Mars, the red planet -- the other one about which so much has been guessed and so many science fiction stories have been written. But there are no Martians on Mars; no little green men. Nevertheless, Mars is a fascinating planet and our probes are still sending us back pictures.


Mars is only about half the size of Earth (it is the second smallest planet in our solar system), with a diameter of 4250 miles. This means its gravity is also less than half of Earth's -- it is 0.4 Earth's gravity. However, its axis tilt is about the same. Earth's is 23.5 degrees, and Mars' is 25 degrees.

axis tilts


Mars is 1.52 AU from the sun, and so its year is longer than any of the other inner planets, lasting 687 Earth days. It's day is about the same length as ours, though, at about 24.5 hours. So it spins on its axis at almost the same rate Earth does even though it is much smaller and farther from the sun. Because its days are close to the same, its temperatures, while colder than Earth's due its distance from the sun, are still within a range we can understand. Temperatures there range from a high of about 70 degrees F. to a low of about -220 degrees F.

Since Mars has an axis tilt about the same as ours, it also has seasons. There are ice caps on the poles that melt back when each pole is at its 'summer,' and facing the sun. The ice caps are made of layers of water ice and carbon dioxide ice. When astronomerrs first saw the ice caps and how they melted seasonally, they were quite sure there were waters flowing through channels away from the poles. What they found later, however, was that the ice was simply vaporizing, and not becoming liquid. This transition from a solid state directly to a gas state is called subliimation. We see it happen with 'dry ice' which is carbon dioxide ice.


Mars' atmosphere is less than 1% as dense as Earth's. It is made up of 95.3% carbon dioxide, 2.7% nitrogen, and 2% other gases, including argon and water vapor.

We do see occasional clouds on Mars, and our probes have told us they are made up of water ice crystals. We have also seen massive dust storms. These yellow/orange storms are huge and can sometimes cover almost the whole planet. There are also phenomena which have been dubbed "rocket dust storms" in which "blobs" of dust shoot upward very rapidly, as the article and video Crazy Alien Weather: Lightning-Filled Rocket Dust Storms of Mars explains.

All Mars dust storms are powered by sunshine. Solar heating warms the Martian atmosphere and causes the air to move, lifting dust off the ground. The chance for storms is increased when there are great temperature variations like those seen at the equator during the Martian summer.

...Surprisingly, many of the dust storms on the planet originate from one impact basin. Hellas Basin is the deepest impact crater in the Solar System. It was formed ...when a very large asteroid hit the surface of Mars. The temperatures at the bottom of the crater can be 10 degrees warmer than on the surface and the crater is deeply filled with dust. The difference in temperature fuels wind action that picks up the dust, then storm emerge from the basin.

from "Mars Dust Storms" by Jerry Coffey (note: ellipses mark where the standard explanation and timing of the event were and this is a matter of dispute)


Mars storm


Surface Features


The terrain at the poles is different from elsewhere on the planet. The poles exhibit the youngest strata since they are the products of yearly deposition and erosion. Both the north and south ice caps are layered: dust, water ice, and carbon dioxide ice. In the winter, carbon dioxide freezes out of the atmosphere, producing a thin coating of carbon dioxide ice over the water ice. At the same time, however, the summer on the opposite hemisphere is producing the dust storms which coat the planet, and so there is a layer of dust being deposited during a pole's winter as well. Below left is a photograph of the dust-covered ice at the north pole. Below the ice caps are sand dunes, on the lower part of the picture. The great stretches of sand dunes which surround the north pole completely obscure everything beneath them. The picture on the right shows a side-on clear view of the layering.

Mars ice layers ice cap layers
The north polar ice cap is about 2 miles thick. The canyons and troughs are about half a mile deep.
The dark lines are dust.


The north polar cap is the largest and is primarily water ice. Both ice caps will show some melt-back and erosion effects during summer for each (when it is winter for one, it is summer for the other, just like on Earth). Interestingly, both polar caps have spiral appearances as seen from above.

