The American Association of Amateur Astronomers

Serving the Amateur Astronomy Community ONLINE since 1996

The Solar System Data Page

The Sun
Top of Solar System Data Page
AAAA Home Page

Online Store


Search AAAA

The AAAA Universe
Start Here

The AAAA Online Store

Join the AAAA

Control Center
Site Table of Contents

AAAA Members
  Reports and Activities

Frequently Asked Questions

to Astronomy Sites

News from the AAAA
Press Releases and News Updates

An Overview of Astronomy
A Concise Guide to the Universe

The Solar System
Planetary Data Page

The Constellation 
Home Page
Data, Myths and Background

Arp Peculiar Galaxies
A CCD Image Gallery

The American Astronomer 
The AAAA  Newsletter Online

Observing Programs
from the  Astronomical League 

Club Discount
on Magazine Subscriptions

Members of the AAAA Team

The American Association of Amateur Astronomers 
AAAA Mission Statement

Special Offer
A Primer for Beginning Astronomers

Astronomy Information from Sky&Telescope via Electronic Mailing List

AL Observing Programs in PDF Format

AL Observing Programs in Adobe Acrobat PDF Format

Join the AAAA's FREE Online Discussion Group, Hosted by Yahoo's eGroups Service

P.O. Box 7981
Dallas, TX 75209-0981


Learn the Constellations
The First Light Astronomy Kit from David Chandler Company
Buy it Now or 
Find Out More



  • Mars is the 4th planet from the Sun.
  • The planet Mars has a diameter of 4200 miles.
  • At a distance of 141 million miles, it takes 687 days to circle the Sun.
  • One day lasts 24 hours, 24 minutes of Earth time.

Mars 2001 NASA Composite Photo Good views of Mars occur every other year. Best views occur when most favorable opposition takes place, every 15 or 17 years. This happens when Mars is in opposition during the months of August or September. Mars' period of revolution around the Sun is about two years. 

This NASA photo of Mars is a composite created with images snapped by the Mars Global Surveyor. The picture is a made up of color strips taken on nine successive orbits from pole-to-pole over the planet in March 1999. The color in this picture is computer-enhanced and is not as it would appear to the human eye.


Learn the details of the 2018 Opposition of Mars on the AAAA Activities Page

Learn about the Mars Hoax and how you can help

Mars at Opposition

Mars Opposition - 2018

Mars will come into Opposition on July 28, 2018, in the constellation Capricornus, when it will shine at an apparent visual brightness of -2.78 mag. Four days later, on July 31, 2018, it will have its closest approach to Earth during this apparition, with a distance of only 35.994 million miles (57.59 million km, 0.38496 AU), and an apparent diameter of 24.31". This will be the closest approach since the record opposition of 2003, and become comparatively close only in 2031. Mars will not be this close again until the opposition of 2287.

Learn more at SEDS

Mars Opposition - 2005

During October and November 2005, Mars will be just as bright as it was during the opposition of 2003, but, this year, the time frame is shifted to autumn.

Mars will be rising in the east around midnight during July and August. By October, it will be rising at sunset. Once above the horizon, it will be the brightest object in the sky, a bright red-orange "star". It will be brighter in a pair of binoculars, but you will need a telescope to see any detail.

Mars Opposition will be in early November, which means it will be directly overhead at midnight, local time, on November 7.

As your read about the 2003 Opposition of Mars, keep in mind that most of this information, except for the dates, also applies to the Opposition of 2005.

Mars Opposition - 2003

During August 2003, Mars, the Red Planet, will be closer to Earth than it has ever been before in recorded history. On the date of closest approach, August 28, 2003, Mars will be only 55.8 million kilometers from Earth, little more than 1/3 of an Astronomical Unit (AU). An astronomical unit is the average distance from the Earth to the Sun, about 165 million kilometers. This will be the closest together Mars and Earth have been in the last 50,000 years!

Oppositions of Mars 1988-2003

Oppositions of Mars 1988-2003 by C.F. Chappin

This chart by C.F. Chapin shows the relative positions of Mars and Earth for the years 1988 to 2003. The last great opposition of Mars was 1988. On August 28, 2003, Mars will be at its closest approach to Earth in recorded history, at a distance of only 34,646,418 miles.

Click on image for enlarged view

2003 - A Great Year to Observe Mars

While the orbit of Earth around the Sun is very nearly circular, the orbit of Mars is not. During opposition, when the Earth and Mars lie in line with the Sun, the distance between the two planets varies considerably from year to year depending on Mars’ position in its orbit. If Mars comes to opposition when it is farthest from the Sun (at aphelion), it will lie 61 million miles from Earth. But if Mars reaches opposition when it is closest to the Sun (at perihelion), it will lie only 34.6 million miles from Earth. Perihelic oppositions occur every fifteen to seventeen years. In August and September 2003, Mars will reach perihelic opposition again.

Because of the way Mars’ orbit is located in space, the very closest oppositions occur when we see Mars against the stars of Sagittarius and Scorpius, the southernmost constellations on the ecliptic. Thus, the best oppositions occur when Mars is too far south for good viewing in the Northern Hemisphere. This is what happened in 1988: the opposition was very close, but Mars was low in the sky in the northern hemisphere. But in 2003, Mars will be higher up, the light from Mars will reach us via a shorter path through Earth’s atmosphere, and we will have a better, sharper view of the planet during the current opposition.

Planning for the Public

In planning any special Mars observing activities for the general public or the media during the 2003 opposition, keep in mind that in late August when Mars is closest (diameter about 25 arc sec), it will only rise about 30 degrees above the horizon at midnight ... so not good for "early evening" observing. However, this situation improves through September: at end of September, Mars will still be over 20 arc sec. in diameter, but will cross the meridian (a bit more than 30 degrees high) earlier ... about 9:30PM. This placement is somewhat better for public programs.

