2001 PERIHELIC APPARITION OF MARS

Jeff Beish, ALPO Mars Section

INTRODUCTION

In addition to Mars appearing more Earth-like to observers than other planets because we see both its surface and atmospheric features, it displays white polar caps. These brilliant white caps of Mars, composed of CO2 and underlying water-ice (in the north at least), wax and wane during the Martian year. This along with the changing season's and the possibility of life has made Mars one of the most study planet in our solar system.

Now more than ever an intriguing world, Mars offers the casual and serious observer alike many challenges and delights. This planet offers astronomers a free laboratory for the study of another planet's atmosphere: the behavior of condensates and effects on its atmosphere. Mars is similar to Earth in that it has four seasons, exhibits global climates, changing weather patterns, annual thawing of polar caps, storm clouds of water ice, howling dusty winds and a variety of surface features which predictably change with color and size and appears to shift around the surface over long periods of time.

Amateur planetary astronomers contribute greatly to man's knowledge about current weather and surface conditions on the planet Mars. Armed with a quality telescope of 6 or greater inches in aperture and a set of color filters the amateur can produce professional quality telescopic work in planetary research. Furthermore, a well-equipped observer using CCD technology has the opportunity to produce professional quality observations.

Several cooperating international Mars observing programs have been under way and will continue to assist both the professional and amateur alike; 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 2001, the Terrestrial Planets Section of the British Astronomical Association (B.A.A.), and Mars Section of the Oriental Astronomical Association (O.A.A.).

2001 APPARITION CHARACTERISTICS

The 2001 Mars apparition is considered Perihelic because the orbital longitude at opposition is only 73° from the perihelion longitude (250° L_S). Opposition occurs on June 13, 2001, with an apparent planetary disk diameter of 20.4"; and a maximum diameter of 20.8" occurs eight days later on June 21. Mars has an observable disk diameter greater than 6 seconds of arc during the entire year. A useful disk diameter of 10 seconds of arc for film-photography exists for a period of 6 months, from March through October. Imaging by CCD devices may begin with a disk diameter of 8 seconds of arc or less, commencing on March 5th. The geometry of the heliocentric aspects of Mars relative to the Earth is shown in Figure 1.

In June of 2001 Mars will approach the Earth closer than at any time since the Perihelic apparition of 1988. For nearly three months, from May 14th until August 8th, the Red Planet's apparent size will be larger than it has been in over these past 13 years. Mars will be at a distance of 0.45016 A.U. or 41,844,902 miles (67,342,977 km) from Earth at Closest Approach. [NOTE: one (1) A.U. Equals 92,955,621 miles or 149,597,870 km].

Although Mars has a favorable apparent disk diameter for observing, it will be relatively low on the horizon during the entire apparition for observers in the middle northern latitudes, which will make the quality of astronomical seeing below average. The apparent declination of Mars from -12° to -17° throughout January, 2001; Mars then continues southward until it reaches -26° in mid-June (opposition time) until the first week in August when it settles to -27°; and then it slowly rises to -7° by the end of December 2001. The maximum altitude of Mars when on the terrestrial meridian will be approximately 22° to 35° for an observer in the United States. Consequently, observers located in the Southern Hemisphere will have the planetary disk high in the sky, where observing conditions can be ideal.

The aspects and range of the axial tilt of the globe of Mars make it possible to observe both poles and equatorial region during the 2001 apparition. The global tilt is synonymous to the apparent declination of the Earth (De) as viewed areocentrically ("Areo-" is a prefix often employed when referring to Mars or "Ares."), which is also the sub-earth point or latitude of the center of the Martian disk.

The De is tabulated in the Mars Section of the A.L.P.O.'s Internet Web Page (http://www.lpl.arizona.edu/~rhill/alpo/mars.html) and published in the A.L.P.O. Mars Section newsletter, the Martian Chronicle. Look under the heading, "Ephemeris for Physical Observations - 2001," in the "Mars Observing Ephemeris for 2001." The sub-earth and sub-solar points are graphically represented in Figure 2.

