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Hot Topic Solar System Mars Build Your Own Planet
Build Your Own Planet
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Posted:   12/20/02

Summary: Build your own virtual planet, complete with weather, habitable tropics and a tunable thermostat. In reality, changing an entire biosphere would dwarf the limits of engineers' most grand projects: Hoover Dam, Suez and Panama Canals, or hurricane cloud-seeding.

Build Your Own Planet

There are two classes of outcomes in any attempt to terraform, or modify the ecosystem of an entire planet: red--meaning a dry, rocky, airless sphere; or green-meaning a semi-lush, oceanic, breathable biosphere.

The Astrobiology Magazine staff conducts daily simulations on a mock planet, as different parameters are fed into various visualizations of cloud cover, continents and oceans. Visit or bookmark the updated content.

The wide angle view of the Martian north polar cap was acquired on March 13, 1999, during early northern summer. The light-toned surfaces are residual water ice that remains through the summer season. The nearly circular band of dark material surrounding the cap consists mainly of sand dunes formed and shaped by wind. The north polar cap is roughly 1100 kilometers (680 miles) across.Credit: NASA/JPL/Malin Space Science Systems

Mars Future?

Based on the world climate models of McKay, Zubrin,and Fogg, this online planet simulation allows addition of greenhouse gases like water vapor, ammonia, carbon dioxide and perfluorocarbons to Mars. In addition for different amounts of heat retention and reflection, the albedo and insolation can be adjusted.

Since Mars has stored greenhouse gases (carbon dioxide) both at the polar caps and in the surface rocks and soil (regolith), those outgassing reservoirs can be freed up with warming and climate forcing.

The calculation is based on a one-dimensional (1D) climate model, and does not account for time-dependent processes. For habitable zones to develop at a particular latitude--either polar or equatorial-- the temperature must rise above water freezing (0 C). The Martian pressures shown currently are about 1% of Earth's atmosphere (~1 bar).

Some intriguing features of this model include:

  • a dense carbon dioxide layer is not necessary (>1000 millibar). Indeed it is difficult to find a parameter set that can achieve such a thick Martian atmosphere.
  • small additions of perfluorocarbons (>1 microbar CFCs) however can achieve high latitude and polar temperatures above freezing. McKay, et al estimate "the required times scale for [halocarbon] climate and atmosphere modification is on the order of 50 years".
  • positive feedback from outgassing as the planet warms, which frees up more greenhouse gases, can reduce the requirements of terraforming by as much as two orders of magnitude (100x) compared to a planet without a reservoir of trapped gases in the soil and rocks

  • controlling an equilibrium condition is dependent on artificially heating the planet (Tdelta) with some active climate forcing. This is likely a better engineering bet than allowing a runaway greenhouse effect to take hold of a planet's meteorological future. By varying the insolation (S) by 10% (S=1.1), one can show the effects of how orbitting mirror might focus more sunlight onto Mars.

    Mars Past

    The terraforming simulation also can provide a simple model of the Martian past, when once wet and possibly warm conditions were created by a thicker carbon dioxide atmosphere than today. Many scientists believe that carbonate rocks (regolith) absorbed (or fixed) this atmosphere. Without this blanket of greenhouse gases to trap incoming solar radiation, the planet cooled dramatically, and more carbon dioxide froze at the poles. This primitive Mars can be approximated by adding 300 to 600 millibars of carbon dioxide P CO2 back to the atmosphere.

    Melting dry ice from the entire southern polar cap is predicted to give Mars an atmosphere on the order of 50 to 100 millibar (or 5-10 % of the Earth's atmosphere). Once the temperature rises by 4-20 degrees, the trapped soil gases could supplement this atmosphere to around 300 millibars (30 % of the Earth's atmosphere).

    What's Next

    While the atmospheric physics of warming a planet may be simplified, the practical engineering is still daunting. So far, three main proposals have focused on: 1) heating up frozen carbon dioxide with polar mirrors; 2) importing comets and asteroids rich in trapped greenhouse gases like ammonia or methane in orchestrated collisions; 3) perfluorocarbon factories to release perhaps the most powerful greenhouse gas, CFC.

    The scale of rocket transport for such large masses however remains a key limit. But the basic Martian ingredients for plant life are available and perhaps self-sustaining once at least tropical latitudes elevate about the water freezing temperature. The three reservoirs of carbon dioxide on Mars - the atmosphere, the dry ice in the polar caps, and gas adsorbed in the soil - provide a positive feedback, since warming will outgas or melt this greenhouse gas, thickening the atmosphere further to trap more sunlight and thus dramatically accelerating Martian habitability.

    Related Web Pages

  • Daily Terraforming Simulations Astrobiology Magazine
  • Mars Scout
  • Mars Exploration Program
  • Mars by Stories
  • Impact Crater Landing Sites for the 2003 Mars Exploration Rovers
  • Mars Exploration Rover Homepage
  • 2003 Mars Exploration Rover Mission
  • Smoking Craters?
  • Water on Mars

  • Variables shown in red are the primary climate forcing factors: light-dark albedo, incoming solar radiation, or greenhouse gases (particularly perfluorocarbons and methane).

    Pressure units (1 bar ~ 1 atm)
    Millibar (mbar) x 100 = Pascals (Pa)
    Pascals (Pa) x 0.01 = Millibar (mbar)
    Millibar (mbar) x 0.0145 = Pounds-force per square inch (psi; Ibf/in2; Ib/in2)
    Pounds-force per square inch (psi; Ibf/in2; Ib/in2) x 68.947 = Millibar (mbar)
    Millibar (mbar) x 0.75 = Millimetres of mercury (mmHg)
    Millimetres of mercury (mmHg) x 1.333 = Millibar (mbar)
    Millibar (mbar) x 0.401 = Inches of water (inH2O)
    Inches of water (inH2O) x 2.491 Millibar (mbar)

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