Always an intriguing world, Mars offers both casual and serious observers many challenges and delights. It also provides astronomers a laboratory to study the atmosphere and surface of another planet, including the behavior of condensates and their effects on its atmosphere and surface. Mars is similar to Earth in that it has four seasons, exhibits global climates, changing weather patterns, annual thawing and growing of polar caps, storm clouds of water ice, howling dusty winds, and a variety of surface features that predictably change in color and size and appear to shift position over extended periods of time.

Mars appears more Earth-like to us than most of the other planets because we can observe its surface, atmospheric clouds and hazes, and its brilliant white polar caps. The latter are composed of frozen CO2 and underlying water ice, and wax and wane during the Martian year. These aspects, along with the changing seasons and the possibility of life, have made Mars one of the most studied planets in our solar system.

The Red Planet Mars offers both casual and serious observers many challenges and delights, as well as providing astronomers a laboratory to study another planet's atmosphere and surface. Some Martian features even appear to shift position around the surface over extended periods of time.

There are several cooperating international Mars observing programs under way to assist both professional and amateur astronomers. These include the International Mars Patrol (I.M.P.) coordinated by the Mars Section of the Association of Lunar and Planetary Observers (A.L.P.O), the International MarsWatch, the Terrestrial Planets Section of the British Astronomical Association (B.A.A.), and the Mars Section of the Oriental Astronomical Association (O.A.A.).

Information for observing Mars during a typical apparition is presented in a separate report titled, "General Information for Apparitions of Mars." This report can be found on the Internet at URL: http://www.tnni.net/~dustymars/General_Info_Mars.htm

With the advent of modern CCD camera technology the amateur can produce useful images of Mars when it is as small as 3.5 arcsec. Early in an apparition, Mars rises in the east or morning sky and sets with the rotation of the Earth in the western or evening sky. During the past few apparitions (2001-2005), observers began to take CCD images when Mars was only 32 degrees away from the Sun. Since Mars was only a visual magnitude of ~1.8 then the planet would have been difficult to locate bright twilight hours.

In the pre-apparition reports the observer will find the motion of Mars in our sky, the characteristics for that particular apparition, information pertaining to the polar cap(s) and any special events that may be seen during that particular apparition. As usual a calendar of events will be included with each report that contains cardinal dates for seasonal activity and orbital information of Mars.

As a general rule, an "apparition" begins when a planet emerges from the glare of the Sun shortly after conjunction. Mars will be in conjunction when the Sun on October 23, 2006 (124.5deg Ls); however, Mars will disappear behind the Sun around October 11, 2006 and will not emerge from the Sun until 24 days later on November 04.

The apparent declination of Mars begins at -23.2deg in mid-January 2007, and then begins to climb northward until crossing through the celestial equator on May 21, 2007 in the constellation Pisces. Mars continues to increase in declination and will reach 26.7deg on opposition day. This is good news for those observing in the Northern Hemispheres because Mars will be seen high in their sky. Mars will continue to be above the celestial equator to the remainder of the apparition crossing from the constellation Pisces into Aries during the end of June. By September 18, 2007, a '0' visual magnitude Mars is seen rising early in the morning sky in the constellation Taurus, it will be at western quadrature (90deg west of the Sun) and the phase or terminator will be at its widest (44deg).

In 2007 Mars begins retrogression, or retrograde motion against the background stars nearly thirteen months after conjunction November 16, 2007 (348deg Ls) through January 31, 2008 (25.2deg Ls). Each night for this brief period before, during and after opposition the Red Planet will appear to move backwards toward the western sky from the constellation Gemini into Taurus.

Since the Martian year is about 687 Earth days long -- nearly twice as long as ours, the Martian seasons are similarly extended. While the Earth's seasons are nearly equal in duration, the Martian seasons can vary by as much as 52 days from each other due to that planet's greater orbital eccentricity (see Figure 1)

Figure 1. A heliographic chart of the orbits of Mars and the Earth showing the relative seasons of both planets in the planetocentric longitude system Ls. Graphic Ephemeris for the 2007 Aphelic Apparition of Mars. Original graph prepared by C.F. Capen and modified by J.D. Beish.

Another general rule for predicting oppositions of Mars is from the following: the planet has an approximate 15.8-year periodic opposition cycle, which consists of three or four Aphelic oppositions and three consecutive Perihelic oppositions. Perihelic oppositions are also called "favorable" because the Earth and Mars come closest to each other on those occasions. We sometimes refer to this as the seven Martian synodic periods. This cycle is repeated every 79 years (+/- 4 to 5 days) and, if one were to live long enough, one would see this cycle nearly replicated in approximately 284 years. The 2007 Mars apparition is considered transitional because the orbital longitude at opposition will be only 63deg from the aphelion longitude 70deg Ls (Ls will be defined later).

Closest approach occurs at 0018 UT on December 19, 2007 (4.7deg Ls) with an apparent planetary disk diameter of 15.9'' at a distance of 0.589466803488 astronomical units (AU) or 54,794,253 miles (88,182,979 km). [NOTE: one (1) A.U. equals 92,955,621 miles or 149,597,870 km]. It should also be noted that closest approach between Earth and Mars is not necessarily coincident with the time of opposition but varies by as much as two weeks.

Opposition occurs fourteen months after conjunction, when Mars is on the opposite side of the Earth from the Sun. At that time, the two planets will lie nearly in a straight line with respect to the Sun, or five weeks after that retrogression begins. Opposition will occur at 1941 UT on December 24, 2007 (7.1deg Ls), with an apparent planetary disk diameter of 15.8 arcsec. Mars will remain visible for eleven months after opposition and then become lost in the glare of the Sun again (November 23, 2008) as it approaches the next conjunction (December 05, 2008). The cycle is complete in 780 Earth days.