DAYS AND SEASONS ON MARS

The Martian solar day, also called a "sol" by space scientists, is about 40 minutes longer than a day on Earth. Thus Mars rotates through only 350° of longitude in 24 hours. An astronomer on Earth, who observes a particular surface feature on Mars, on a particular night, sees the same feature 10° further to its west (closer to its morning limb) the next night at the same civil time.

Mars and Earth have four comparable seasons because their axes of rotation are each tilted at about the same angle to their respective orbital planes. In describing Martian seasons, scientist use the term "L_S" which stands for the Areocentric longitude of the Sun along Mars' ecliptic. ("Areo-" is a prefix often employed when referring to Mars or "Ares.") Mars' axial tilt is 25.2° as compared to 23.5° for that of the Earth. The Martian year is 687 Earth days, nearly twice as long as ours, so that the Martian seasons are similarly longer. While Earth's are nearly equal in duration, the length of a Martian season can vary by as much as 52 days because of the greater eccentricity of its orbit.

The axis of Mars does not aim at our North Star, but is displaced about 40° towards Alpha Cygni. Because of this celestial displacement the Martian seasons are 85° out of phase with the terrestrial seasons, or about one season in advance of ours. Consequently, when you observe Mars next spring and summer you will be seeing summer and autumn, respectively, in the Martian Southern Hemisphere.

MAKING OBSERVATIONS OF MARS

Data records of each visual and photographic observations (including CCD imaging) are very important. A complete written record should be made in some chosen order each night, and never left to memory for the following day. The Universal Date and Time, telescope used, ocular power (magnification) or Barlow lens, "astronomical seeing," sky transparency, filters employed, and a description of the observed Martian disk appearance in different color filters are recommended data whether or not they accompany a visual drawing.

However, the ancient art of visual observation at the telescope is still a most useful tool to the modern astronomer, and is the forte of the amateur astronomer. This year we are fortunate in that Mars will be very favorably positioned for telescopic study. This is especially important in view of the space missions to Mars currently under way and planned missions for the next century.

Even at its best, though Mars can be challenging to observe. The disk is diminutives and its markings are blurred by the Earth's atmosphere. A telescope for planetary work should provide sharp images with the highest possible contrast. A long-focus refractor is generally considered the best, followed by a long-focus Newtonian or Cassegrain reflector. Telescopes with large central obstructions do less well.

Anyone who observers Mars will find it rewarding to make a sketch of whatever is seen, both to create a permanent record and to help train the eye in detecting elusive detail. Start with a circle 1-3/4 inches (42 mm) in diameter. Draw the phase defect, if any, and the bright polar caps or cloud hoods. Next shade in the largest dark markings, being careful to place them as exactly the locations on the disk as possible. At this stage, record the time to the nearest minute. Now add the finer details, viewing through various color filters, starting at the planet's sunset limb. Finally, note the date, observer's name, the instrument(s) used, and any other relevant information.

Today's modern technology, such as a CCD camera, has increased the efficiency of telescopes that in the past were considered less than desirable for visual observations. Employing computer image processing many of the undesirable elements, such as low contrast and field illumination, can be reduced using image-processing programming. Because the CCD devices can capture an image much faster than by conventional means, on film, atmospheric turbulence is less likely to spoil the images -- another plus.

It is highly recommended that all observers, visual as well as photographers and CCD camera users, use at least a basic set of tricolor filters according to the following guide: Red or Orange (W-25 or W-23A); Green (W58); Blue-Green (W-64); Blue (W-38A or W-80A); and Violet (W-47). Observers with smaller telescopes, such as 3 to 6-inch apertures may find a Yellow (W-15) useful and may provide better performance than the deep red filter (See Table 1). Those employing larger instruments, such as 8 to 16-inch apertures, will find the deep Red and Blue filters most useful for fine surface details or atmospheric cloud detection [Capen, et al, 1984].

