John Pazmino
 NYSkies Astronomy Inc
 2010 January 4
    Mars in his orbit around the Sun passes by Earth once in about two 
years and seven months. When he lines up with Earth and Sun, he is 
near his closest distance from Earth. Mars and Earth are then on the 
same side of the Sun in their orbits. 
    From Earth's eye, Mars is on the line from Sun thru Earth to Mars. 
To see Mars we face away from the Sun, so this aspect of Mars relative 
to Sun and Earth is called opposition. At other times we look toward 
various angles away from the Sun, but not directly opposite, at 180 
    Mars has an orbit more elliptical than Earth's. His distance from 
Earth at opposition varies widely by almost 2:1 between the closest 
approach when Mars is nearest to the Sun as he passes Earth and when 
he is farthest from Sun. The effect of this varying distance near 
opposition is that Mars, which already is a small planet, presents a 
tiny disc to us in small telescopes. It is tough enough to inspect the 
planet when he is at a close opposition, but in 2010 he rounds an 
opposition near the farthest possible distance away. The disc is then 
about the smallest. 
Watching Mars 
    All of this article assumes only bare eye and binocular viewing. 
No telescope of high magnification is discussed here. Just about any 
binoculars are suitable, so long as it produces clear sharp images. 
Dirty, banged-up, loose instruments should be repaired or discarded. 
Now binoculars costing mid tens to low hundreds of dollars are thoroly 
adequate. Expensive units are simply not needed. 
    The binoculars should be comfortable and light and small to easily 
support by hand. Large heavy models require support like a camera 
tripod. They are clumsier to handle and less spontaneous to use. 
    Have a star atlas by which to plot Mars among the stars. An all-
0sky starchart or a simple constellation chart has too few stars and 
too small a scale. A US letter size chart with Castor-Pollux on the 
right and Regulus on the left has a good scale. To avoid spoiling a 
good book of maps, work with photocopies. 
    In 2010 Mars spends his prime time between stars Castor and Pollux 
and Regulus. A planetarium program or mechanical planisphere shows 
where in the sky these stars are. They are in the evening sky fro 
January thru late spring, but in different directions and altitudes 
above the horizon. No other planet invades this region to confuse with 
    In an elliptical orbit, the point closest to the Sun is the 
perihelion; farthest, apohelion. This is also spelled 'aphelion' but 
the tendency is to pronounce the 'ph' as a 'f', at least in English. 
The word is 'app-HEH-lee-yonn', not 'a-FEH-lee-yonn'. Leaving the 'o' 
in place forces the better pronunciation by separating the 'p' and 
'h', 'a-poh-HEH-lee-yonn'. 
    Because in 2010 Mars is near apohelion at opposition, this round 
is known as an apohelic opposition. The disc of the planet attains 
only 14.1 arcsecond diameter, the size of a US 25-cent coin seen from 
350 meters away! This is tiny in the typical home telescopes. Most 
home astronomers will see little texture on the planet. 
    In the months before and after the opposition date, the planet 
shrinks in size to a pink dot in most home telescopes. That's why most 
home astronomers storm their views of Mars within the week or so of 
opposition. That's when the disc is largest with better chance of 
discerning his surface features. 
    This round of Mars may be a downer in the telescope if you recall 
the close-in, perihelic, oppositions, of 2001, 2003, and 2005. 
    Much of the news about Mars is produced by the several spaceprobes 
at or on Mars. More news comes from ground or Earth-orbit 
observatories. Follow Mars developments thru the websites of the 
facilities and missions. 
    The two rovers, Spirit and Opportunity, are still working after 
SIX YEARS on the planet. Spirit is still jammed in loose soil while 
Opportunity is running freely. Efforts to free Spirit so far have 
failed, but JPL is exploring further attempts. 
    The orbiting probes, like Mars Express and Mars Recon Observer, 
are in good working order with a dense stream of information beamed 
back to Earth. 
    NASA's Mars Science Lab and Russia's Phobos-Grunt probes were not 
ready in time for the 2010 opposition. They had to be launched a 
couple months ahead of the opposition, in fall 2009. They are nearly 
complete, and will be ready in early 2010 but they missed the current 
launch window. The next launch window to visit Mars is near yearend 
2011, before the 2012 opposition. 
