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) and the Terrestrial Planets Section of the British Astronomical Association (B.A.A.). Information for observing Mars during a typical apparition is presented in a separate report titled, “General Information for Apparitions of Mars.”  Also, you can find gobs of information at this site.

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 (2033-2037), 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 with the Sun on November 01, 2038 (1945UT); however, it will not be safe to observe Mars until after December 10, 2038 when it is at least 12 degrees away from the glare of the Sun.

The apparent declination of Mars begins at 13.5° in early July 2039 in the constellation Aries and will ascend north entering the constellation Taurus on July 21 and by September 28, 2039 will be at western quadrature with the phase defect or terminator of 42.8°. Mars continue northward until October 03 when it will begin to descend southward into Gemini. At this time Mars begins retrogression, or retrograde motion against the background stars eleven months after conjunction on November 23, 2039 (356.4° Ls) and continues through February 09, 2040 (33.7° Ls). Mars will then enter the constellation Cancer on April 27, 2040. This is good news for those observing in the Northern Hemispheres because Mars will be seen high in their sky.

By July 02, 2039, an '0.8' visual magnitude Mars will be seen rising early in the morning sky in the constellation Aries and by September 28, 2039 will be at western quadrature with the phase defect or terminator of 42.8°. NOTE: The Solar Elongation for Mars is the angle between the lines of sight from Earth to the Sun and from Earth to Mars. When these lines of sight form a right triangle then Mars is at quadrature (eastern or western). For detailed definitions and graphics for the motion of Mars in our sky see these excellent web sites: Planetary Aspects and Elongations and Configurations.

Figure 1. A heliographic chart of the orbits of Mars and the Earth showing the relative positions of both planets.  Quadrature is when Mars is directly east or west of Earth as shown.

The 2039-2040 apparition of Mars begins retrogression, or retrograde motion against the background stars eleven months after conjunction on November 23, 2039 (356.4° Ls) and continues through February 09, 2040 (33.7° Ls). Each night for this brief period of time; before, during and after opposition the Red Planet will appear to move backwards toward the western sky in the Gemini. 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 2).

Figure 2. 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 2039-2040 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 2040 Mars apparition is considered Aphelic because the orbital longitude at opposition will be 54° from the aphelion longitude of 70° Ls and 126° Ls from perihelion (250° Ls).

NOTE: Ls is the planetocentric longitude of the Sun along the ecliptic of Mars’ sky. 0° Ls is defined as that point where the Sun crosses the Martian celestial equator from south to north, that is the planet’s northern hemisphere vernal equinox. The other Ls values that define the beginnings of Martian northern hemisphere seasons are: summer, 90° Ls; autumn, 180° Ls; and winter, 270° Ls. For Mars’ southern hemisphere these values represent the opposite seasons. Distance (A.U.) - Distance from Earth to Mars in astronomical units, where one (1) A.U. equals 92,955,807.267 miles or 149,597,870.691 km.

Closest approach ooccurs at 1447UT on December 28, 2040 (13.6° Ls) with an apparent planetary disk diameter of 15.3'' at a distance of 0.6109153 astronomical units (AU) or 56,788,127 mi (91,391,631-km). During closest approach in 2040 the apparent diameter of Mars will be 3.7 arcsec smaller than it was at the same period in 2037; the declination will be virtually the same only 5.8 degrees higher in the sky - good for observing the Red Planet for observers in the northern and southern hemispheres of Earth. 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.

Figure 3. Figure 3. A simulated view of the appearance of Mars during opposition at 1521 UT on January 02, 2040 (16.3° Ls, CM 108.5°)

The observable disk diameter of Mars will be greater than 6 arcsec from July 02, 2039 [13.5° δ] (274.4° Ls) and will not fall below this value until May 03, 2040 [21.9° δ ] (70.9° Ls), lasting 10 months or 157 degrees Ls. Imaging by CCD devices may begin with a disk diameter of 4.5 arcsec or more, commencing on or about January 20, 2039.

The Sub-Earth (De) and Sub-Solar (Ds) points are graphically represented in Figures 4 and 5. The 2039-2040 Ephemeris of Mars is tabulated on Internet in this web site. A glossary of Terms appears at the end of this table.

