Mars2

Mars
by Bob Perry 2008

Some Comments on Mars

The Earth is too small a basket for all the eggs of the human race. In the foreseeable future, mankind will become a space faring species. We will establish our biosphere on the moon and Mars and build space habitats and manufacturies using lunar, Martian, asteroid and comet resources and solar power. The inside-out world of space habitats will be discussed elsewhere. Here, let's talk about "worlds". Earth will remain our home world, "world" being a key word, because we are planetary chauvinists. Mars is at the cold edge of our sun's habitable zone and it has a few other flaws preventing it from being a second home.

1) Mars needs more atmosphere

2) Mars needs more water.

3) Mars needs a magnetic field

Mars has clear signs of having had flowing water - obvious erosion. (click for fullsized image)

But the Martian atmospheric pressure is much too low now for water to exist as a liquid. Water on Mars does the same thing as carbon dioxide on Earth, it sublimes.

So, for liquid water and hence, our entire biosphere, to exist on Mars, first the atmospheric pressure must be increased and second, Mars must be warmed. That is to say, Mars should be teraformed.

Mars was once all wet. Detectable deuterium and hydrogen in the atmosphere are in ratios different than Earth's. Mars has proportionately more deuterium. The conclusion: Mars has lost hydrogen. The simplest explanation is that UV light from the sun can break apart water molecules and, with the ions having a range of velocities due to their average temperature, a small percentage of the hydrogen will be moving at or above escape velocity. After all, Mars has only one third the gravity of Earth. Deuterium is twice as massive as hydrogen and oxygen sixteen times as massive, so they will have less velocity than hydrogen and be less likely to escape. Estimating how much water is in Mars's polar caps and how much hydrogen Mars has lost, the writers at WetMars conclude that early Mars had enough water to have had a global ocean 100 feet (about 30 meters) deep.

For Mars to have had liquid water in the past, its atmosphere must have been warmer and much denser. The heavier ions and molecules must have been lost by another process. The most likely loss mechanism is erosion by the solar wind. Quote: Lacking a planet-wide magnetic field, most of the Red Planet is exposed to the full force of the incoming solar wind. "The Martian atmosphere extends hundreds of kilometers above the surface where it's ionized by solar ultraviolet radiation," says Dave Mitchell, a space scientist at the University of California at Berkeley. "The magnetized solar wind simply picks up these ions and sweeps them away. In 1989 the Soviet Phobos probe made direct measurements of the atmospheric erosion," he continued. When the spacecraft passed through the solar wind wake behind Mars, onboard instruments detected ions that had been stripped from Mars's atmosphere and were flowing downstream with the solar wind. "If we extrapolate those measurements 4 billion years backwards in time, solar wind erosion can account for most of the planet's lost atmosphere."

Here on Earth we're protected from the solar wind by a global magnetic field (the same one that causes compass needles to point north). Our planet's magnetosphere, which extends far out into space, deflects solar wind ions before they penetrate to the atmosphere below. http://science.nasa.gov/headlines/y2001/ast31jan_1.htm

The remaining atmospheric loss could have been caused by energetic impacts by large asteroids or comets. An event in the range of a billion megatons of TNT would certainly do something besides make a large crater. The Chicxulub impact on Earth 65 million years ago was about that magnitude. It probably wiped out the dinosaurs and may have blasted away some of Earth's atmosphere. http://space.newscientist.com/channel/solar-system/comets-asteroids/mg15921518.900 And, after all, Mars is on the edge of the asteroid belt so it gets more impacts.

In summary, we want Mars to be our second planet, our second home world. We will capture comets and gently export the water and other valuable chemicals including nitrogen and oxygen to Mars, and since Mars needs a magnetosphere, we will build power plants and a globe encircling power cable carrying enough current to create one.