    During the 2010 opposition Mars is in his northern spring and 
summer. The south hemisphere of Mars is in autumn and winter. The 
north pole of Mars is tilted toward Earth, letting us to see it in the 
clear and the Sun to heat it. 
Mars geography
    You really should use the pure word, 'areography' by analogy with 
mapping of Earth. It is increasingly common to use Earth terms with a 
qualifier for the instant celestial body. You will hear and see 'Mars 
geology' in place of 'areology' and 'Mars geophysics; for 
'areophysics'. The prefix comes from the Greek name for Mars, Ares. 
    The light and dark spots and blotches on Mars, as seen from Earth, 
were originally thought to be seas and land. They were given names 
still in use today. The regions are coarse areas of the planet, the 
size, in proportion, to entire countries on Earth. 
    Spacecraft visited Mars and observed topographic features: plains, 
mountains, canyons, craters, cliffs, river beds, and so on. These were 
named separately from the dark/light names. In some cases a vague 
patch seen from Earth is part of a real landform on Mars. In such 
cases, the new name was made from the old. Nix Olympica, a white spot 
on Earthly maps, is really the ice and snow on top of a huge volcano, 
now named Mons Olympus. 
    Thus, Mars has two independent systems of place names! The ones on 
Mars maps for Earth use (ground or close orbit) have the light/dark 
names. The light/dark scheme is also the 'albedo' scheme, based on the 
reflective property of the various parts of the planet. Those for use 
at or on Mars have the topographic names. 
    In both systems, the names are Latin or Latinized words, requiring 
at the worst a continental pronunciation. Saying them like English 
words can result in nonsense sounds. 
    One amazing fact is that the land area of Mars, which is the 
entire area of his globe, is quite equal to the land area of Earth! 
Recall that while Earth has four times the total global area as Mars, 
only a quarter of it is land. The rest is open water. 
Mars seasons 
    Mars has a regime of seasons analogous to Earth. With no open 
water and only a thin atmosphere, Mars does not have the same weather 
mechanism as Earth. 
    When Mars's north pole is titled toward the Sun, and in view of 
Earth, the north hemisphere enjoy spring and summer. With the pole 
tilted away from Sun, and from Earth, the north hemisphere is in 
autumn and winter. The difference among seasons is mainly of raw 
influx of solar radiation and ground temperature. 
    The seasons are roughly twice the length of Earth's, due to the 
Mars year being about 2 Earth years. On Earth, the seasons are about 
of equal length, because the orbit of Earth is nearly circular and 
Earth travels in it at about the same speed all year long. The Mars 
seasons vary widely in length due to the more excentric orbit of the 
planet. The planet spends a greater or lesser time in each season 
according as the varying speed of the planet in his orbit. 
Time and calendar
    As yet there is no global system of calendar or time for Mars. 
many schemes are proposed but none earned general favor over an other; 
As an example, the two Mars rovers count elapsed Mars days starting 
from their own landing on the planet. Opportunity started work a 
couple days after Spirit, making their day counts out of synch. A 
common name for a day on Mars, or on any other planet, is 'sol'. 
    Most schemes skip dividing the Mars year into anything like weeks 
or months. These units on Earth are based on the Moon's phases or 
cultural legacy, both lacking on Mars. It seems best to merely assign 
a say count within each year, as is done for data networks and payroll 
management. As yet there is no agreement for a zero year. 
    One common method of giving the place of Mars in his orbit, 
amounting to a Mars calendar date, is to cite the longitude of the Sun 
along the Mars ecliptic. This parallels the method on Earth where the 
location of the Sun on Earth's ecliptic is the date within the Earth 
year. In fact, some starcharts label the ecliptic with both degrees of 
longitude and calendar dates for the location of the Sun. 
    In this system, the Mars vernal equinox is at solar longitude 0 
deg, like for Earth. The summer solstice is 90 deg; autumnal equinox, 
180 deg; winter solstice, 270 deg. 
