Note: Archive copy. Original site was: http://www.tnni.net/~dustymars/2010_MARS.htm

THE 2010 APHELIC APPARITION OF MARS
By: Jeffrey D. Beish

ABSTRACT

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.


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), 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 (2001-2007), 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 when the Sun on December 05, 2008 (168.5° Ls); however, Mars will disappear behind the Sun around November 21, 2008 and will not emerge from the Sun until 28 days later on December 18.

The apparent declination of Mars begins at 18.8° in mid-January 2010 and continues to climb northward until opposition. This is good news for those observing in the Northern Hemispheres because Mars will be seen high in their sky. Mars will be above the celestial equator until August 1, 2010.  By October 29, 2009, a 0.5 visual magnitude Mars is seen rising early in the morning sky in the constellation Cancer, it will be at western quadrature (90° west of the Sun) and the phase or terminator will be at its widest (40°).

In 2010 Mars begins retrogression, or retrograde motion against the background stars just over a year after from December 22, 2009 (18° Ls) through March 11, 2010 (62° Ls). Each night for this brief period before, during and after opposition the Red Planet will appear to move backwards toward the western sky sky from the constellation Leo into Cancer.

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 2010 Aphelic Apparition of Mars. Original graph prepared by C.F. Capen and modified by J.D. Beish.


2010 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 2010 Mars apparition is considered transitional because the orbital longitude at opposition will be only 26° from the aphelion longitude 70° Ls (Ls will be defined later).

Closest approach occurs at 1844 UT on January 27, 2010 (43.8° Ls) with an apparent planetary disk diameter of 14.11'' at a distance of 0.663989469429 astronomical units (AU) or 61,721, 554 miles (99,331,411 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 nearly 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 about five weeks after that retrogression begins. Opposition will occur at 1948 UT on January 29, 2010 (44.3° Ls), with an apparent planetary disk diameter of 14.1 arcsec. Mars will remain visible for nearly a year after opposition and then become lost in the glare of the Sun again (January 21, 2011) as it approaches the next conjunction (February 6, 2011). The cycle is complete in 780 Earth days.
 
 

Figure 2. A simulated view of the appearance of Mars during opposition at 1948 UT on January 29, 2010 (44.3° Ls).


The observable disk diameter of Mars will be greater than 6 arcsec from September 8, 2009 [23.5° d ] (334.8 ° Ls) and will not fall below this value until June 01, 2010 [13.9 ° d ] (98.4° Ls), lasting nearly 9 months or 124 degrees Ls. During a similar profile in 2007 Mars began at 6 arcsec on June 14, 2007 [7.2° d] (257.1° Ls) and continued to April 24, 2008 (62.8° Ls), equaling equaling 10 and a half months or 166 degrees Ls.  Imaging by CCD devices may begin with a disk diameter of 4 arcsec or less, commencing on February 04, 2009.

During closest approach in 2010 the apparent diameter of Mars will be more nearly 2 arcsec smaller than it was at the same period in 2007 and it will be nearly 5 degrees lower in the sky – not great for observing the Red Planet.

The Sub-Earth (De) and Sub-Solar (Ds) points are graphically represented in Figures 3 and 4. The 2009 and 2010 Ephemeris of Mars is tabulated the following URL: http://www.tnni.net/~dustymars/eph09_10.html A glossary of Terms appears at the end of this table.

Figure 3. As it approaches Earth, it will swell from a small apparent disk of 6" in September 08, 2009 to a maximum diameter on January 28, 2010, and then shrink as it moves away.  Closest approach occurs on January 17, 2007 (Opposition January 29, 2010).  From September 2009 through June 2010 are the prime observing months.
Figure 4. Graphic Ephemeris of Mars during the 2009-2010 apparition from October 27, 2009 through July 19, 2010.   Opposition and 6 arcsec apparent diameter range arc indicated. Plot illustrates the Declination (blue line),   the latitude of the Sub-Earth point (De) or the apparent tilt (green line) in areocentric degrees, and the latitude of the Sub-Solar point (red 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, 70° when Mars is at aphelion, and 90° at the summer solstice of the northern hemisphere 250° when Mars is at perihelion, and 180° is northern autumn.
Figure 5. Graphic Ephemeris of Mars from October 27, 2009 through July 19, 2010.  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 Martian North Polar Region

Astronomers will have an excellent view of the prominent north polar cap during most of the next apparition because it will be tilted earthward during the last half of 2009 and throughout 2010.  On August 15, 2009 the Martian North Polar Region (NPR) will begin to tilt towards the Earth and will remain so for the remainder of the apparition.  However, the opposite side of the northern part of polar cap will in the terminator shadow until October 27, 2009 when the cap will be sunlit, except where covered by the eastern terminator that will be present.

