THE 2039-2040 APPARITION OF MARS
By: Jeffrey D. Beish (21-DEC-2020)

INTRODUCTION

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.

MOTION OF MARS IN OUR SKY

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.


2040 APPARITION CHARACTERISTICS

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.

Opposition occurs 14 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 retrogression begins. Opposition will occur at 1521UT on January 02, 2040 (16.3° Ls) with an apparent planetary disk diameter of 15.3 arcsec. Mars will remain visible for 10 months after opposition and then become lost in the glare of the Sun around November 05, 2040; as it approaches the next conjunction (December 17, 2040). The cycle is complete in 780 Earth days. By April 06, 2040 will be at eastern quadrature with the phase defect or terminator of 37.0°.

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.


THE NORTH AND SOUTH POLAR REGIONS

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.

DUST STORMS

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.


CALENDAR OF EVENTS -- MARS, 2039 - 2040

DATE

REMARKS

2038-Nov-01

Ls 133.3°

Conjunction. Mars is behind the Sun ~2.572AU.

2039-Jan-29

Ls 180.0°

Dia 4.1’

Equinox - Northern Autumn/Southern Spring . South Polar Cap (SPC) maximum diameter, subtending ~ 60.5° W. Is the North Polar Hood present. Does SPH or frost cover Hellas? Hellas should begin to clear and darken. Are W-clouds present? South cap emerges from darkness of Winter. SPH thinning and forms "Life Saver Effect."

2039-May-24

Ls 250.0°

Dia 5.4’’

Mars at Perihelion . SPC in rapid retreat. Novus Mons smaller. Dust clouds expected over Serpentis-Hellaspontus (Ls 250° - 270). Syrtis Major narrow. Frost in bright deserts? Orographic clouds (W-clouds) possible. Elysium and Arisa Mons bright? Note: Several "planet-encircling dust storms have been reported during this season. High probability 255° Ls. (SPC W ~24.4° ±2.6°).

2039-Jun-25

Ls 270°

Dia 5.8’’

Solstice - Northern Winter/Southern Summer. W-clouds present? NPH extends 50° N? Decreased number of White clouds. "Syrtis Blue Cloud"? White areas in deserts? Dust clouds in south until 270° Ls? Watch for planetary system clouds bands. Orographic cloud over Arsia Mons? Syrtis Major is narrow.

2039-Jul-02

Ls 274.4°

Dia 6’’

Apparition begins for visual observers using 4-inch to 8-inch apertures telescopes and up. Begin low-resolution CCD imaging. Views of surface details not well defined. W-clouds present? NPH extends 50° N? Decreased number of White clouds. "Syrtis Blue Cloud"? White areas in deserts? Dust clouds in south until 270° Ls? Watch for planetary system clouds bands. Orographic cloud over Arsia Mons? Syrtis Major is narrow.

2039-Sep-14

Ls 318.8°

Dia 8”

Wave or frontal cloud activity from NPR? Bright spots in Hellas? Orographic cloud over Arsia Mons? Topographic cloud over Libya? Topographic cloud over Edom?

2039-Sep-28

Ls 326.7°

Dia 8.6”

Mars at western quadrature Wave or frontal cloud activity from NPR? Bright spots in Hellas? Orographic cloud over Arsia Mons? Topographic cloud over Libya? Topographic cloud over Edom? High probability of dusty storm at 315° Ls.

2039-Oct-21

Ls 339.3°

Dia 10’’

NPC large hood present. W-Cloud? Orographic cloud over Arsia Mons? Topographic cloud over Libya? Topographic cloud over Edom?

2039-Nov-14

Ls 351.8°

Dia 12’’

NPC large hood (NPH) present. Discrete (white) clouds and white areas should be seen. Syrtis Major begins to expand to its east. Topographic cloud over Libya?

2039-Nov-23

Ls 356.4°

Dia 12.9’’

Retrogression Begins. NPC large hood (NPH) present. Discrete (white) clouds and white areas should be seen. Syrtis Major begins to expand to its east. Topographic cloud over Libya?

2039-Nov-302

Ls 0°

Dia 13.6”

Northern Spring/Southern Autumn Equinox. North Polar Hood (NPH) breaking up, North Polar Cap (NPC) should be exposed and near to 65° areographic latitude. SPC very small, difficult to see. White areas? Orographic clouds over the Tharsis volcanoes. W-Cloud?

2039-Dec-28

Ls 13.6°

Dia 15.3’’

Mars at Closest Approach. High-resolution CCD imaging and photography. North Polar Hood (NPH) breaking up and North Polar Cap (NPC) should be exposed. Hellas and Argyre bright?

2040-Jan-02

Ls 16.0°

Dia 15.3”

Mars at Opposition . NPC nearly static or entering erratic retreat, hood dissipating? Orographic cloud over Apollinaris Petera?

2040-Feb-08

Ls 33.2°

Dia 12”

Limb clouds and hazes should start to increase. Dust clouds in NPR?

2040-Feb-09

Ls 33.7°

Dia 11.9”

Retrogression Ends. Limb clouds and hazes should start to increase. Dust clouds in NPR? Few clouds. Limb arcs increasing in frequency or intensity? Arctic hazes and clouds? Dust clouds in NPR?

2040-Mar-22

Ls 52.5°

Dia 8”

Continue NPC measurements. Is North Cap fairly static or entering rapid retreat phase. South polar regions becoming difficult to observe. Any signs of South Polar Hood (SPH)?

2040-Apr-07

Ls 59.5°

Dia 7.1”

Mars at eastern quadrature. Micrometer measurements of NPC possible. Watch for "Aphelic Chill" in North Polar region (NPR) – (usually between 60° and 70° Ls) and possible halt in thawing of NPC. Views of surface details well defined. Rima Tenuis may appear (140° and 320° areographic meridians). Cloud activity in north increasing?

2040-Apr-30

Ls 70.0°

Dia 6.1’’

Mars at Aphelion. Is North Cap fairly static or entering rapid retreat phase. Watch for "Aphelic Chill" in NPR (usually between 60° and 70° Ls). Antarctic hazes, hood. South polar regions becoming difficult to observe. Any signs of SPH? Cloud activity increases. Are limb arcs increasing in frequency, intensity?

2040-Dec-17

Ls 180.4°

Conjunction. Mars is behind the Sun ~ 2.450AU.