    The Mars clock hour is based on the actual longitude on Mars, 
there being no timezones. The Mars day is divided into 24 'hours', 
each then cut into 'minutes' and 'seconds'. These units are a trifle 
longer than those of Earth because the Mars day is 24h 37m of Earth 
time, 2.6% longer. 
    This slippage of hours between Earth and Mars causes real 
headaches for scientists working with Mars spacecraft. They must keep 
track of Mars time, yet conduct their work on Earth time! 
    The apparition of a planet is the entire span of time from when it 
emerges from twilight after passing by the Sun to when it is lost in 
twilight before passing the Sun again. There is a dead period when the 
planet is absent from the sky while passing the Sun. In the old days, 
it was impossible to follow the planet in this dead zone, also called 
the 'Sun gap'. 
    With the SOHO spaceprobe photographing the sky around the Sun, you 
can follow a planet on the SOHO pictures! The images are too coarse to 
see any detail on the planet, but you satisfy yourself that the planet 
is moving along as it should. 
    Mars, without the aid of SOHO, resolves out of the morning dawn 
as the Sun leaves it behind in darker sky. It is, due to his distance 
from us, a dim star of 2nd magnitude, a bit tough to discern in a 
bright twilight sky. By convention, the dead zone for Mars is one 
month before and after his conjunction with the Sun. 
    On successive mornings, Mars edges farther from the Sun into 
eventually a night sky, where he is then an obvious new 'star' in the 
zodiac. Mars is gliding eastward thru the zodiac, just like the Sun, 
but at a slower pace. Mars is lagging the Sun, allowing him to be seen 
earlier and earlier in the night as the month roll by. 
    When Mars falls behind the Sun to stand 90 degrees west from him, 
this is west quadrature, or square, or quartile. This moment is 
informally the start of the telescope viewing season for most home 
astronomers. By this time Mars is close enough to Earth to present a 
reasonably large (still small!) disc in the telescope and maybe 
something can be seen of his surface markings. 
    Mars continues to fall behind the Sun until he seems to slow his 
forward march and enter the retrograde loop. This is explained more 
fully below. All the while, the planet is drawing nearer to Earth, 
growing larger in angular size and in brilliance. He is already a 
magnitude 0 or brighter star, outshining other stars around him. 
    The opposition moment is in the middle of the retrograde loop, 
when he is running westward at the fastest pace. He is then 180 
degrees west (or 180 east) of the Sun, as directly as possible 
opposition in the sky from the Sun. 
    Mars at opposition is near his largest angular size and 
brilliance. This maximum of size and brightness is a peak that within 
a week is noticeably weakened. Most home astronomers storm their 
observing within a week or so of opposition. 
    After opposition Mars runs a bit farther west, then slows and 
stops. He then leaves the retrograde loop, resuming direct, east, 
motion again. he is moving a bit slower than the Sun, so the Sun is 
now catching up to Mars, decreasing the spacing between the two 
    Mars eventually stands 90 degrees east of the Sun, in east 
quadrature, and informally ends the telescope viewing season for this 
apparition. He is still a bright star by eye but his disc is rather 
too small for easy detection of surface details. 
    Mars slowly creeps along the zodiac with the Sun gaining on him. 
He shrinks in size and wanes in luster. He remains a considerable star 
in the zodiac, easy to spot until twilight engulfs him. 
    Eventually the twilight glow around the Sun catches up to Mars, 
pulling him into the dusk sky. And then Mars is swallowed in strong 
twilight to end the apparition. By convention this happens a month 
before the next solar conjunction as Mars enters the Sun gap. 
    Mars is visible, if at an inconvenient hour, for quite two years 
of its two years and seven week circuit around the sky. He is lost to 
sight for a month before to a month after sliding around the Sun. 
    One hideous mistake many people make is to WAIT UNTIL the night of 
opposition for their first look at Mars. They also cease looking 
immediately after opposition. Both actions crudelly ruin you of your 
due and owing appreciation of the celestial dance of planets. You 
should watch Mars routinely for several months leading to and from 
opposition. At the very least, cover the interval between the two 
squares, west and east. 
