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Terraforming

May 11, 2012

Most fans of science fiction will be familiar with terraforming. As its name indicates, terraforming is an hypothetical process of modifying a planet to make it more like Earth. Nowadays, the object might be to make it better than Earth. Terraforming usually means just modifying a planet's atmosphere and temperature to allow Earth-like vegetation to take control in a Gaia-sort of way.

The intended first target for such an effort has always been Mars, which seems like the easiest challenge among the planets of our own Solar System.[1-4] The first order of business is to give Mars a little more heat, so that its stores of frozen carbon dioxide can increase the atmospheric pressure. Once a carbon dioxide greenhouse is set into motion, this process would be self-perpetuating.

Among methods proposed to heat Mars are blackening its surface to decrease its albedo; and asteroid impacts, which have a lot of kinetic energy. The asteroids could also contain essential compounds, such as water. It's estimated that if all the frozen carbon dioxide on Mars were sublimed into the atmosphere, the temperature of Mars would increase by about seventy degrees Celsius, which would be above the freezing point of water.[1]

There are greenhouse gases more potent than carbon monoxide that would speed this process. I've reviewed these in a recent article (The Methane Greenhouse, January 25, 2012) These are methane (possibly imported from Titan), ammonia, and fluorine compounds. As an extreme example, sulfur hexafluoride (SF6) has a greenhouse heating effect that's many thousands of times that of carbon dioxide. When atmospheric conditions are right, vegetation would be introduced to finish the terraforming process.

Terraformed Mars (Daein Ballard)A terraformed Mars.

(Illustration by
Daein Ballard (edited), via Wikimedia Commons).

Unlike the Genesis Project of the second Star Trek movie, The Wrath of Khan, all this would happen over an extended period, possibly tens of thousands, or hundreds of thousands, of years. In the end, there would still be some problems, since Mar's lack of a magnetic field would allow too much radiation to impinge upon the surface. Leaded underwear would be standard issue.

Since terraforming takes so much time and effort, you would think that it would be impossible to make a major impact on Earth's temperature in a short time. A recent research collaboration of scientists from many research institutions[5] shows that changing the average temperature of a portion of the Earth over a span of decades is actually not that difficult.

Parts of the US have had global warming offset by the simple process of having more particulates in the atmosphere, and clean-air rules are now reversing that effect.[6-8] The research is reported in a two-part paper in the journal, Atmospheric Chemistry and Physics.[7-8]

Particulate pollution over the Eastern United States during the late twentieth century created a cold patch that temporarily obscured the effects of global warming.[6] Particulate matter in the air caused cooling by reflecting sunlight back into space. Now that particulate pollution, especially sulfates from coal-fired power plants, has been controlled, the greenhouse warming in this region has begun to ramp up to the global trend. Sulfates were responsible for acid rain.[6] [6]

US surface temperature for the period 1930-1990NASA Goddard Institute for Space Studies Surface Temperature Analysis for the period 1930-1990.

(Image by Eric Leibensperger, used with permission.).

The effect was localized because particulates remain in the atmosphere for a short time, on the order of a week. Although global mean temperature rose about 0.8 °C from 1906 to 2005, temperatures in this eastern "warming hole" decreased 1 °C from 1930-1990. The atmospheric particulate matter in that region peaked in 1980, and it's now been reduced by half. As a consequence, the cooling effect that's been counteracting global warming is now just 0.3 °C.[6]

Loretta J. Mickley, a Senior Research Fellow in atmospheric chemistry at Harvard, and a coauthor of the study, says that the US data is a prelude to what might occur in China.[6]
"Something similar could happen in China, which is just beginning to tighten up its pollution standards... China could see significant climate change due to declining levels of particulate pollutants... No one is suggesting that we should stop improving air quality, but it's important to understand the consequences. Clearing the air could lead to regional warming."

Quantitatively, the researchers found that anthropogenic aerosols at their peak reduced ground heating power by two watts per square meter, most of this because of sulfates.[7] This caused a strong climate response by cooling the central and eastern US by 0.5 - 1.0 °C during 1970–1990. The strongest affect was on the maximum daytime temperatures in summer and autumn.[8] The bulk of the cooling has been taken out of the atmosphere, and an additional warming of just 0.1 °C is projected.[8]

The research was supported by the Electric Power Research Institute and the U.S. Environmental Protection Agency.[6]

References:

  1. Terraforming Mars, NASA Web Site.
  2. Martyn J. Fogg, Tom Meyer, Stephen Gillett and Robert Haynes, "Planetary Engineering Bibliography," NASA, November 1995.
  3. M.J. Fogg, Terraforming Information Pages.
  4. Exploring Space, Mars Terraforming Timeline, Should We Terraform Mars?, PBS Web Site.
  5. The institutions involved in this study were the School of Engineering and Applied Sciences, Harvard University (Cambridge, MA), the Jet Propulsion Laboratory, California Institute of Technology (Pasadena, CA), the Division of Chemistry and Chemical Engineering, California Institute of Technology (Pasadena, CA), the School of Earth & Atmospheric Sciences and School of Chemical & Biological Engineering, Georgia Institute of Technology (Atlanta, GA), the Department of Civil & Environmental Engineering and Department of Engineering & Public Policy, Carnegie Mellon University (Pittsburgh, PA), Argonne National Laboratory (Argonne, IL), the Electric Power Research Institute (Palo Alto, CA), and the NASA Goddard Institute for Space Studies (New York, NY).
  6. Caroline Perry, "'Warming hole' delayed climate change over eastern United States," Harvard School of Engineering and Applied Sciences Press Release, April 26, 2012.
  7. E. M. Leibensperger, L. J Mickley, D. J. Jacob, W.-T. Chen, J. H. Seinfeld, A. Nenes, P. J. Adams, D. G. Streets, N. Kumar and D. Rind,"Climatic effects of 1950–2050 changes in US anthropogenic aerosols – Part 1: Aerosol trends and radiative forcing," Atmos. Chem. Phys., vol. 12 (2012), pp. 3333-3348.
  8. E. M. Leibensperger, L. J Mickley, D. J. Jacob, W.-T. Chen, J. H. Seinfeld, A. Nenes, P. J. Adams, D. G. Streets, N. Kumar and D. Rind,"Climatic effects of 1950–2050 changes in US anthropogenic aerosols – Part 2: Climate response," Atmos. Chem. Phys., vol. 12 (2012), pp. 3349-3362.