Mars and its Satellites


Mars, the red planet. Fourth closest to the sun and named after the Roman God of War. Half the size of Earth and a lot colder. A desolate, barren land with only a few really distinguishable features, the Tharsis bulge, the Elysium Plateau, the two polar caps and the Valles Marineris. A wind swept, dusty desert with little atmosphere, and not much gravity. What are Mars’ secrets? Is there life? Could humans ever live on Mars? Does Mars have water, and is the air breathable?

Quick Factfile:

  • Mars, the red planet is the fourth planet from the sun.
  • In the time of ancient Romans, people named the planet Mars, after Mars, the god of war, because its colour reminded them of blood.
  • Mars has two natural satellites (moons). These are named Phobos and Deimos.
  • Phobos and Deimos were named as they are because in mythology, Phobos (fear) and Deimos (panic, terror) were the sons/secretaries of Mars/Ares (the Greek version of the Roman Mars).
  • Deimos is the smallest known moon in our solar system.
  • The reason that Mars is red is because of the high iron content of the planet’s crust. Over the years, this has reacted with oxygen and water in the air to form rust (a red substance that corrodes metals).
  • Sometimes Mars has dust storms that cover the entire planet.
  • Mars is colder than Earth as it is further away from the sun. A warm day on Mars is equivalent to a cold day on Antarctica.
  • Mars’ scientific planet symbol looks like a spear and shield, again form Mars/Ares.
  • Mars’ day is almost exactly the same length of time as Earth’s day. Earth’s day has a length of 23 hours 56 minutes long. Mars’ day is 24 hours 37 minutes and 23 seconds.
  • The tilt on the axis of these two planets, Mars and Earth is about the same - 24 degrees.
  • For a long time, people believed that intelligent life forms existed on Mars, these were called Martians. One of the more famous Martians is Marvin, a Warner Bros creation. According to Marvin, the Earth is a waste of space as it blocks the view of Venus!
  • In 1938 in America, an actor named Orson Welles presented a radio play done in broadcast style about aliens landing in a small New Jersey town. Hundreds of people panicked, believing this to real, and left town, or locked themselves in their homes with their rifles!

Mars in General:

Size of Mars:

Mars is approximately half the size of Earth, with a diameter of 6,786 kilometers, compared to Earth’s 12,756 kilometers.

Surface Landscape:

From Earth, Mars looks red, this due to oxidation on the surface. Mars’ rock landscape contains high percentages of the element Iron, and as this corrodes, it turns red. Mars, like Earth, has two poles, one at the North, and one at the South. Like glaciers, the poles extend and contract along Mars’ cold surface. While the polar caps mainly consist frozen water, in the Martian winter, frozen carbon dioxide, more commonly known as ‘Dry Ice’ is deposited on the surface of these caps. The cap at the South pole is 300 kilometers wide, and at the North pole, the cap is over three times as large, being 1000 kilometers wide. The true thickness of these caps is not truly known, but it is possible that the ice and frozen gases on these caps have a thickness of 2 kilometres.

Mars’ surface has many rocks and is covered in dust. Carbon Dioxide winds have been known up whip up dust storms that cover the entire planet from time to time. The dust from these storms (which occur between late spring and early summer in the Southern hemisphere of Mars) is very fine, and takes a long time to settle. Mars is basically a desolate and barren landscape, with no known plants.

There are dry riverbed channels all over Mars, which shows that the red planet once had flowing water, and possibly seas. This proves that Mars once had warmer temperatures and higher pressures. Now, however, the water has gone, but some scientists believe some of it could be underground.

The red planet’s surface has both valleys and volcanoes. There have been two major centres of past major volcanic activity found, known as the Elysium Plateau and the Tharsis bulge. Olympus Mons (Mount Olympus) is the biggest volcano on Mars, and is one of four giant volcanoes located on the Tharsis bulge. It is nearly three times higher than Mount Everest, Earth’s highest mountain above sea-level. Olympus Mons has a base diameter of 600 kilometers and has an elevation of between 25 and 27 kilometers above the average ground height (there is no sea-level). Though there has been no sign of recent volcanic activity anywhere on Mars, scientists cannot be certain that all the volcanoes are extinct.