The Martian Central Meridian (CM) is an imaginary line passing through the planetary poles of rotation and bisecting the planetary disk and is used to define what areographic longitudes are present on the disk during an observing session. It is independent of any phase which may be present — if Mars presents a gibbous phase the CM will appear to be off center. The CM value is the areographic longitude in degrees which is on the central meridian of the disk as seen from Earth at a given Universal Time (U.T.). It can be calculated by adding 0.24°/min., or 14.6°/hr., to the daily CM value for 0h U.T. as listed in The Astronomical Almanac.

The terminator (phase defect) is the line where daylight ends and night begins. The terminator phase, or defect of illumination, is given in seconds of subtended arc on the apparent disk, or in degrees (i) or the ratio (k), to define how much of the geometrical Martian disk is in darkness. The sunset terminator appears on the east side, or evening limb, before opposition; and after opposition, the terminator becomes the sunrise line on the morning limb on the west side. At opposition there is no perceptible phase defect.

The axial tilt. The declination of the planet Earth (De) as seen from Mars defines the axial tilt of Mars relative to Earth. The De is also equal to the areographic latitude of the center of the Martian disk, which is known as the subearth point. The latitude is (+) if the north pole is tilted toward Earth and (-) if the south pole is tilted toward Earth. This quantity is an important factor when drawing Mars or when trying to identify certain features.

SURFACE FEATURES OF MARS

The dark surface markings were once thought by some astronomers to be great lakes, oceans, or vegetation, but space probes in the 1970's revealed the markings to be vast expanses of rock and dust. Windstorms sometimes move the dust, resulting in both seasonal and long-term changes.

Among the areas where yearly variations have been recorded are Trivium-Elysium, Solis Lacus, Syrtis Major, and Sabaeus- Meridiani. The Syrtis Major is the planet's most prominent dark area. Classical observations have revealed seasonal variations in the breadth of this feature: maximum width occurring in northern mid summer (145° L_S), and minimum during early northern winter, just after perihelion (290° L_S) [Antoniadi, 1930, Capen, 1976]. However, recent observations by ALPO astronomers and by the Hubble Space Telescope (HST) suggest that no such variations have occurred since 1990 [Lee, et al., 1995. Troiani, et al., 1988].

Solis Lacus, the "Eye of Mars", is notorious for undergoing major changes. In 1977 amateur observers discovered a new dark feature in the Aetheria desert at longitude 240° west, 25° north, between Nubis Lacus and Elysium. It was subsequently found on Viking Orbiter photographs taken in 1975, apparently undetected by Viking scientists at the time. This is an example of the importance of ground-based observations of the Solar System.

Another feature that is of great interest to professional Mars researchers is the Trivium-Cerberus, on the southern rim of the Elysium shield. A classically dark feature 1300×400 km in size, it has all but disappeared during the 1990's [Moersch et al., 1998. Troiani et al., 1998].

MARTIAN METEOROLOGY

Clouds and Hazes - The Martian atmosphere is ever-changing. White water ice clouds, yellowish dust clouds, bluish limb hazes, and bright surface frosts have been studied with increasing interest in the past two decades. Clouds seem to be related to the seasonal sublimation and condensation of polar-cap material. An intensive study of Martian meteorology has been conducted by the ALPO Mars Section using visual data and photographs from professionals and amateurs around the world. The first report, published in 1990, analyzed 9,650 IMP observations submitted over eight Martian apparitions between 1969 and 1984 [Beish and Parker, 1990]. This study has now been expanded to include 24,130 observations between 1965 and 1993. Statistical analysis indicates that discrete water ice crystal cloud activity and surface fog occurrence is significantly higher in the spring and summer of the Martian Northern Hemisphere than the same seasons for the Southern Hemisphere.

For inclusion in this unique study, it is essential that ALPO astronomers employ blue filters when making visual, photographic, or CCD observations.