Figure 4. As it approaches Earth, it will swell from a small apparent disk of 6" in July 02, 2039 to a maximum diameter of 15.3" at closest approach on December 28, 2039, and then shrink as it moves away. Images shown at 0h UT.

Figure 5. Graphic Ephemeris of Mars during the2039-2040 apparition from July 02, 2039 through May 03, 2040. Opposition January 02, 2040 (16.3° Ls) and 6 arcsec apparent diameter range are indicated. Plot illustrates the Declination (solid line), the latitude of the Sub-Earth point (De) or the apparent tilt (dashed line) in areocentric degrees, and the latitude of the Sub-Solar point (dotted 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 0° at the vernal equinox of the northern hemisphere, 71° when Mars is at aphelion, and 90° at the summer solstice of the northern hemisphere 251° when Mars is at perihelion, and 180° is northern autumn.

Figure 6. Graphic Ephemeris of Mars from July 02, 2039 through May 03, 2040. Opposition January 02, 2040 (16.3° Ls) and 6 arcsec apparent diameter range are indicated. 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.

Astronomers will have a view of both polar regions during this apparition. From the first week in July 2039 the Martian North Polar Region (NPR) will be positioned to be seen from the Earth and will remain so until mid-August, 2039. During the second week of August 2039 the South Polar Region (SPR) positioned to be seen from the Earth and remain in view for the remainder of this apparition. For more detailed information on both polar regions click the north polar cap and south polar cap.

Observers should be aware that massive, planet-encircling storms usually occur in the southern hemisphere summer and may occur to block our view of large areas in the south of Acidalium Mare, Chryse, Erythraeum Mare, Ophir and northeast Solis Lacus. While these events are nearly impossible to predict our studies show that the Martian dusty season should be ongoing from the beginning of the apparition through the end with the highest probability around June 01, 2039 (225° Ls) and again peaking on or about September 08, 2039 (315° Ls) often starting in northwest Hellas. When a great dust storm reaches maturity, Mars' disk appears bright orange and Mars' surface features are obscured. For more detailed information on Martian dust storms on this web site.

During the 2001 Apparition of Mars a group of amateur and professional astronomers gathered in a driveway on Cudjoe Key, about 20 miles northeast of Key West, Florida to witness an interesting phenomenon of flashes or flares within a large, flat crater Schiaparelli, classically called "Edom Promontorium," that was first reported by Japanese astronomer Saheki on July 01,1954 at1315UT. This phenomenon again was reported by McClelland in 1954 and Tasaka in 1958. The impetuous for the June 05 - 10, 2001 "planet observing party" came from two articles, "The Martian-Flares Mystery," Sky and Telescope, Vol. 101, No. 5, May, pp115-123, by Thomas A. Dobbins and William Sheehan, and "Solving the Martian Flares Mystery," Dobbins and Sheehan, ALPO Web Site. Dobbins had organized this event to record and to photograph Mars hoping the Edom flare would occur.

In a subsequent article Dobbins wrote in Sky & Telescope on March 4, 2004, that the observations supported the idea that, "The flares came from sunlight glinting off patches of frost or ice on the Martian surface." He states that "because the flashes occurred before Edom crossed the center of the planet's disk, the reflectors must have been tilted as much as 19° east-west; perhaps they rested on inclined surfaces on the ground, for example, the slopes of dunes. Intriguingly, the light-colored oval of Edom Promontorium corresponds to the large, flat crater Schiaparelli, and in May 2002 NASA's Mars Odyssey spacecraft found indications that this region is anomalously rich in water ice for a site near the Martian equator."

For those interested in catching a glimpse of possible "flares" from the surface of Mars there will be a period when it will be possible to see it as the De and Ds are coincident that will be on or about December 28, 2039. It is expected that Mars will be situated favorably in the sky for observers to record this rare event when the De and Ds will be very close together. When planning for the upcoming December 2039 event and based on the previous observations, the earliest one may expect to see the Edom flare would be around two hours before the time when Edom Promontorium would appear on the central meridian, see Table-1 below for dates when De - Ds +/- 1.0°: