Space Facts

Planet Mars

The Red Planet

This picture was taken by Mars Global Surveyor Mars Orbiter Camera of the Elysium highlands and Mare Cimmerium regions, March 28, 2006. Season: Northern Spring/Southern Autumn. Image Credit: NASA/JPL/Malin Space Science Systems

Mars is planet number four of the Solar system. Named for the Roman god of war (similar to the Greek god Ares), but was originally a god of fertility and vegetation. The function of the god seemed to change as Romans went from an agrarian society to a more militaristic one. Why the association? The color of Mars in the night sky is slightly reddish or pink in hue. Red is, after all, the color of blood.

The planet Mars is only about half the diameter of Earth and has a much thinner atmosphere than our home world. The surface gravity is only about 38% that of Earth. This is virtually identical to that of Mercury, but Mars is much more capable of retaining an atmosphere because it is so much farther from the sun. Mars has two moons, Phobos and Deimos, which are thought to be captured asteroids.

Size comparison of terrestrial planets with the Moon (left to right): Mercury, Venus, Earth, Luna and Mars.		The first four planets of the Solar system are called "terrestrials" because of their rough similarity to Earth. The other type of planet is called "gas giant," because the bulk of each such planet is gaseous. The Solar System Facts table gives more comparisons between the planets.

Could Planet Mars Ever Sustain Life?

Mars has no oceans, but what if that could be changed? What would it take to terraform (make like Earth) the planet Mars?

More Air for Planet Mars

Of course, colonizing the red planet doesn't need anything as fancy as terraforming. There are many ideas how men and women can live off the land, mining water from sub-surface ground ice, and growing their own food. Living in pressurized huts can be cozy, but potentially dangerous. Radiation from solar storms can be deadly, but if the living quarters can be underground or cut into the sides of hills, this hazard can be minimized. Meteors can also pose a deadly hazard. The extremely thin atmosphere offers poor resistance to all but the tiniest meteors.

If planet Mars can be improved with a thicker atmosphere, several advantages are achieved:

• Defense against most smaller meteors
• Improvements in warmth retention so the nights might not be so cold
• Improved defense against solar radiation
• No more depressurization hazards
• And the possibility of a breathable atmosphere

One major drawback with adding a thicker atmosphere is the increased dust storms. High silica content could make breathing Martian air even more deadly than the earlier hazards. Such a problem could be handled by adding oceans, but a few concerns need to be addressed before making planet Mars so wet.

Can planet Mars retain the additional atmosphere for an acceptable length of time? Even Earth is losing atmosphere to the depths of space. Sunlight hitting the upper atmosphere excites some of the atoms enough to exceed escape velocity, and some of those are headed in the right direction for that escape. Mars, thankfully, is farther from the sun, so the sunlight problem is reduced, but Mars is a smaller planet with weaker gravity less capable of holding onto its atmosphere. It seems gravity is not the main problem. Mars lacks a strong magnetic field. Earth has one and it protects Earth's atmosphere from the ravages of the solar wind. This magnetic umbrella extends out from Earth approximately 50,000 kilometers (~31,000 miles). At planet Mars, the solar wind has direct access to the planet's atmosphere, effectively blowing it away. The rate is slow, but over the last 4 billion years, Mars apparently lost an atmosphere as thick as that on Earth. Without an active system of volcanism, what was lost was not replaced.

So, what if an atmosphere could be added to Mars? If it took 4 billion years to lose its atmosphere, one as thick as Earth's could easily last a million years. In fact, enough of it might last 100 million years before a recharge would be needed. That, however, is a big "if." Most of the Martian atmosphere may have been lost in a much shorter period of time and merely stabilized at its current level, with much of the atmosphere frozen out at the poles — alternating between North and South as the Martian seasons change.

Okay, let us assume for the moment that a beefed up atmosphere on planet Mars could last even a hundred thousand years before a recharge would be needed. That's twenty times the length of human history. That would be worth something. How would we get the extra air for Mars? One way might involve herding comets to crash into Mars. But careful there! One miscalculation could result in hitting the wrong planet. Six billion voices would be very angry at that.

That would be using conventional technology, but that would be very expensive and very time consuming. Sending one rocket out beyond Pluto with enough fuel to steer one comet all the way back to hit planet Mars would be a major undertaking rivalling the Apollo program that sent men to the Moon. But we would have to do it dozens of times! Such a program would also require finding comets of the right chemical composition. Comets typically contain such things as water ice, and frozen gases such as carbon dioxide, carbon monoxide, ammonia and methane, but occasionally contain more exotic compounds like hydrogen cyanide, formaldehyde, ethanol and methanol, and perhaps more complex molecules such as long-chain hydrocarbons and amino acids.

An Ocean for Planet Mars, too?

Modified map of Mars showing what it might look like with oceans.

If someday a technological breakthrough helps us understand and conquer the fabric of space itself — perhaps like Star Trek's "warp drive" — we might find it possible to lift large quantities of the appropriate gases from Jupiter in minutes instead of the months or years involved with comets. A similar technique could be used to build the Martian oceans, though this secondary task could easily take more than a hundred times as long because of the greater mass and bulk involved.

Oceans pose a new problem, but come with many benefits. There is a very real danger that the oceans could freeze over. Ice is highly reflective and that could forever lock planet Mars in the proverbial ice box. The worst thing that could happen in our experiment is for the red planet to become white. And after all, Mars is farther from the sun and thus cooler, everything else being equal.

All that water, however, tends to be self-regulating. If temperatures drop, there will be less evaporation and thus fewer clouds and less rain (or snow). Clouds make things cooler because they are white and reflective. Clouds help to keep Earth cooler than it would otherwise be, reflecting light (and heat) back into space. And of course, snow and ice help to keep things cooler with their reflectivity.

Large bodies of water tend to stabilize temperatures between night and day. The diurnal temperature swings in Earth's deserts, for instance, can be from 50 °C during the day to below 0 °C (freezing) in the early morning hours just before sunrise (that's 122 °F to below 32 °F, a better than 90 °F daily swing). Along Earth's coastline, however, such temperature swings are virtually unheard of.

Large oceans have the additional benefit of cleaning the air. With the heat of sunlight, water evaporates, and water vapor in the air could perform a cleanup job, condensing and clearing the atmosphere of deadly high-silica dust.

There needs to be sufficient ocean cover to prevent large areas from accumulating ice and snow. Allowing ocean currents access to the polar regions may be critical for such a project to work. For this, there is no problem in the North, which has a lower average elevation than the southern hemisphere. Warm equatorial waters from say the Hellas Sea (the large, dark blue spot in the lower right of the above map) could keep the south pole from becoming dangeously icebound. Deep oceans absorb more light than shallow, coastal waters. Shallow water should be kept at a minimum for the sake of the planet's heat budget.

Once the materials are in place (the additional atmosphere and oceans), planet Mars would need to remain dark enough in color to absorb sufficient light (converting it to heat) to keep the planet from suffering runaway frostbite. If our experiment fails, then we could have one very large winter resort — lots of ice, but never again any snow.

Terraform planet Mars? It could pose many challenges unlike anything humanity has ever tackled, but it might just be worth it. Imagine a sister world in our own Solar system with cities and industry — an active trading partner with Earth. Just imagine!

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