Mars doesn’t seem to have any tectonic plates, as there are no folded mountain belts or ‘Marsquakes’. A seismometer on board Viking 2 (Mars space probe from America) failed to detect any seismic activity, but scientists cannot rule out the possibility of plates, as some bulges and faults have been discovered by various probes.

Interestingly, Mars has a extremely thick surface crust, between 5 or 6 times as thick as Earth’s. Mars’ crust has a thickness of 200 kilometers. Another amazing feature of Mars’ surface is the Valles Marineris, a canyon system that is the longest and deepest (known) in the solar system. It is over 4,000 kilometers long and up to 10 kilometers deep.

Two huge basin structures down in the Southern hemisphere in the highlands are called Hellas and Argyre. Hellas has a diameter 1,500 kilometers and a depth of 7, and Argyre is 800 kilometers across and 2 kilometers deep.

Structure of Mars:

Mars has its rocky and dusty crust, which is 200 kilometers thick, then an extremely deep rocky stratum layer, and finally a metallic core or nucleus. Studies show that the metallic core is not likely to be liquid, as Mars doesn’t have a magnetic field.

Mars’ Atmosphere:

The atmosphere of Mars is nearly completely carbon dioxide, at 95%. There is also 2.7% nitrogen, 1.6% argon, 0.2% oxygen and minute amounts of water vapor, carbon monoxide and other noble (inert) gases. If humans ever went to Mars, they could not breathe without assistance from equipment, as carbon dioxide in concentrated form is poisonous to humans.

Martian Climate:

As Mars is, at all times, further away from the sun than Earth, it does not receive as much heat. This makes a warm summer day on Mars colder than the coldest regions on Earth, like Antarctica at our South pole. Amazingly, due to thin atmosphere, Mars’ temperatures can change by 100 degrees Celsius in one day. The warmest Mars ever gets is about -43 degrees Celsius, and the coldest is about -123 degrees Celsius. Mars’ average temperature has been recorded as -55 degrees Celsius.

Mars in the Solar System:

In terms of our planets, Mars is not big. Mars is the fourth planet from the sun, and therefore colder than Earth. It is the last of the small planets before the giant planets start with Jupiter. Mars is half the size of Earth, and twice as big as Earth’s natural satellite, the moon.

Mars’ orbit is elliptical, and the planet takes 687 Earth days (1.88 Earth years) to orbit the sun once. The planet Mars spins on a 24-25 degree axis, basically like Earth, and therefore has two cold poles, one in the North and one in the South. This angle of axis produces seasons quite like Earth's, although every season is quite a bit colder. Mars’ orbit lies 1.5 times as far away from the sun as Earth’s. At Mars’ closest point in its orbit around the sun, it is 206.7 million kilometers away from the sun. At its orbit’s furthest distance, it is 249.2 million kilometers. The reason why Mars’ year is longer than Earth’s is that it takes Mars almost twice as long to orbit the sun once than Earth.

Mars' History with Men:

Men and Mars. The relationship started thousands of years ago, with people first looking into the sky. The ancient Romans named the planet after their God of War, as the rusty colour reminded them of blood. Only when telescopes really started examining the planet, though, did people really start to know some of Mars’ secrets.

  • In 1609, Johannes Kepler discovered that Mars’ orbital path around the sun is not circular, but elliptical, like a squashed circle.
  • In 1610, Galileo first used a telescope to view Mars. He recorded its phases.
  • By the late 1600s, other scientists had already discovered that its day was about the same length as ours, that its polar caps change with the seasons and that dark areas could be distinguished. They thought these dark areas were seas, but we now know that they are to do with weather cycles.
  • In the late 1700s, an astronomer named William Herschel saw bright patches that looked like clouds, and hypothesised that Mars had an atmosphere.
  • In the late 1800s, an Italian astronomer named Giovanni Schiaparelli noted linear markings that got termed canali. For more information, see about Life on Mars.
  • Phobos and Deimos, the Martian Satellites were discovered by Asaph Hall in 1877.


Phobos is one of Mars’ two natural satellites (moons). Phobos is a small but heavily cratered lump of rock that is roughly ‘potato’ shaped that orbits Mars. It is many scientists belief that Phobos was once a asteroid that flew too close to Mars and was captured by gravity than a naturally occurred satellite.

Phobos has an average diameter of 20-28 kilometers. Its dimensions are roughly 27 x 21.5 x 19 kilometers.

A huge and well known crater on Phobos is named Stickney after Angela Stickney’s maiden name. She was married to Phobos’ discoverer, Asaph Hall. After searching for a sign of any Mars satellites for many days, he told her that he was giving up. She encouraged him to try for one more night, and sure enough, that night Phobos was discovered!

Phobos is about 4,800 kilometers from the planet, and 9,378 kilometers from the planet’s core. It takes Phobos 7 hours and 39 minutes to orbit Mars once.

Some scientists believe that one day, Phobos will break up into lots of smaller chunks of rock, and form a ring of rock around Mars, still on the same orbit ring.

From the surface of Mars, Phobos has a brightness of a very bright star on Earth’s light multiplied several times.


Deimos is the smallest known satellite in our solar system. Like its partner Phobos, Deimos is roughly potato shaped. Deimos has a diameter of 10-16 kilometers. It is about 11 x 12 x 15 kilometers.

Deimos’ orbital period around Mars is longer than Phobos’ as it is further out. It takes Deimos 30 hours and 18 minutes to orbit the planet once.

Deimos’ surface is heavily sprinkled with craters, a lot more so than Phobos. Scientists also believe that Deimos, like Phobos, is a captured asteroid.

Deimos is found about 20,000 kilometers away from the planet Mars, and its brightness from the surface of Mars would be the equivalent of the planet Venus at night to us.

A Recent History of Mars & Men:

What we really know about Mars is basically thanks to the United States of America’s Mariner, Viking and Pathfinder missions over the years. The first Mars space probe, Mariner 4, was launched in 1964, and in July 1965, this probe passed within 9,600 kilometres of Mars’ surface. Mariner 4 took 19 close-up colour photographs of the planet, and beamed these back to Earth, showing that Mars had craters like the moon, a very thin atmosphere (only 1/100 of Earth’s) and no canals made by intelligent species. Mars seemed to hold no life, intelligent or otherwise.

Mariner 4’s ‘sister’ (though up-dated) probes, Mariners 6 and 7, were launched in 1969. These also photographed Mars in flybys, and sent back photographs to NASA.

In 1971, yet another Mariner reached Mars, this time Mariner 9. The probe went into orbit around Mars and mapped the entire planet by photograph. The pictures showed Olympus Mons and the Valles Marineris.

In 1976, two new Mars probes caught the world’s attention. These were a new variety, named Viking 1 and Viking 2. The mission of these probes was not only to orbit mars and take aerial photographs, but also to land on the Martian terrain.

The Vikings managed to discover what Mars’ atmosphere consisted, take temperatures, gather soil samples and analyse them, and finally take many more photographs.

While the Vikings were launched at the same time, they didn’t land in the same place on Mars, but had areas to search quite a long way apart. This was so that the scientists working on the project had different data from different areas to work with.

The soil samples that the two Viking probes obtained showed a high iron content in the soil of Mars and no apparent life. There was no carbon in the soil (carbon is essential for our kind of life) and no microscopic life forms from either of the two landing sites. Although there didn’t seem to be any life, these results could change, as only a tiny percentage of Mars’ regions were tested by the probes.

