by Christopher P. McKay
10-11 Oct 2000

from NASAAmes Website

recovered through WayBackMachine Website

 

Summary

Making Mars habitable is in many ways restoring it to the state we believe it had billions of years ago: a thick atmosphere, a warm surface with bodies of liquid water, and life.

 

The scientific discussions at the conference focused on two main areas:

  1. warming Mars so that liquid water is present on its surface once again

  2. understanding the potential for ecosystems to develop on Mars as it warms from its present cold dry state to a warmer wetter world.

Talks by McKay, Haberle, and Zent pointed out that we do not know if Mars has enough of CO2 , H2O, and N2 to build a biosphere.

 

Carbon dioxide may be trapped in the south polar cap (small amount), absorbed in the soil (larger amount) or in the form of carbonate (as yet undetected). Water may be held as ground ice in the polar region. Nitrogen, a key element, may be in the form of nitrates in the soil (possibly with the carbonates).

One interesting area of new work presented at the conference dealt with the use of super greenhouse gases in warming up Mars. On Earth super greenhouse gases (mostly CFCs) are warming our atmosphere and destroying the ozone layer: both undesirable effects. On Mars warming the atmosphere would be desirable but without adversely affecting ozone formation.

 

Talks by Marinova and Gerstell reported on new calculations of how super greenhouse gases could be used to warm Mars. To effectively cover the infrared window region of left by the CO2 and H2O greenhouse effect several super greenhouse gases, each at low (ppm or less) concentration are needed.

 

Marinova listed the desired properties of these gases: they should be easily made on Mars since transport from Earth would be impractical; they should be long lived -- stable against destruction by sunlight; they should be easily made on Mars; not contain chlorine or bromine which destroy ozone; and should be ultimately produced biologically.

 

Gerstell reported on a search for even more effective super greenhouse gases using quantum mechanical calculations. It is clear if the gases are designed to optimize their infrared greenhouse properties, then significant improvements can be expected. Warming Mars with super greenhouse gases is a real possibility.

 

Climate models of Mars reported by Lorenz, Carlstrom, Fogg, and Zubrin provided insight on how the environment of Mars would respond to warming.

The biology of Mars begins, as Friedmann pointed out, when conditions on Mars become comparable to conditions in the most Mars-like place on Earth: the dry valleys of Antarctica. Simple microbial ecosystems that live just under the surface of sandstones in these valleys (the cryptoendolithic microbial communities) would be the first possible natural martian ecosystem.

 

Presentations by Graham and Cockell showed how the biological development on Mars would be in many ways analogous to mountain and polar biological succession on Earth. One can imagine how Mars would develop biologically by imagining a descent down a tropical mountain. In terms of biology, the key question is the availability of nitrogen.

 

In the paper by McKay, it was suggested that to recreate a biosphere on Mars there must be nitrogen present in the soil as nitrate or genetic engineering of microorganisms allowing them to take in gaseous nitrogen at present martian levels.

In papers by Navarro and Heath the importance of trees as biological engines of change was emphasized. Trees create much more biomass and produce much more oxygen than microbial ecosystems. Navarro suggested that understanding when the first tree can grow on Mars is analogous to understanding what sets treeline on tropical mountains. The highest treeline in the world occurs on Pico de Orizaba in Mexico and this is under current intensive study.

New work on the survival and functioning of insects under low pressures was presented by Cockell. His results indicate that many insects can function at pressures as low as 20 times less than sea level pressure on Earth (Mars today is 120 times less).

 

He concluded that plants and insects could be introduced on Mars together.

Mars is too small to have plate tectonics but Boston suggested that biological cycling should be developed to recycle nutrients. Key points include imagining the main repositories of carbon to be the living biomass and atmosphere as it is in both the tropical forests and in the root zones of alpine and arctic tundras rather than in soils as in the temperate zone.

 

Primary workhorses of biocycling could be microbial communities introduced into the deep and near Martian subsurface to perform return of materials back to the surface from buried sediments, a process dubbed "bioinjection".

Genetic engineering offers many possibilities for bringing life to Mars and in papers by Hiscox and Boston these possibilities as well as the limitations of genetic engineering were discussed.

 

Both authors agreed that there is great value in directed selection of whole organisms in addition to genetic engineering techniques, that is, the exposure of microbes and plants to conditions ever more closely approximating those to be found on Mars to "mine" for novel traits that may arise in response to those conditions.

Boston focused on specific areas of improvement of the future carbon cycle on Mars including improvement in photosynthetic enzymes, the development of ultraviolet photosynthesis, accommodation to low light levels, homeostatic mechanisms in plants that could be expanded, generation of protective coatings by plants, photosynthetic symbionts of animals and the use of unique capabilities found in Earth's alpine and arctic plants.

In the wrap up session McKay suggested that doing a near term experiment with a plant growth module on a Mars lander was an important first step to bringing life to Mars and Mars to life.

 

Korycansky discussed more speculative approaches to bringing outer solar system objects to Mars as a source of water and nitrogen. Finally McKay, Robinson and Zubrin opened a brief discussion of the societal and environmental issues raised by the idea of terraforming Mars.

 

These topics are to be the focus of a future conference.