For those interested in catching a glimpse of possible “flashes” from the surface of Mars the first occasion when the De and Ds are coincident at -24.2°, will be on or about May 03, 2009; however, Mars will only be 4.5 arcsec in apparent diameter then.  A better time to see possible flashes would be either on or about January 20, 2010 when the De and Ds will be at 15.8° and again on or about June 17, 2010 when the De and Ds are coincident at 23.8°.

For more detailed information on the north polar cap click to the URL: http://www.tnni.net/~dustymars/NPR.htm

SPECIAL EVENTS

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. The first occasion when the De and Ds are coincident will be on or about January 20, 2010 and again be on or about June 17, 2010. See tables below for dates when De = Ds +/- 1.0 degree:

First Period: EST = UT - 5 || Di = 13.84" through 14.08"
 

Date
Rise
Transit (EDT)
De
°
Ds
°
De - Ds
°
i
°
January 17
0006
0656 (0156)
16.2
15.3
0.9
10.9
January 18
0000
0651 (0151)
16.1
15.4
0.7
10.2
January 19
2355
0645 (0145)
16.0
15.6
0.4
9.4
January 20
2349
0640 (0140)
15.8
15.7
0.1
8.6
January 21
2343
0635 (0135)
15.7
15.9
-0.2
7.8
January 22
2338
0629 (0129)
15.6
16.0
-0.4
7.1
January 23
2332
0624 (0124)
15.5
16.2
-0.7
6.3
January 24
2326
0618 (0118)
15.3
16.3
-1.0
5.6

Second Period: EDT = UT - 4 || Di = 5.77" through 5.40"
 

Date
Rise
Transit (EST)
De
°
Ds
°
De - Ds
°
i
°
June 11
1559
2226 (1826)
23.2
24.1
-0.9
36.1
June 12
1558
2224 (1824)
23.3
24.1
-0.8
36.0
June 13
1556
2222 (1822)
23.4
24.0
-0.6
35.9
June 14
1555
2220 (1820)
23.5
24.0
-0.5
35.8
June 15
1553
2218 (1818)
23.6
23.9
-0.3
35.7
June 16
1552
2216 (1816)
23.7
23.9
-0.2
35.6
June 17
1550
2214 (1814)
23.8
23.8
0.0
35.5
June 18
1549
2212 (1812)
23.9
23.8
0.1
35.5
June 19
1548
2210 (1810)
24.0
23.7
0.3
35.4
June 20
1546
2209 (1809)
24.1
23.6
0.5
35.3
June 21
1545
2207 (1807)
24.2
23.6
0.6
35.2
June 22
1543
2205 (1805)
24.3
23.5
0.8
35.1
June 23
1542
2203 (1803)
24.4
23.4
1.0
35.0

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
 
 

Table 2. CALENDAR OF EVENTS -- MARS, 2010

DATE PHYSICAL REMARKS
2008 Nov 21 Ls 161° Conjunction Ingress. Mars will disappear behind the limb of the Sun.
2008 Dec 05 Ls 168.5° Conjunction. Mars is behind the Sun ~2.478 AU. 
2008 Dec 18 Ls 175.7° Conjunction Egress. Mars will emerge from behind the limb of the Sun.
2009 Apr 20 Ls 250.2°
De -25.0°
Ds -23.2°
RA 23:54
Dec -01.8°
A.Dia 4.4’’
Mars at Perihelion. Late southern spring. 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?  Frost in bright deserts? Novus Mons smaller. Note: Several "planet-encircling dust storms have been reported during this season. High probability 255° Ls.
(SPC W ~ 25.0° ±2.6°). 
2009 Sep 08 Ls 334.8°
De 6.5°
Ds -10.3°
RA 06:36
Dec 23.5°
A.Dia 6’’
Apparition begins for observers using 4-inch to 8-inch apertures telescopes and up. Begin low-resolution CCD imaging. Views of surface details not well defined. Novus Mons reduced to a few bright patches and soon disappears. Windy season on Mars begins, dust clouds present? Watch for initial dust clouds in south. White patches in bright areas? Hellas bright spots? Numerous bright patches   (SPC W ~9.4° ±0.5°).
2009 Oct 27 Ls 0°
De 16.0°
Ds 0.1°
RA 08:30
Dec 20.4°
A.Dia 7.7’’
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."   
2009 Nov 03 Ls 3.7° 
De 16.8° 
Ds 1.5° 
RA 08:43
Dec 19.8°
Audi 8’’
North Polar Hood (NPH) breaking up, North Polar Cap (NPC) should be exposed Hellas and Argyre bright?    (NPC W ~65°).
2009 Dec 02 Ls 17.7°
De 18.8°
Ds 7.3°
RA 09:23
Dec 18.0°
A.Dia 10’’
NPC nearly static and begin erratic retreat, hood continues to dissipate. Orographic cloud over Apollinaris Petera? (NPC W ~65°).
2009 Dec 22 Ls 27.0°
De 18.5°
Ds 11.0°
RA 09:32
Dec 18.1°
A.Dia 11.8’’
Retrogression Begins. Mars begins retrogression, or retrograde motion against the background stars nearly 3xx days after conjunction, when it appears to move backwards toward the west for a brief period before, during and after opposition.