As always, there is the danger of planet-wide dust storms at this perihelion. Storm activity on Mars will easily wipe out any surface features otherwise visible.

The Planetary Society has proclaimed August 27, 2003, the date of opposition, as "Mars Day". The Planetary Society has a goal of "half of the world's population looking at, or thinking about, Mars" on Mars day. So please circle this day on your calendar. Now is the time to start planning Mars Parties in your local area.

During the June 21, 2001 opposition,  Earth and Mars came within about 42 million miles (67.3 million kilometers) of each other, the closest they had been since 1988 when they came within 37 million miles (59 million kilometers) of each other. Throughout the summer that year, and until October when it finally set, Mars was prominent in the southern sky, visible in the constellation of Scorpius, and just to the left of Antares. As the space between Earth and Mars narrowed, even observers using small, 4 to 6 inch telescopes were able to make out some of the Martian features, including clouds, surface markings and polar caps. Unfortunately, this opposition waw marred by extensive dust storms on the surface of the planet, obscuring sufrace details from view for most of the opposition.

The Mars viewing gets even better in coming years. On August 27, 2003, Earth will swing to within 34.6 million miles (55.7 million kilometers) of Mars. On that date, the Earth-Mars distance will be the smallest it has been in at least 50,000 years. During the 2003 opposition, Mars will be located in the constellation Aquarius.

During the Spring of 1999, Mars could be found in the constellation Virgo, very bright and up most of the night. It was in opposition to Earth and at closest approach on May 1, 1999. 

During the month of June, 2000, Mars was in conjunction with Saturn behind the Sun, and was not visibile from Earth.

Facts about Mars

A . Mars is named after the Roman god of war. It is about half the size of Earth, with about one-tenth the mass. In some ways, Mars is much like the Earth. It has a similar rotational period and its yearly orbit is only twice that of Earth’s. However, Mars is much colder than Earth, and its small size has affected its ability to retain an atmosphere.

B. Mars' atmosphere is very similar in composition to that of Venus, but much thinner. It is thinner because Mars has a very small gravitational field, and hence cannot hold onto light gasses. The thin CO2 atmosphere therefore does not contribute greatly to any greenhouse effect. Mars does have polar ice caps which are composed of a combination of water ice and carbon dioxide ice (dry ice).

C. The dried-out river channels on Mars give evidence that Mars did in fact once have water on its surface. When Mars was cooling after its initial formation, water vapor was probably outgassed. The water then condensed into clouds and rained down to the surface to form rivers and lakes. In addition, large quantities of water could have been released in the form of mud slides and the like. The lack of an ozone layer, however, means that the water molecules could be easily broken up into their constitutive elements, and these gasses could escape Mars' small gravitational field. Therefore, Mars now has no water existing in the liquid state. However frozen water exists in the polar ice caps and as permafrost beneath the surface.

D. Mars has a very thick outer crust. This determines many of its geological features. The largest volcano in the solar system is on Mars, the Olympus Mons. Its base is approximately the size of the state of Missouri, and it is more than twice as tall as the largest volcano on Earth. The largest valley in the solar system is also on Mars. In a region called Tharsis, a massive bulge about 10 Km above the surface has formed. Near this bulge is the Valles Marineris (named after the Mariner Space Probe which discovered it). The Valles Marineris is long enough to reach from New York to Los Angeles, and is at some spots, over 4 miles deep. The Tharsis bulge and the Valles Marineris are thought to be causally related to one another.

E. Mars is red because it has a great deal of oxidized iron on the surface; i.e. because it is rusty.

F. Mars has two small moons, Phobos (fear) and Deimos (panic). Deimos is the smallest cataloged satellite in the solar system.

Oxidized crystalline rocks on the surface of Mars give it it's tinged blood-red color. It was natural that the ancient observers linked it with combat and war. The Babylonians called Mars as Nergal, their God of War. Ares was the brave, quarrelsome but arrogant Greek God of War. His two sons Phobos and Deimos (Fear & Panic) accompanied Ares. Appropriately, both the moons of Mars are named after them. The only other red object in the night sky is a red star in the Scorpio constellation that was named Antares (Anti-Ares). However, the Roman god Mars enjoyed the portfolio of both War and Agriculture. So important was Mar to the Romans that the first month of the Roman year was named March after Mars. Its no wonder that, even for ancient Indians, Mangal (Mars) represents anger, aggression, ambition, courage, lust for power, roguery etc. Hindu marriage is not complete without the Mangal sutra; a necklace made from blood red corrals. 

Mars is the only planet in the Solar System besides the Earth that has polar ice caps. Made of water ice and carbon dioxide, these ice caps expand and recede seasonally like those on Earth. In the middle of the 19th Century astronomers described Mars as a hospitable place for life forms.

Manoj Pai, Ahmedabad, Gujurat, India

Earn The Astronomical League's Award for Observing the Solar System

Planetary Club Rules and Regulations

Comparative Data on the Terrestrial Planets






Equatorial diameter (Km)





Density (kg/m')





Mass (Earth-1)





Surface gravity (Earth=1)





Escape velocity (km/s)





Mean distance from sun (Au)





Mean distance from sun (miles)





Mean distance from sun (10(6) Km)





Orbital period (Earth years)





Orbital period (Earth days)





Orbital velocity (Km/sec)





Avg. Surface Temperature (K)





Tell Your Friends the Benefits of Joining 
the American Association of Amateur Astronomers!

Hit Counter

Join the American Association
of Amateur Astronomers.

P.O. Box 7981
Dallas, TX 75209-0981