports a meteorological station, a mass spectrometer for soil outgassing analyses, and facilities for microscopy and soil conductivity experiments. Its two primary aims are to assess the biological potential of the ice–soil interface, and to study the history of water in the martian arctic.
The spacecraft was starting to return many images, some of which are given in Figure 1, as this note was being written. A few days after landing, the probe examined the terrain between its footpads to discover that the upper soil (or regolith) had been dispersed by its descent thrusters upon landing to reveal a brighter, harder layer of what appears to be ice. The Phoenix website may be found at: http://www.nasa.gov/mission_pages/phoenix/main/index.html
Albedo charts and the aftermath of the global dust storm
In the previous report we listed the principal albedo feature changes resulting from the global storm. If we compare the regions from Margaritifer Sinus through Mare Erythraeum to Aurorae Sinus upon the comparative charts made by Jan Adelaar (Figure 2), we can see evidence of other changes in relative intensity. In particular, even by early 2008 the markings in general had still not returned to the intensities they had shown at opposition in 2005. Richard Baum found features still ‘somewhat subdued’ visually on January 10, and Alan Heath and the Director had similar impressions. Since our last report, the martian atmosphere has not shown any further signs of dust storm activity, at least none at the telescopic level of resolution.
According to our BAA Section reports of 1995, 1997 and 1999, the so-called Equatorial Cloud Band (ECB) is a more or less constant feature from northern mid-spring till late summer (Ls = 50–145º, approximately). The post-opposition observations in 2008 also show this feature from the anticipated time onwards. See Figures 3F and 5C. The seasonal presence of thin white cloud crossing the Syrtis Major produces the so-called Syrtis Blue Cloud: see Figure 5D. Long strips of white cloud have also been seen in the temperate latitudes of both hemispheres: these were beautifully shown on Hubble Space Telescope images taken in December, and can also be traced in Figure 5A.
Other white clouds have become prominent as the season progressed and the N. polar cap recessed, in particular the orographic clouds over Olympus Mons and the Tharsis volcanoes (Figure 5A) These latter clouds show a longer range in Ls than the ECB, but the volcanoes behave individually on account of their different latitudes.
In addition to those listed in the previous note, useful data were received from:
A full Report will be prepared later. Meanwhile, my thanks are due to all contributors for achieving such an excellent level of coverage over many months.
Figure 1 : Images of the martian northern plains from NASA’s Phoenix lander. (Courtesy NASA/JPL–Caltech/University of Arizona/Texas A&M University.)
|A 360-degree view of the horizon (north at top) compiled on Sols 1 and 3 at different local times.||Colour view to the north-west of the lander, showing terrain with a polygonal cracking pattern, sprinkled with small pebbles, extending away from the craft; Sol 2.|
A Sol 5 image showing the result of soil removal by Phoenix’s
descent thrusters (visible at the top of the picture).
A scale model montage of NASA’s Mars landers and rovers from Sojourner (1997) up to the forthcoming Mars Science Lab (scheduled to be launched in 2009).
Figure 2 : Comparative Mars apparition charts for 2005 and 2007, compiled by Jan Adelaar (Arnhem, Netherlands) from personal images (235-mm SCT; Philips ToUcam webcam, 2005 October 6–November 9; DMK camera, 2007 November 15–December 30). South at top. (See Maps.)
Figure 3 : Drawings by the Director (R. McKim), 410-mm Dall–Kirkham Cass., x256, x410. South at top.
A 2007 December 12d 21h 15m, CML =
285°. Hellas is very bright.
B 2007 December 13d 20h 35m, INT
(integrated light) + W23A (orange), CML
= 266°. Note the new albedo streak
C 2008 January 16d 22h 05m, W23A, CML = 348°. NPC seen. (In blue light, a larger, overlying N. polar hood was evident (Ls = 19°).)
D 2008 February 4d 18h 40m, INT, CML = 126°. Solis Lacus is extended to the NW; Mare Sirenum is extended NE
towards Phoenicus Lacus; Olympus Mons is visible.
E 2008 February 11d 18h 00m, INT + W23A, CML = 52°. Nilokeras–Ganges is well seen. Argyre is bright within the
S. polar hood.
F 2008 March 21d 19h 10m, CML = 63°. ECB (dashed lines) is seen to be running from the evening Chryse/Xanthe to
the morning Tharsis, at Ls = 48°. Whiteness also exists in Argyre and Tempe.
Figure 4 : Drawing made by D. Gray on 2007 December 11d 20h 50m, 415-mm Dall–Kirkham Cass., x365, Seeing I–II, CML = 287°. Fine details abound; the best view ever obtained by this observer.
Figure 5 : Selected images as Mars receded from Earth after opposition. Not to scale. South at top.
A 2008 January 9d 05h 12m, CML = 164°, 410-
mm refl., Skynyx 2-0, D.C. Parker. Bright
evening clouds over Arsia Mons, Ascraeus Mons
and Pavonis Mons, with fainter afternoon cloud
over Olympus Mons at Ls = 15°; note the
resolution of the remarkably fine details within the
southern maria. (D = 14.7”.)
B 2008 February 12d 21h 08m, CML = 88°, 356-
mm SCT, DBK 21AF04 AS colour camera,
A.S.Kidd. Fine details in Solis Lacus, which retains
its new shape since the global dust storm. The
calderae of all four volcanoes from A are shown
on the morning side as small dark spots. (D =
C 2008 May 8d 01h 00m, CML = 59°, 410-mm refl., Skynyx 2-0, D.C. Parker. RGB and blue (480 nm) images are
shown, the latter best showing equatorial cloud belt extending from a bright terminator cloud over Tharsis, to Chryse,
at Ls = 69°. Also note a white cloud streak over Tempe. (D = 5.5”.)
D 2008 May 14d 00h 04m, CML = 347°, 320-mm refl., DMK 21AU04.AS camera, S. Walker. Syrtis Major at the evening
limb looks bluish, being affected by evening cloud (forming part of the ECB) extending over it from Aeria. (D = 5.4”.)
Richard McKim, Director