 

2009 Dec 25 Ls 28.4°
De 18.4°
Ds 11.5°
RA 09:32
Dec 18.2°
A.Dia 12’’
Limb clouds and hazes should start to increase.  (NPC W ~65°).
2010 Jan 28 Ls 43.8°
De 14.8°
Ds 16.9°
RA 08:57
Dec 21.9°
A.Dia 14.1’’
Mars at Closest Approach.High-resolution CCD imaging and photography. Few clouds. Limb arcs increasing in frequency or intensity. Arctic hazes and clouds present?  (NPC W ~65°).
2010 Jan 29 Ls 44.3°
De 14.7°
Ds 17.0°
RA 08:55
Dec 22.1°
A.Dia 14.1’’
Mars at Opposition. Is NPC fairly static or entering rapid retreat phase. South polar regions becoming difficult to observe. Any signs of South Polar Hood (SPH)?  (NPC W ~46.0° ±1.4°)
2010 Mar 02 Ls 58.4°
De 12.1°
Ds 20.9°
RA 08:15
Dec 23.8°
A.Dia 12’
Watch for "Aphelic Chill" in 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?    (NPC W ~44.5° ±1.0°).
2010 Mar 11 Ls 62.4°
De 12.2°
Ds 21.8°
RA 08:13
Dec 23.6°
A.Dia 11.1’’
Retrogression Ends. Mars begins westward motion against the background stars. 

 

2010 Mar 23 Ls 67.6°
De 12.9°
Ds 22.8°
RA 08:16
Dec 23.0°
A.Dia 10’’
Is NPC fairly static or entering rapid retreat phase. Watch for "Aphelic Chill" in NPR (usually between 60° and 70° Ls). NPC Rima Tenuis may appear. Antarctic hazes, hood. South polar regions becoming difficult to observe. Any signs of SPH? Cloud activity increases. Are limb arcs increasing in frequency, intensity? (NPC W ~37.2° ±12.2°).
2010 Mar 29 Ls 70°
De 13.5°
Ds 23.2°
RA 08:20
Dec 22.6°
A.Dia 9.5’’
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? (NPC W ~37.4° ±0.8°).
2010 Apr 18 Ls 79°
De 15.9°
Ds 24.3°
RA 08:42
Dec 20.7°
A.Dia 8’’
NPC in rapid retreat? Are limb arcs increasing in frequency, intensity. Antarctic hazes/hood. Cloud activity increases. "Aphelic Chill" in NPR should be ended.  (NPC W ~30.0° ±1.3°).
2010 May 13 Ls 90°
De 19.5°
Ds 24.8°
RA 09:22
Dec 17.2°
A.Dia 6.7’’
Solstice - Northern Summer/Southern Winter. Orographic clouds over the Tharsis volcanoes – W-Cloud? Local seasonal clouds should wrap around Syrtis Major and be prominent in Lybia. Hellas white cloud and Ice-fog activity? Discrete clouds? NPC remnant? Lemuria (210° W, 82° N) detached from NPC? Any other detachments (projections at 135° W and 290° W) near NPC remnant? 
(NPC W ~22.3° ±1.1°).
2010 Jun 01 Ls 98.4°
De 22.1°
Ds 24.5°
RA 09:58
Dec 13.9°
A.Dia 6’’
Is North Cap fairly static or entering rapid retreat phase. South polar regions becoming difficult to observe. Any signs of SPH? Discrete clouds? Increasing ice-fogs and clouds? (NPC W ~19.3° ±0.4°).
2010 Nov 13 Ls 180° Equinox - Northern Autumn/Southern Spring
2011 Jan 21 Ls 221° Conjunction Ingress. Mars will disappear behind the limb of the Sun.
2011 Feb 06 Ls 231° Conjunction. Mars is behind the Sun ~2.374AU.