- Facts about Mars - - - Planets, Mars, Jupiter, Saturn, Pluto, Venus, Mercury, Neptune, Uran

The planet Mars has been a source of fascination for mankind for eons. Twinkling orange-red in the sky, Mars is a similar planet to Earth, as it has a solid surface of rocks and soil, mountains and valleys, riverbeds and canyons. However, Mars at the present time is in deep freeze, where temperatures can reach only freezing during the day in the warm places and can plummet to unimaginably cold temperatures at night or near the poles. The atmosphere consists of mostly cold, dry carbon dioxide with small amounts of nitrogen, argon, krypton, carbon monoxide and other trace gases.

Mars has been visited by many NASA spacecraft: orbiters, landers and rovers. A list of successful missions to the planets (including Mars missions) is listed in Table 1. The first spacecraft to visit Mars was Mariner 4 which flew by in 1965. It took 22 pictures of Mars from a distance of ~6000 miles. It showed that the 'canals" supposedly seen by Earth-based observers in telescopes were not real but simply optical illusions. The planet was found to have a cratered, barren surface, and an thin atmosphere with a pressure of around 7 millibar. Mariner 4 was looking at the more cratered southern hemisphere. Later missions showed more geologically younger parts of the planet with maria, valleys and smoother areas, indicating more active geology happening at an earlier time in Mars' history.

Spacecraft to Mars:

Mariner 4 (flyby) Mariner 6 and 7 (twin flybys) Mariner 9 (orbiter)

The next pair of missions, Mariner 6 and 7 did further studies and sent back more pictures and data. The first spacecraft to actual go into orbit around Mars and stay there for awhile was Mariner 9 in 1971. This spacecraft did pioneering studies of Mars and was the first to observe a dust storm in the atmosphere. In fact, when Mariner 9 first reached Mars, a dust storm was going on and the surface was almost completely obscured. Nothing could be seen except for 4 spots. These turned out to be the 4 largest volcanoes on Mars which were high enough to have their peaks above the dust storm. These were: Olympus Mons (the highest mountain on Mars), Ascraeus Mons, Arsia Mons and Pavonis Mons. These are shield volcanoes that are currently dormant.

Once the dust storm subsided, Mariner 9 stayed in orbit for 11 months and took thousands of pictures and measurements of Mars, studying its canyons, river systems, craters, volcanoes, atmosphere, clouds, mountains and bringing humanity to a new level of understanding of this fascinating world.

Table 1: Successful NASA Missions to the Planets

Spacecraft Planet Date of Arrival

Mariner 2 Venus 1962

Mariner 4 Mars 1965

Mariner 5 Venus 1967

Mariner 6 Mars 1969

Mariner 7 Mars 1969

Mariner 9 Mars - orbit 1971

Pioneer 10 Jupiter 1973

Mariner 10 Mercury - Venus 1974

Pioneer 11 Jupiter - Saturn 1974 (Jupiter), 1979 (Saturn)

Viking 1 Mars 1976

Viking 2 Mars 1976

Voyager 1 Jupiter - Saturn 1979 (Jupiter), 1980 (Saturn)

Voyager 2 Jupiter - Saturn - Uranus - Neptune 1979 (Jupiter), 1981 (Saturn), 1986 (Uranus), 1989 (Neptune)

Magellan Venus 1991

Galileo Jupiter - orbit 1995

Mars Global Surveyor Mars 1996

Pathfinder Mars 1997

Mars Odyssey Mars 2001

Mars Exploration Rover Mars 2004

Cassini Saturn 2004

Mars Reconnaisance Orbiter Mars 2006

Phoenix Mars 2008

In 1976, the Viking spacecraft was sent to Mars. It consisted of an orbiter and a lander. Two Vikings were sent, Viking 1 and Viking 2. The Viking 1 lander thrilled the world when it touched down on the Martian surface on July 20, 1976. The cameras showed a reddish rocky landscape with a pink, hazy sky. It was truly alien looking. The lander was equipped with tools and instruments to study the surface. It had geological and biological experiments. The biological experiments were designed to detect life (or at least find organic materials). The geologic experiments studied the rocks and minerals and soil. The Viking 1 lander landed in a place called Chryse Planitia (Chryse Plain. Chryse means “the land of gold”) The Viking 2 landed on September 3, 1976 on another part of the planet called Utopia Planitia (Utopia Plain).

View of Mars surface from Viking Lander

No spacecraft were sent to Mars after this for another 20 years. The Mars Global Surveyor mission went to Mars in 1996 and did a fabulously detailed study of Mars from orbit, taking tens of thousands of pictures over the next 10 years in greater detail and coverage. The following year, in 1997, the Pathfinder lander was launched and put a smaller rover on Mars. This landing galvanized space explorers everywhere who, by 1997, were able to follow the mission on the World Wide Web. The little rover was enclosed in a landing platform from which it was able to drive away and explore its neighborhood. Pathfinder took measurements of rocks and studied the mineralogy of Mars.

In 2001, the Mars Odyssey was sent to Mars. This spacecraft provided a much needed data relay link for the next Mars missions which were the two Mars Exploration Rovers launched to Mars in 2003. These much bigger and more sophisticated rovers both landed on Mars in January of 2004. They have done spectacular explorations of Mars and are still exploring today (2007). They have sent back thousands of images from the surface and traveled many miles farther than their designers had expected. The missions were expected to last 3 months after which the rover parts would have been assumed to have failed. Two years after landing, both rovers are still going strong.

The most current mission is called Mars Reconnaisance Orbiter which reached Mars on March 10, 2006. It is also currently exploring Mars with the most high-resolution spectral instruments which will tell us about the chemistry and physics of the Martian atmosphere and surface.

** See our Triton Fun Science Newsletter for articles about Mars:

May 2006 issue: Nuclear Physics on Mars