Discrete clouds - have been observed on Mars for over a century. In 1954, a remarkable W-cloud formation was found to be recurring each late-spring afternoon in the Tharsis-Amazonis region. A decade later, C.F. Capen proposed that the W-clouds are orographic (mountain-generated), caused by wind passing over high peaks. Indeed, in 1971 the Mariner 9 spacecraft probe showed them to be water clouds near the large volcanoes Olympus Mons (longitude 133° west, latitude 18° north), Ascraeus Mons (104° W, 11° N), Pavonis Mons (112° W, 0° N), and Arsia Mons (120° W, 9° S). The W-clouds should be active during the 1999 apparition at least until opposition (129° L_S) and, perhaps, late in the apparition, during southern spring. Although often observed without filters, they are best seen in blue or violet light when they are high in altitude and in yellow or green light at very low altitudes. Other orographic clouds are observed over the Elysium Shield.

In addition to the dramatic orographic clouds, Mars exhibits many localized discrete clouds. These rotate with the planet and are most often found in northern spring-summer in Libya, Chryse, and Hellas. One remarkable example of a discrete topographic cloud is the "Syrtis Blue Cloud," which circulates around the Libya basin and across Syrtis Major, changing the color of this dark albedo feature to an intense blue. Originally named the "Blue Scorpion" by Fr. Angelo Secchi in 1858, this cloud usually makes its appearance during the late spring and early summer of Mars' northern hemisphere. It has been prominent during the 1995 and 1997 apparitions and is best seen when the Syrtis is near the limb. Viewing this cloud through a yellow filter causes the Syrtis to appear a vivid green (yellow + blue = green).

Limb brightening - or "limb arcs" are caused by scattered light from dust and dry ice particles high in the Martian atmosphere. They should be present on both limbs often throughout the apparition and are also best seen in blue-green, blue or violet light. When dust is present, these arcs are often conspicuous in orange light.

Morning clouds - are bright, isolated patches of surface fog or frosty ground near the morning limb (Mars' western edge as seen on Earth's sky). The fogs usually dissipate by mid-morning, while the frosts may persist most of the Martian day, depending on the season. These bright features are viewed best with a blue-green, blue, or violet filter. Occasionally, very low morning clouds can be seen in green or yellow light.

Evening clouds - give the same appearance as morning clouds but are usually larger and more numerous than morning clouds. They appear as isolated bright patches over light desert regions in the late Martian afternoon and grow in size as they rotate into the late evening. They are best seen in blue or violet light.

The size and frequency of limb clouds appear to be related to the regression of the northern, rather than the southern, polar cap. Both limb arcs and limb clouds are prominent after aphelion (70° L_S), but limb clouds tend to rapidly decrease in frequency after early summer, while limb hazes become more numerous and conspicuous throughout the northern summer.

Equatorial Cloud Bands (ECB's) - These features appear as broad, diffuse hazy bands along Mars' equatorial zone and are difficult to observe with ground-based telescopes. HST has revealed that these clouds may be more common than we have suspected in the past. Their prevalence during the 1997 apparition led some conferees at the Mars Telescopic Observations Workshop-II (MTO-II) to postulate that many limb clouds are simply the limb portions of ECB's. ALPO astronomers are encouraged to watch for these elusive features during the 2001 apparition. Are they really more common, or could it be that our improved technologies merely allowing us to detect them more easily?

ECB's are best detected visually through a deep-blue (W47 and W47B) Wratten filters and may be photographed or imaged in blue or ultraviolet light.

New technologies, such as CCD cameras, sophisticated computer hardware and software, and large-aperture planetary telescopes have given rise to a virtual explosion in advanced techniques of studying our Solar System. Never before have we been able to readily detect the delicate wispy Martian Equatorial Cloud Bands so well as we do now with CCD imaging.

Dust storms - Recent surveys, including our Martian meteorology study, have shown that dust events can occur during virtually any season [Martin and Zurek, 1993. Beish and Parker, 1990]. The main peak (285° L_S) occurs during Mars' southern summer, just after southern summer solstice, but a secondary peak has been observed in early northern summer, around 105° L_S. Classically, the storms occurring during southern summer are larger and more dramatic: they can even grow rapidly to enshroud the whole planet. It should be remembered, however, that these global dust storms are quite rare — only five have been reported since 1873, and these have all occurred since 1956. Much more common is the "localized" dust event, often starting in desert regions near Serpentis- Noachis, Solis Lacus, Chryse, or Hellas. During the 1997 apparition, CCD and HST observations revealed localized dust clouds over the north polar cap early in northern spring.

Identifying the places where dust storms begin and following their subsequent spread is most important to future Mars exploration missions. The following criteria apply in the diagnosis of Martian dust clouds:

1. The sine qua non of Martian dust clouds is movement with obscuration of previously well-defined albedo features. Absence of this criterion in the present study disqualified a candidate from inclusion under dust clouds.
2. They must be bright in red light. In the past, astronomers have identified Martian dust clouds and/or obscurations as "yellow clouds." It is incorrect to describe the color of Martian dust clouds as "yellow." While they may appear yellowish when observed without the aid of color filters, they are in fact brighter in red and orange light than they are in yellow light. Dust clouds brighten faintly in yellow filters and display well-defined boundaries through orange and red filters. During the initial stages of formation, they often appear very bright in violet and ultraviolet light, suggesting the presence of ice crystals. We vigorously discourage the use of the term "yellow clouds" to describe dust. If a suspect cloud is not bright in red light, it is not to be considered a dust cloud.
3. There are numerous reports of anomalous transient albedo features appearing near dust clouds, especially when the solar phase angle was reasonably large. When these clouds reach heights of several kilometers, they may cast shadows that are observable from Earth. Dr. Richard McKim (BAA) has written an excellent review of Martian dust storms [McKim, 1996].

Blue Clearing - Normally the surface (albedo) features of Mars appear vague through light blue filters, such as the Wratten 80A. With a dark blue (W47) or violet (380-420 nm) filter, the disk usually appears featureless except for clouds, hazes , and the polar regions. When a little-understood phenomenon known as the "blue clearing" occurs, however, Martian surface features can be seen and photographed in blue and violet light for periods of several days. The clearing can be limited to only one hemisphere and can vary in intensity from 0 (no surface features detected) to 3 (surface features can be seen as well as in white light). The Wratten 47 filter or equivalent is the standard for analyzing blue clearing.

Recently there has been renewed professional interest in blue clearing. We encourage ALPO Mars observers to watch for this phenomenon during the 2001 apparition.

THE INTERNATIONAL MARS PATROL

The International Mars Patrol (I.M.P.) is an international cooperative effort between individual observers and members of observing groups located around the world. Established in the late 1960's, by Charles F. ("Chick") Capen, the I.M.P. has contributed more than 30,000 observations of Mars. Contained within the archives of the A.L.P.O. Mars Section library are the records of fifteen apparitions of Mars covering a span of 36 years.

During the 1980's and early 1990's the I.M.P. participated in professional activities providing observers for Lowell Observatory's International Planetary Patrol and provides quality photographs of Mars to the United States Geological Survey for creating maps of albedo features of the Red Planet. However, due to Federal budget cuts these programs have been severely limited to a narrow scope and amateur participation has all by disappeared.

The I.M.P. coordinates and instructs the cooperating observers in using similar visual, photographic (film and electronic), photometric, and micrometric techniques employing color filters and standard methods for reporting their observations. The chronological filing of this large quantity of data requires the observation information obtained for each night Universal Date be recorded on one or two standard observing report forms!

Each apparition the A.L.P.O. Mars Section receives thousands of individual observations consisting of visual disk drawings made with the aid of color filters, black-&-white and color photographs, intensity estimates of light and dark albedo features, color contrast estimates, and micrometer measurements of polar caps, cloud boundaries, and variable surface features during the 10 to 12 month observing period. The chronological filing of this large quantity of data requires the observation information obtained for each night Universal Date be recorded on one or two standard observing report forms!