Finally, in 1997, the Mars Pathfinder mission arrived on Mars. Inside the Pathfinder, there was a tiny robot named Sojourner which was romote-controlled from NASA headquarters. Sojourner tested more soil and took more photographs. It also studied Mars’ rocks in detail. Many of the big rocks near Pathfinder’s landing site have been tested and named, for example Shark, Scooby Doo, Moe, Stimpy and Yogi. Yogi is probably the most famous Mars rock, and the most extensively tested. Two other tested areas are known as the Roadrunner Flats and the Rock Garden. There were still no signs of life on Mars on the Pathfinder mission.

The Feasibility of Life on Mars:

Is anyone home?

For many years, people have associated the red planet with life. Romans with people fighting battles, and the God Mars, science-fiction writers with Martians, Warner Bros with Marvin the Martian, and Martians in general. Why?

Of all the planets in our solar system, mars is the one most like Earth, so therefore it was a reasonable assumption to expect life. So is there life?

In the late 1800s, an astronomer named Giovanni Schiaparelli saw linear markings on the surface of Mars. He named these in Italian, ‘canali’. By this term, he simply meant that there were channels on Mars’ surface, but not canals. Some people began to believe that these ‘canals’ were a sure sign of intelligent life on the red planet - who else could have built them?

Now, of course, we know from the Mariner, Viking and Pathfinder missions that there are no canals built on purpose by any form of life. Why did people see canals? This mistake of astronomy is attributed to a visual illusion in which the dark areas on Mars’ surface seem to be connected lines.

Scientists are slowly piecing together the puzzle of Mars’ history. Once, people believe from the dry riverbeds on Mars’ surface, Mars was warm, with running water. Maybe life could have existed on the planet. Quickly, Mars turned into a hostile terrain. Scientists don’t believe that life could have evolved fast enough to survive, but nobody is yet willing to rule out the possibility of Martians...

Let’s go colonising!

It’s closer and more realistic than it sounds. Quoting the magazine Scientific American, "America has the resources and technology to send men to Mars...". Fair enough, but do the benefits of terran colonisation and exploration justify the dangers of sending people to the red planet?

NASA in America has hinted at a manned expedition to Mars in the year 2020, but there are no final plans. People would have to take oxygen supplies, food and equipment, and it’s a long journey to get there - 9 months! While it is true that men could search a greater area of planet for life, and do detailed tests on rock and soil samples, nobody is sure how well a possible mission would work. Also, a manned mission would cost about the same as 10 robotic missions, so the US Government hasn’t indicated that American men will be setting foot on the red planet any time soon.

It would be possible over a long period of time for men to slowly use a ‘green-house’ effect on Mars, and warm the planet up. This would melt the polar ice caps to produce water. If we added the right ‘ingredients’, or elements, it would be possible for humans to walk, breathe and grow with out assistance, but this is an extremely unlikely event.

Nevertheless, science-fiction fans can keep in their sights the possibility of Martian colonisation, although it would be a cold and barren place to live...

Update! U.S. President George W. Bush has announced that a manned mission to Mars may in fact take place at some point. Election gimmick, malarky, or effective way? Only time will tell...


Mars, the red planet, named after the Roman God Mars, is a cold and hostile environment. There are no obvious signs of life, and no tests indicated any signs of past life having existed. Many space probes have visited the red planet, and discovered that it is very like Earth in its axis tilt, poles, seasons and day. Mars has two natural satellites, Phobos and Deimos, both of which support many craters. Mars has some amazing geographical features, from the towering Olympus Mons to the winding Valles Marineris. Half the size of Earth, and nine months away, Mars is a barren and harshly terrained neighbour.

Apatrix adds: Its connection to the god of war dates back much further. Gugalanna, Nergal and Ares were all associated with it.
Tlogmer says: Mars was named in the time of the greeks, I believe, named Ares, after the greek god of war. The romans later gave new names to the greek gods when they adopted them as their own, and therefore new names to the planets.


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  • New Scientist - September 1997
  • National Geographic - August 1998
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