Opposition and proximity
    Often these are treated as equivalent events. If the orbits of 
Mars and Earth were both circular and the planets coursed in them at 
constant speeds, the opposition and proximity would coincide. Due to 
the elliptical shape of the orbits and varying speeds of the planets 
in them, proximity and opposition almost never can coincide. 
    proximity is the linear closest approach of Mars to Earth, the 
point of minimum signal travel time and all that. It occurs on January 
27 with a separation of 99.33 million kilometers, about 2/3 the 
distance from Earth to Sun. The lineup of Mars, Earth-Sun comes on the 
29th, at 99.41 million kilometers. The difference is slight, but the 
two events have entirely distinct definitions. 
    Even at opposition Mars is not exactly 180 degrees from the Sun. 
Mars is a little north of the ecliptic on the 29th, so is a wee bit 
off the earth-Sun line. The separation from the Sun is a maximum, more 
like 178 degrees, but not quite 180. For convenience sake, we work 
only with the longitude of Mars, his downrange distance along the 
ecliptic, and ignore his displacement in latitude north or south of 
the ecliptic. So Mars is at opposition when his longitude is 180 
degrees from the Sun's, not when he is actually 180 degrees away. 
Retrograde loop 
    All of the planets do a really sturrange act once during each of 
its cycles around the sky. They all after proceding eastward thru the 
zodiac, slow down, stop, backtrack westward. They run westward for a 
while at a fast pace. Then they slow again, stop, reverse, and resume 
direct motion. 
    This is the retrograde loop. The effect is entirely one of 
perspective from Earth. We view mars, a moving planet, from Earth, an 
other moving planet. The line of sight from Earth to Mars swings to 
and fro according as the relative speeds between the two planets. 
    The two inner planets Mercury and Venus go thru their loops in 
twilight or daylight. We just don't notice them. Mars and the other 
outer planets go thru their loops in night, where we can marvel at 
    The loop is run during the weeks leading to and from opposition. 
Mars entered the loop on 2009 December 22. He is in retrograde at 
opposition in the middle of the loop on 2010 January 29. On 2010 March 
11 he comes out of retrograde and takes up prograde motion again. 
    The term 'loop' implies a circle or lasso shape. In fact the path 
traced out in the stars varies substantially from opposition to 
opposition. It ranges from a loose 'S' shape, to an aerobatic up-&-
over or down-&-under curve, to a lazy back-&-forth sway. In 2010 it's 
an up-&-over, a bit flattened, curve.
    In all cases there is a definite point at each end, a cusp or 
vertex or apex, where the planet shifts direction from east to west or 
west to east. These points are the 'station' points, because for a day 
or two Mars is standing still. 
    When Mars is within the loop, running westward, he is nearest to 
Earth and largest in angular size. In space, this part of the loop is 
actually closer to Earth, like looking at a turntable from its side. 
The leads to and from the loop are farther away. Mars outside the loop 
is much dimmer and smaller. 
Mars in 2008-2011 
    Altho this article is written in January 2010, the tables here 
give the principal events for the entire circuit of Mars from the 
previous conjunction with the Sun to the next. This gives a complete 
view of the behavior of the planet. 
    Dates and hours are jimmied for the best view from New York. Dawn 
events are in the east toward the sunrise point; dusk, west, sunset 
point. You may better understand the movement of Mars by watching two 
days before the event date thru two days after it. 