Mars north pole Mars south pole
Mars North Pole -- 750 miles across in winter
Mars South Pole (the spiraling is not as distinct) -- 260 miles across in winter



Mars labeled:

The orange areas,such as Arabia Terra and the Amazonis Planitia are desert areas which are soil and sand covered. A NASA spokesman has stated, "If you look at the soil composition of Mars, the one thing that really strikes you is that it's 5 to 14 percent iron oxide," said Dr. Peter Curreri, a materials scientist at NASA's Marshall Space Flight Center. "It's almost ore-grade material."

The following quote is from a NASA website that appears to be down:

What we know of Martian soil composition comes from the Viking landers, and from spectral analysis of light reflected from dust storms in the Martian atmosphere. The Vikings detected iron-rich smectite clays, magnesium sulfate, iron oxides, and reactive oxidizing agents of unknown chemistry. They detected no organic compounds. Spectral analysis of the dust storms identified the smectite clay as montmorillonite which expands when it contacts water, and contracts when it dries. Silicate minerals, oxides (mostly iron), and some calcium carbonate were also found.

Mars soil composition has 5-14 % iron oxide. It is rich in iron, covered with rust thus making it red. The most prevalent elements in the soil patch were silicon and iron. It also found significant levels of chlorine and sulfur. A mineral called olivine was also found.

At Spirit’s landing site, the most prevalent elements in the soil patch were silicon and iron. It also found significant levels of chlorine and sulfur, characteristic of soils at previous martian landing sites but unlike soil composition on Earth. A NASA spokesman stated "There may be sulfates and chlorides binding the little particles together." Those types of salts could be left behind by evaporating water, or could come from volcanic eruptions, he said. The soil may not have even originated anywhere near Spirit's landing site, because Mars has dust storms that redistribute fine particles around the planet. The greatest mystery may be the identity of the oxidizing agent or agents in the soil. There is some debate as to exactly what this substance may be. It is known to be a highly oxidizing substance that releases oxygen when it is wetted.

The red desert areas are primarily the "northern plains." They are depressed areas, something like the maria on our moon. We can see drainage channels leading into them, indicating there was a lot of water there at some time in the past.

drainage channels, Mars

It is important to remember the colors are false and the blue is NOT water! Many craters can be seen in these areas.

The water that, sometime in the past, drained into these low-lying areas came from the interior of the planet. They probably formed a northern ocean which was then evaporated by later lava extrusions.

A system of gigantic ancient valleys -- some as much as 200 kilometers wide-- lies partly buried under a veneer of volcanic lava flows, ash fall and wind-blown dust in Mars' western hemisphere. New observations made with Mars Orbiter Laser Altimeter on the Mars Global Surveyor spacecraft reveal northwestern slope valleys (NSVs) northwest of the huge martian volcano, Arsia Mons, and south of Amazonis Planitia, site of a postulated ocean.

The northwestern slope valley system is ten times larger than Kasei Valles, the largest previously known outflow channel system on Mars, said James M. Dohm of the University of Arizona. The best explanation is that they were formed by catastrophic floods that at their peak potentially discharged as much as 50,000 times the flow of the Amazon River, Earth's largest river, Dohm said. Smaller outflows flooded the valleys later in martian history.

Dohm and others from the University of Arizona Department of Hydrology and Water Resources, UA Lunar and Planetary Laboratory, NASA Jet Propulsion Laboratory, U.S. Geological Survey-Flagstaff and Smithsonian Institution reported the discovery in the June 2001 issue of the Journal of Geophysical Research.

"The implications of uncovering such a significant flood record of the ancient martian past is of great significance in that such activity supports northern ocean (s) and (or) large paleolakes in the northern plains," the researchers wrote.

At sustained peak discharge rates, floods through the valleys would have filled a large ocean (96 million cubic kilometers) hypothesized for northern Mars in about 8 weeks, and a smaller ocean (14 million cubic kilometers) in the same region in about 8 days, according to the scientists' calculations.

The large ocean is equivalent to about a third the volume of the Indian Ocean, or more than three times the volume of the Mediterranean Sea, Caribbean Sea, South China Sea and Arctic Ocean combined. The smaller ocean is equal in volume to the Arctic Ocean. (from an article in Science Daily, August 9, 2001)


  from an article in Time, March 11, 2013:

The new study, led by geologist Gareth Morgan of the Smithsonian Institution in Washington, DC, relied on new readings returned by NASA‘s Mars Reconnaissance Orbiter (MRO), which has been circling the Red Planet since 2006. Some of the spacecraft’s most intriguing surveys have involved the dry sea-beds, riverways and flood channels etched all over the planet, which testify to a wet and turbulent past. ... That, at least, is the conclusion to be drawn from the waterways that can be seen, but there are some that can’t be. Mars has flowed with lava as well as water over its long life, and the tracks cut by floods have sometimes been be covered up by eruptions. One of the most mysterious of the obscured waterways is the Marte Vallis formation in the planet’s northern hemisphere. All that’s visible of Marte Vallis is its outflow channel, but where it begins, how deep it is and how old it is have been mysteries. MRO, however, can look straight through the lava, thanks to its Shallow Radar (SHARAD) system.

The SHARAD imager has been used before, but principally to study the polar caps. This was the first time mission planners had used it to study ancient flood patterns, and that turned out to be a very good idea. For starters, Marte Vallis is a lot bigger than anyone realized—about 600 mi. (965 km) long, 62 mi. (100 km) wide and 260 ft. (80 m) deep. The depth, especially, was a surprise. “This is about twice what we had thought,” says Morgan, “and the channels could be deeper still.”

... The ruggedness of the waterways also suggest that the flooding played out quickly and violently, on the order of weeks or months.

The biggest surprise, though, was the source of all the water. The prevailing theory had been that a large lake or a small sea had breached its barriers and spilled over the surrounding landscape. ... The alternative explanation for Martes Vallis was that Marsquakes or volcanoes had cracked open the ground above subsurface reservoirs and released the water. “A fracture system could have been responsible,” says Morgan, “but in the past, the fractures we could see nearby did not cut across the region.”

The SHARAD readings changed that. The telltale cracks, it turns out, indeed radiate precisely where they should to produce the kind of flood the channels suggest. “The floods, fractures and lava could all be linked to underground forces,” says Morgan.

Mars flood

By mapping the buried channels, researchers discovered the ancient gigantic floods that probably created Marte Vallis apparently originated deep underground from a now-buried portion of fissures known as Cerberus Fossae. [from "Ancient Mega-Flood on Mars Revealed"]


Mars has the biggest volcano and the largest canyon system in the solar system.

Olympus Mons

Olympus Mons

Just in case Olympus Mons looks like a little bump on Mars to you, please notice the curvature of the planet behind it...

Olympus Mons is a shield volcano sixteen miles high (three times the height of Everest), and the base of the volcano is 370 miles across. The crater at the top is a collapsed caldera which is the size of Rhode Island -- about 45 miles across. There is a cluster of volcanoes to the east of Olympus Mons and they are all part of what is called the Tharsis Uplift.

Tharsis Uplift

The Tharsis Upllift (or Tharsis Rise) is dome-shaped bulge about 3.5 miles high and about 2000 miles across.

Mars topography


On the upper left of the above map of Mars is the Utopia Basin. On the lower right of that basin you will see the Elysium Volcanic Field. Elysium Mons is the major volcano in that area. This is part of another uplift -- large and dome-shaped, about 3 miles high and almost a thousand miles wide.

The map above is not one side of Mars, it is pictured as though the planet itself were 'unwrapped' and put onto a flat sheet. There is something important to note when you remember that. On the lower left is the large Hellas Basin. It is a giant impact site, 1430 miles across and 5.6 miles deep. This impact's pressure wave went through the planet. If you remember the Caloris Basin on Mercury, you will remember that on the opposite side of that small planet, the shock wave of that impact resulted in the "weird terrain." A more violent reaction occurred on Mars due to the much stronger and larger impact. It was the Tharsis Uplift that resulted from this hit. When you 're-wrap' the map above, you will find that the Hellas Basin is exactly opposite the Tharsis Uplift.

This happened at another point, too, which you can see above. On the lower right of the map there is a sort of green oval. This is the Argyre Planitia, or Basin. It is another impact site. It is 1120 miles across and 3.2 miles deep. Exactly opposite it is the Elysium Volcanic Field and its associated uplift. So we see on Mercury, Earth and Mars that violent impacts have caused shocks to go through the planets and have resulted in evidence on the opposite side of the planet.

Going back to the map we have been discussing:

Mars labeled


The northern plains which we know were flooded with water at an earlier date, were flooded because they were depressed areas. They were depressed due to a series of impacts, as shown below:

Mars impact basins

This major series of impacts was the result of something called the Late Heavy Bombardment which came in from the Kuiper Belt, long before the planet between Mars and Jupiter broke up. These hits produced the massive craters which later flooded with water when Asteroid Planet began breaking up, producing the Hellas and Argyre crater basins.

After the flood, magma was outpoured from the interior, probably due to hits from the breakup of the asteroid planet. The magma outpoured into the lowland areas, and we can see where it covered the water drainage channels. The heat from the molten magma evaporated the water. However, that water acted with the iron oxide in the magma to form the red rust we associated with the color of Mars now. That combination would have also given rise to the massive amounts of carbon dioxide we find in the Martian atmosphere now.

The series of hits which released so much magma were probably also those which gave rise to the Hellas Basin and the Argyre Basin. Mars was relatively close to that planet and would have received some significant impacts when it broke up. All of the craters in the south have come from the asteroid planet and moon breakup events.

Just south of the Tharsis Uplift is the Valles Marineris, the largest canyon system in the entire solar system. As you can see from the illustration below, it would cross the entire United States, totally dwarfing our Grand Canyon. To the left you will see the three Tharsis volcanoes a little southeast of Olympus Mons.

VM size

A closer photograph gives us a little more detail of part of it:

Valles Marineris


The Valles Marineris measures about an average of 120 miles wide (up to 375 miles in places), 4 miles deep, and about 3100 miles long. We know it was a major drainage channel for the exploding waters, but it also shows distinct signs of electrical discharge activity.

This can be seen in the scalloped sides and the lower line of pit chains next to it. The initial formation was most probably due to a giant split in the crust at the time of the Hellas Basin impact, which resulted in the Tharsis Uplift. Because this was associated with the breakup of the Asteroid Planet, electrical effects would also have been involved, which is why we see the evidence of the electrical discharges. These formations are more clearly explained in the article on crater formation. Evidence for both types of craters is found all over the planet.

Below is a good photograph of the pit chains on Mars caused by electrical machining discharges (which are, basically, the result of lightning discharges which are attempting to equalize positive and negative charges during a disruption).

Mars pit chains


Research on this canyon system is indicating that it may be a very large transform fault, and one that shows indications of horizontal slippage. We highly recommend the short, and lay-friendly, article from physicsworld on this. However we strongly disagree with the last part of the article which indicates the long ages involved on Mars and the 'slow and gradual' processes involved.

Mars outflow channels

The illustration above shows several things in excellent detail. First, however, remember that the colors were added -- blue is not water (it is lowlands), green is not pastures, etc. You can see the very, very straight line of the Valles Marineris which does give evidence of a separation of two crustal plates, as well as giving apparent evidence of slippage along that fault line. The smaller parallel canyon sections just to the north of the main canyon are also indicative of crustal plates breaking and slipping past each other. As the fault itself ends, there is evidence of previous lake formation and then the drainage of the entire area into the Northern Lowlands. The multitude of craters give evidence of both impacts and electrical machining.


Blueberries! Well, that's what they're called, anyway. Take a look:

Rover tracks and blueberries

Mars Rover tracks over a field of "blueberries"

Blueberries are evidence of water in the past as NASA explains in an article on the web.

A major ingredient in small mineral spheres analyzed by NASA's Mars Exploration Rover Opportunity furthers understanding of past water at Opportunity's landing site and points to a way of determining whether the vast plains surrounding the site also have a wet history.

The spherules, fancifully called blueberries although they are only the size of BBs and more gray than blue, lie embedded in outcrop rocks and scattered over some areas of soil inside the small crater where Opportunity has been working since it landed nearly two months ago.

Individual spherules are too small to analyze with the composition-reading tools on the rover. In the past week, those tools were used to examine a group of berries that had accumulated close together in a slight depression atop a rock called "Berry Bowl." The rover's Mössbauer spectrometer, which identifies iron-bearing minerals, found a big difference between the batch of spherules and a "berry-free" area of the underlying rock.

"This is the fingerprint of hematite, so we conclude that the major iron-bearing mineral in the berries is hematite," said Daniel Rodionov, a rover science team collaborator from the University of Mainz, Germany. On Earth, hematite with the crystalline grain size indicated in the spherules usually forms in a wet environment.

Scientists had previously deduced that the martian spherules are concretions that grew inside water-soaked deposits. Evidence such as interlocking spherules and random distribution within rocks weighs against alternate possibilities for their origin. Discovering hematite in the rocks strengthens this conclusion. It also adds information that the water in the rocks when the spherules were forming carried iron, said Dr. Andrew Knoll, a science team member from Harvard University, Cambridge, Mass.

Mars' Moons

Earth has one moon; Mars has two: Phobos and Deimos. They don't look like our moon at all, because whereas our moon was formed along with Earth, Mars' moons are simply captured big rocks. They are probably pieces from the Asteroid Planet moon which broke up. This is concluded because of their carbonaceous content.

Phobos is closer to Mars (5800 miles) and orbits it quickly, once every 7.66 hours. Deimos is farther out (14,500 miles) and orbits more slowly, at 30.35 hours. As a quick comparison to our moon which orbits about every 29 days, it is 250,000 miles from the earth, so Mars' moons are very close to it in astronomical terms. Australia is over twice the distance from the United States as Phobos is from Mars.


Mars moons


Even these moons, as small as they are,have their own craters. On Phobos there is a crater large enough to be named, Stickney. You can see it more clearly in the photograph below.


The very dramatic hole in its side is not an impact crater. If this rock had been hit that hard by another object, it would have shattered. This is a hole made by electrical machining. Further evidence of this origin is in the striations along the side and the rows of pit chains along these striations, as well. (Impact striations radiate outward in all directions from the crater.)

Mars, like Venus, has no magnetic north or south pole, but the reason is different. Venus has not got the magnetic poles because it rotates so slowly. Mars, however, used to have them, but they are gone now. The magnetic poles have two causes that work together: the spinning of the core of the planet and the amount of radioactive heating in its interior. Mars is the second smallest planet, and, in part due to its position in the planetary lineup, also has the smallest core. Since the heavy elements are concentrated in the cores of the planets, this means Mars also had the least amount of radioactive decay going on. But it was there.

Now, consider something else: On the inside of Mars is Earth, which had the giant,world-wide flood when the waters outgased after the hits from the initial breakup of the Asteroid Planet. On the other side of Mars was the Asteroid Planet which did not survive its internal heating. Because Mars is little, it did survive its internal heating but the amount of material outgased in the form of both water and magma were enormous for its size. That outgasing, however, did relieve the heat and the pressure from the interior.This vastly reduced its magnetic field as the heat was carried away from the interior. There was no longer enough radioactive material left to heat the interior enough to produce a magnetic field, even though the core was still turning. Thus, when we see Mars' ionosphere, we do not see the polar cusps. They are gone now.

Mars ionosphere

The MPR is the 'magnetic pileup region,' which is dominated by ions from the planet itself. The MPB is the 'magnetic pileup boundary,' which is between the MPR and the plasma sheath. The PEB is photoelectron boundary, which is defined by the altitude which can be reached by ionospheric photo-electrons with energies below 50eV. This boundary defines the top end of the ionosphere and the dynamics of its location.

A Brief History of Mars

  1. Initial heating of the interior by rapid radioactive decay.
  2. The Late Heavy Bombardment (3.9-3.2 million atomic years ago) which formed the large impact basins in the North.
  3. The initial breakup of the asteroid planet (800-700 million atomic years ago) which gave rise to the Hellas and Argyre impacts.
  4. These impacts caused the antipodal Tharsis Uplift and Elysium Uplift and their fault systems.
  5. Water outpoured as a result, forming oceans in the North.
  6. The final breakup of the asteroid planet (255-250 million atomic years ago).
  7. As the mantle continued to heat, the Northern Basins dropped as magma was outpoured from the interior, vaporizing northern oceans, giving rise to high CO2 content in atmosphere.
  8.  Iron content in the magma, combining with ocean water, gives rise to the rusty dust which colors the planet today. 
  9. Asteroid moon explodes (70-65 million atomic years ago), resulting in a final series of impacts on Mars and the population of smaller craters.

Update, April 8, 2015 -- Mars rover Curiosity spots 'ice cream sandwich' rocks

September, 2015 -- Water on Mars?