It is with this regard that the A.L.P.O. Mars Coordinators have prepared a simple, efficient and standard Mars observing Report Form. This Standard Form, or its format, can be used for reporting all types of observations such as; micrometry, transit timings, intensity estimates, etc. Photographs may also be attached to the top or back of the form and the relevant information blanks to be filled in at the telescope. Planetary aspects blanks can be filled in at other times than while observing [Capen et al, 1981].

Observational data consist of color filter photography, visual disk drawings, visual photometry (intensity estimates on the standard ALPO scale: 10 = polar brightness, 8 = desert mean brightness, 0 = night sky), micrometry, and CCD imaging. Great emphasis is placed on quality photographs in red, blue, and violet light, full disk drawings using standard color filters, polar cap measurements made with the astronomical micrometer, and with modern observing techniques such as full disk photometry and CCD imaging.

THE MARS WATCH OBSERVING PROGRAM

The Marswatch program was initiated in electronic form in 1996 through the collaboration of astronomers at Cornell University, the JPL Mars Pathfinder Project, and the Mars Section of the A.L.P.O. as a vehicle through which Mars astronomers worldwide can upload their observations to a WWW home page and archive site at JPL.

MarsNet is the WWW arm of the International Mars Watch, a group founded by professional astronomers interested in Mars to facilitate better communication between the amateur and professional Mars observing communities. At those Internet sites, you will find images of Mars contributed by amateurs and professional, tools to aid you in planning your own Mars observations, current and past issues of the International Mars Watch Electronic Newsletter, and links to other Mars-relevant sites on the Internet. The primary purpose of this project is frequent CCD imaging of Mars using B,V,R or other standard filters and visual drawings and photos in order to monitor the planet's atmospheric dust and cloud activity.

Secondary goals include imaging or spectroscopic characterization of the surface color and mineralogy, characterization of the growth and retreat of the polar caps, and analysis of atmospheric water vapor content. Because Mars rotates at nearly the same rate as the Earth and it also has a dynamic atmosphere that exhibits hourly, daily, and seasonal changes, frequent observations from observatories spanning the widest possible range of longitudes are desired.

The upcoming apparition (2001) is particularly important because the U.S. Orbiter (Mars Global Surveyor) will be continuing to routine imaging during this time. In addition, the orbiter will be in a low sun-synchronous polar orbit, so it will only "see" the surface of Mars around 2 a.m. and 2 p.m. local time (the rest of the planet is over the horizon), so quality ground-based observations are needed in order to place these single-time-of-day orbiter views of the planet as well as the single-location lander data, into a global context.

The project will maintain a WWW home page and archive site in association with the Mars Pathfinder mission. The goal will be to have participants submit one or more of their images (or entire data sets if they like) to this site for dissemination to NASA Project personnel, professional astronomers, amateur astronomers, news and print media, educators and schoolchildren, and the general public. Another general project goal is to post at least one new CCD image of Mars on the Web every day between November 2000 and January 2002. Even better would be one "daily global view" per day, composed of 2 or 3 Mars images taken on the same night but from observatories widely separated in longitude. To make this a reality will require a dedicated and geographically-diverse network of observers.

Figure 1. A Graphic Ephemeris for the 2001 Aphelic Apparition of Mars showing the apparent diameter (solid line) in arc-seconds, 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 (dash-dot line) in areocentric degrees. The areocentric longitude (L_S) of the Sun, shown along the right edge of the graph defines the Martian seasonal date. The value of L_Sis 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. Graph prepared by C.F. Capen