   NYC date    | hour | event 
   2008 Dec  5 |  --  | conjunction with Sun 
   2009 Jan  5 | dawn | emerges from dawn, start of apparition  
   2009 Jan 27 | dawn | 4 deg S of Mercury 
   2009 Feb 17 | dawn | 1 deg S of Jupiter 
   2009 Mar  3 | dawn | 1 deg N of Mercury 
   2009 Apr 21 | dark | 6 deg S of Venus 
   2009 Apr 20 |  --  | perihelion, 1.38146 AU Sun 
   2009 Apr 21 | dark | 4 deg S of Venus 
   2009 Jun 21 | dark | 2 deg N of Venus 
   2009 Jul 12 | dark | 5 deg S of Alcyone 
   2009 Jul 26 | dark | 4 deg N of Aldebaran 
   2009 Aug 12 |  --  | increase to +1.0 magnitude 
   2009 Aug 20 |  --  | ascending node, north of ecliptic 
   2009 Oct  7 | dark | 6 deg S of Pollux 
   2009 Oct 24 |  --  | increase to +0.5 magnitude 
   2009 Oct 27 |  --  | vernal equinox, northern spring begins 
   2009 Oct 29 |  --  | west square, magn +0.5, diam 7.8sec 
   2009 Nov  1 | dark | inside Beehive cluster 
   2009 Nov 26 |  --  | increase to +0.0 magnitude 
   2009 Dec 19 |  --  | increase to -0.5 magnitude 
   2009 Dec 20 |  --  | begins retrograde westward in Cancer 
   2009 Jan  9 |  --  | increase to -1.0 magnitude 
   2010 Jan 27 |  --  | proximity, 0.66399 AU, 99.33 million km 
   2010 Jan 29 |  --  | opposition, 0.66456 AU, mag -1.3, diam 14.1sec 
   2010 Feb  5 | dark | 3 deg N of Beehive cluster 
   2010 Feb 17 |  --  | decrease to -1.0 magnitude 
   2010 Mar  4 |  --  | decrease to -0.5 magnitude 
   2010 Mar 11 |  --  | resumes prograde eastward in Cancer 
   2010 Mar 23 |  --  | decrease to -0.0 magnitude 
   2010 Mar 29 |  --  | apohelion, 1.66594 AU Sun, 1.00674 AU Earth 
   2010 Apr 15 |  --  | decrease to +0.5 magnitude 
   2010 Apr 17 | dark | 1 deg N of Beehive cluster 
   2010 May  4 |  --  | east square, magn +0.8, diam 7.1sec 
   2010 May 18 |  --  | decrease to +1.0 magnitude 
   2010 Jun  7 | dark | 1 deg N of Regulus 
   2010 Jul 23 |  --  | decrease to +1.5 magnitude 
   2010 Jul 30 | dark | 2 deg S of Saturn)-convention Venus-Saturn 
   2010 Aug 19 | dark | 2 deg N pf Venus ) 
   2010 Sep  6 | dark | 2 deg N of Spica)-convention Spica-Venus 
   2010 Oct  6 | dusk | 6 deg N of Venus) 
   2010 Oct  1 |  --  | in dusk, sets at nightfall 
   2010 Nov 11 | dusk | 4 deg N of Antares 
   2010 Nov 13 |  --  | autumnal equinox, northern fall begins 
   2010 Nov 21 | dusk | 2 deg N of Mercury 
   2010 Dec 12 | dusk | 1 deg S of Mercury 
   2010 Jan  9 |  --  | immerges into dusk, end of apparition 
   2011 Feb  9 |  --  | conjunction with Sun 
    For the most part, telescopic viewing of Mars pretty much ends 
when he reaches the east square, standing 90 degrees east of the Sun. 
He fades slowly there after and is far less prominent among the stars. 
In spite of this waning luster, Mars configures with Venus and Saturn 
and then with Spica and Venus in fall 2010 for a last hurrah. 
Mars and the Moon 
    The table below gives the conjunctions of Mars with the Moon. 
Because the Moon moves so swiftly thru the stars, the conjunction can 
unravel on the previous or next day and can even be loose on the event 
day as seen from New York. The age, elongation, and offset to Mars are 
for the actual conjunction, and can only approximate the situation 
when the pair is visible from New York many hours away. 