Figure 2. A simulated view of the appearance of Mars during opposition at 1941 UT on December 24, 2007 (7.5deg Ls).

The observable disk diameter of Mars will be greater than 6 arcsec from June 14, 2007 [7.2deg d] (257.1deg Ls) and will not fall below this value until April 24, 2008 (62.8deg Ls), lasting 10 and a half months or 166 degrees Ls. During a similar profile in 2005 Mars began at 6 arcsec on April 07, 2005 [-19.6deg d] (188.7deg Ls) and continued March 24, 2006 (29.3deg Ls), equaling 11 and a half months or 200 degrees Ls. Imaging by CCD devices may begin with a disk diameter of 4 arcsec or less, commencing on January 10, 2007.

During closest approach in 2007 the apparent diameter of Mars will be more than 4 arcsec smaller than it was at the same period in 2005; however, it will be 10 degrees higher in the sky – much better for observing the Red Planet – helping to make up for the smaller size.

The Sub-Earth (De) and Sub-Solar (Ds) points are graphically represented in Figures 3 and 4. The 2007 and 2008 Ephemeris of Mars is tabulated the following URL: http://www.tnni.net/~dustymars/eph07_08.html A glossary of Terms appears at the end of this table.

Figure 5 graphically illustrates the ephemeris of Mars for 2007, showing the apparent diameter of the planet. Figure 6 illustrates the Martian apparitions for 2001, 2003, 2005 and 2007.

Figure 3. As it approaches Earth, it will swell from a small apparent disk of 6" in June 14, 2007 to a maximum diameter on December 18, 2007, and then shrink as it moves away. Closest approach occurs on December 19, 2007 (Opposition December 24, 2007). From June 2007 through April 2008 are the prime observing months.

Figure 4. Graphic Ephemeris of Mars during the 2007-2008 apparition from January 1, 2007 through December 31, 2008. Opposition and 6 arcsec apparent diameter range arc indicated. Plot illustrates the Declination (black line), the latitude of the Sub-Earth point (De) or the apparent tilt (brown line) in areocentric degrees, and the latitude of the Sub-Solar point (green line) in areocentric degrees. The areocentric longitude (Ls) of the Sun, shown along the bottom edge of the graph defines the Martian seasonal date. The value of Ls is 0deg at the vernal equinox of the northern hemisphere, 70deg when Mars is at aphelion, and 90deg at the summer solstice of the northern hemisphere 250deg when Mars is at perihelion, and 180deg is northern autumn.

Figure 5. Graphic Ephemeris of Mars from January 1, 2007 through December 31, 2008 Plot illustrates the apparent diameter of Mars in seconds of arc. The areocentric longitude (Ls) of the Sun, shown along the bottom edge of the graph defines the Martian seasonal date.

Figure 6. Graphic plot comparing the declination of Mars during the 2001, 2003, 2005 and 2007 apparitions. The Areocentric longitude (Ls) of the Sun, shown along the bottom edge of the graph, defines the Martian seasonal date. Oppositions years are shown at top of vertical lines. Opposition date 2001[177deg Ls] - (blue line), for 2003[249deg Ls] - (green line), 2005 [320deg Ls] - (orange line), and 2007 [7deg Ls] – (violet line).

Astronomers will have a view of both polar regions during the next apparition. On January 9, 2007 the Martian South Polar Region (SPR) began to tilt toward the Earth and will remain so until September 13th when it reaches 0deg De. Also, the terminator may begin to cover the cusp of the polar cap because the Ds will then begin to move southward, or more negative, along with the southward direction of the De. After that, the South Pole will be in the shadow of the southern portion of the limb terminator. By the first week week in March (195deg Ls), the SPC should be free of its hood, enough so to begin micrometer measurements. The north polar region will begin to tilt towards Earth in september and remain positive until the end of 2007. For more detailed information on the south polar cap go to and click: http://www.tnni.net/~dustymars/SPR.htm
or the north polar cap click:
http://www.tnni.net/~dustymars/NPR.htm

Observations of Mars indicate that major dust storms tend to be more frequent when Mars is closest to the Sun – during southern hemisphere spring and summer. While predicting these events is nearly impossible to make our studies show that the Martian dusty season should begin about the third week in May (241deg Ls) throughout the first week in July 2007 (270deg Ls). The highest probability of dust storms occurring will be on or about June 11, 2007 (255deg Ls) and a sensitive area for the development of dust storms is in northwest Hellas.

Massive, planet-encircling storms usually occur in southern hemisphere summer and that will come by the middle of September (315deg Ls). Observers should be alert for dust clouds in the northeast Hellas Basin, the Serpentis-Noachis region, and the Solis Lacus region. If the Red Planet behaves as it did in 2001 and 2003, then 2007 may be a time when Mars may be very dusty indeed! For more detailed information on Martian dust storms click to the URL: http://www.tnni.net/~dustymars/2003_DUST.htm

For those interested in catching a glimpse of possible "flashes" from the surface of Mars there will be two periods when possible "flashes" may be seen on Mars. When the De and Ds are coincident will be on or about December 20, 2007. See table below for dates when De = Ds +/- 1.0deg:

First Period: EST = UT - 4 || Di = 5.7" – 5.9"

Second Period: EST = UT - 5 || Di = 15.9"

                 NOTE: Di = apparent diameter of Mars
                                    De = Declination of Earth from Mars
                                    Ds = Declination of Sun from Mars
                            De - Ds = coincident
                                        i = phase defect in degrees