CALENDAR OF EVENTS: MARS — 2001

DATE	LS	POINTS OF INTEREST
2001 Jan 25	107.3°	Mars at 6" apparent diameter. Apparition begins for observers using 4-inch to 8-inch apertures telescopes and up. Begin low resolution CCD imaging. Views of surface details well defined. Northern hemisphere early summer. NPC in rapid retreat? Are limb arcs increasing in frequency, intensity. Use filters! Antarctic hazes, hood? Cloud activity high?.
2001 Mar 05	125°	Mars at 8" apparent diameter. Maria Acidalium broad and dark. Bright spots in Tempe-Arcadia-Tharsis-Amazonis regions? "Domino effect" appears around 120° - 125° LS.
2001 Mar 29	137°	Mars at 10" apparent diameter. Quality conventional photos possible with high resolution telescope. Both polar caps visible, haze canopy?
2001 Apr 16	146°	Mars at 12" apparent diameter. Mid-summer. Northern clouds frequent. Syrtis Major broad. Are both polar hoods visible?
2001 Jun 13	176°	Mars at Opposition and 20.4" apparent diameter. Late southern winter. NPH and SPH present. Does SPH or frost cover Hellas? W-clouds present?
2001 Jun 20	180°	Mars at Northern Autumn Equinox (Southern Spring Equinox). South Polar Cap (SPC) maximum diameter, subtending ~65° latitude. North Polar Hood present.
2001 Jun 21	181°	Mars at Closest Approach and 20.79" apparent diameter. South cap emerges from darkness of Winter. SPH thinning.
2001 Jul 07	190°	SPC should be free of its hood. Possible W-clouds in Tharsis-Amazonis. Wide Syrtis Major shrinks on eastern border. NPH bright.
2001 Jul 24	200°	SPC shrinking. Syrtis Major continues to shrink. W-clouds possible. Apparent diameter 18.2".
2001 Aug 09	210°	SPC develops dark Magna Depressio at 270° longitude; -80° latitude. Syrtis Major narrows rapidly. W-clouds? At 215° LSa dark rift, Rima Australis, appears connected with Magna Depressio from 20° to 240° longitude; and SPC develops bright projection at 10° - 20° longitude in Argenteus Mons. Dust cloud in Serpentis-Hellaspontus?
2001 Aug 26	220°	Bright SPC projection Novissima Thyle 300° - 330° longitude. Dark rift Rima Augusta connected from 60° to 270° longitude. W-clouds possible. Dust clouds? Apparent diameter 14.1".
2001 Sep 11	230°	Rapid regression of SPC. Bright elongated Novissima Thyle reaches from SPC and becomes the isolated Novus Mons (Mountains of Mitchel). Rima Australis broadens, and Magna Depressio becomes dusky feature. Syrtis Major retreats on Easterner. North Polar Hood prominent.
2001 Sep 26	240°	SPC rapid retreat. Novus Mons small, bright, and high-contrast. Rima Australis widens. SPC isolated bright spot at 155° longitude? Any white patches near -20° latitude may brighten, Atmosphere of Mars very clear, LS 240° - 250°. Occasional morning limb hazes. Apparent diameter 11.2".
2001 Oct 12	250°	Mars at Perihelion. SPC in rapid retreat, ~20° in diameter. Novus Mons smaller. Dust clouds expected over Serpentis-Hellaspontus (LS 250° - 270°). Syrtis Major narrow. W-clouds possible.
2001 Oct 28	260°	Novus Mons reduced to a few bright patches and soon disappears. Hellas bright spots? Numerous bright patches. Windy season on Mars begins, dust clouds present? Mars 9" apparent diameter.

MOTION OF THE CENTRAL MERIDIAN OF MARS

Add the following degrees to the Ephemeris CM values below.

HR	DEGREE	HR	DEGREE	MIN	DEGREE	MIN	DEGREE
1	14.62	13	190.07	1	0.24	10	2.44
2	29.24	14	204.69	2	0.49	20	4.87
3	43.86	15	219.31	3	0.73	30	7.31
4	58.48	16	233.93	4	0.97	40	9.75
5	73.10	17	248.55	5	1.22	50	12.18
6	87.72	18	263.17	6	1.46
7	102.34	19	277.79	7	1.71
8	116.96	20	292.41	8	1.95
9	131.58	21	307.03	9	2.19
10	146.20	22	321.65
11	160.83	23	336.27
12	175.45	24	350.89