    NYC date    | hour | Mars | Age  | Elong | Phase  
    2008 Dec 26 | dawn | 5d S | 29.1 |   6 W } new Moon 
    2009 Jan 24 | dawn | 4d S*| 28.5 |  15 W | waning crescent 
    2009 Feb 23 | dawn | 6d S | 27.8 |  21 W |    | 
    2009 Mar 24 | dawn | 4d S | 27.3 |  23 W |    | 
    2009 Apr 22 | dawn | 6d S | 26.9 |  32 W |    | 
    2009 May 21 | dark | 7d S | 26.5 |  38 W |    | 
    2009 Jun 19 | dark | 6d S | 26.0 |  44 W |    | 
    2009 Jul 18 | dark | 5d S | 25.3 |  58 W |    | 
    2009 Aug 16 | dark | 3d S | 24.6 |  60 W |   \|/ 
    2009 Sep 12 | dark | 1d S | 23.9 |  69 W | -------
    2009 Oct 12 | dark | 1d N*| 22.8 |  92 W | 3rd quarter 
    2009 Nov  9 | dark | 3d N | 21.8 |  98 W | 3rd quarter 
    2009 Dec  6 | dark | 5d N | 19.9 | 113 W | waning gibbous 
    2010 Jan  2 | dark | 7d N | 17.6 | 145 W | waning gibbous  
    2010 Jan 29 | dark | 7d N | 14.8 | 179 E | full Moon 
    2010 feb 25 | dark | 5d N | 11.8 | 146 E | waxing gibbous 
    2010 Mar 24 | dark | 5d N |  9.6 | 117 E | waxing gibbous  
    2010 Apr 21 | dark | 5d N |  8.0 |  97 E | 1st quarter 
    2010 May 19 | dark | 5d N |  6.7 |  81 E | 1st quarter  
    2010 Jun 16 | dark | 6d N |  5.6 |  68 E | waxing crescent 
    2010 Jul 15 | dark | 6d N |  4.8 |  58 E |    | 
    2010 Aug 12 | dark | 6d N |  3.9 |  48 E |    | 
    2010 Sep 10 | dusk | 5d N |  3.2 |  40 E |    | 
    2010 Oct  9 | dusk | 4d N |  2.5 |  31 E |    | 
    2010 Nov  7 | dusk | 2d N |  1.8 |  22 E |   \|/       
    2010 Dec  6 | dusk | 1d S*|  1.4 |  15 E | -------    
    2011 Jan  4 | dusk | 5d S |  0.7 |   8 E | new Moon 
    2011 Feb  2 | dusk | 7d S |  0.1 |   0 E | new Moon
    The starred entries under 'Mars' are instances where the Moon 
passes right over the planet for a rare occultation. None of these is 
observable from New York because they occur when the Moon is down. We 
must be satisfied with only an approach or reproach of the tow bodies. 
It is a happy feature that the current apparition starts and ends with 
such a hiding behind the Moon! 
    As a practical matter conjunction with the Moon can't be seen well 
at all until the elongation is about 20 east or west of the Sun and 
the ecliptic is inclined steeply to the local horizon to get the Moon 
to higher altitude and darker twilight. 
Other attractions 
    About halfway between Castor-Pollux and Regulus is the Beehive 
star cluster. This is in downtown Cancer, a constellation of dim stars 
usually missed in a sky with luminous graffiti. This cluster is about 
2 degrees across and appears as a misty spot in dark skies. In 
binoculars the Beehive resolves into a couple dozen stars. The group 
is about 590 lightyears away. 
    Mars retrograde loop circulates among three bright planetary 
stars! Pollux, Algieba (gamma Leonis) and rho1 Cancri have their own 
planets. rho1 Cancri needs binoculars to see well while Pollux and 
Algieba are naked-eye targets. 
    You will not, of course, see the planets, but the fact you can see 
the stars induces a wonder if the folk up there are gazing back at us. 
    Castor is the closest system of SIX stars. It stands 52 lightyears 
away and has three pairs of stars. Two pairs are close together to 
combine their light into the Castor you see in the sky. The third pair 
is very dim with no contribution to the luster of Castor. Binoculars 
show Castor only as a single point with no hint of its detail.
    Oppositions of Mars are exciting events to watch, even if you 
don't got a telescope. In fact, for this 2010 round, a telescope may 
present you with a poorly defined pink dot. Yet to the eye and 
binoculars Mars is a brilliant visitor in Cancer, gyrating thru his 
retrograde loop. Later in 2010 he jives with other planets on his way 
into twilight around the Sun.