Bacteria Colonists

If life ever existed on Mars, it likely has survived in cracks deep underground (like on Earth) where geothermal heat keeps water liquid. Bacteria scrounge high energy minerals or energetic geothermal chemicals to allow them to feed. This article will ignore such, and discuss bacteria which are added to the surface of Mars.

The first wide spread colonists will certainly be bacteria, which have a key role in Terraforming Mars.

What Bacteria Need To Live

Bacteria (especially Extremophiles), are many times more hardy than multicellular life. They can be frozen for thousands of years and remain viable. Bacteria spores can survive in vacuum and the radiation of space for millions of years. But for bacteria to grow they need liquid water and an energy source. Water can exist as a liquid a shallow distance under ground on Mars (and occasionally, for short periods on the surface). Warming the planet would add to the air pressure (see Terraforming), and the heat would make transient liquid water more common.

Bacteria do not need to live right on the surface. In Antarctica, bacteria (and more complex life) have been found living under semi-transparent stones. The stones protect the life from UV light, and the wind. A tiny micro-environment exists under the stone which is less harsh than the surface. A layer of ice can likewise protect bacteria from the harsh conditions on the surface. Imagine a dark rock with some ice on it. In bright sunlight the rock warms, melting a tiny layer of water, protected from the vacuum, radiation, and cold above. Bacteria grow for an hour a day, but when the rock is shadowed (or at night) the water freezes and the bacteria become dormant again.

Cyanobacteria (blue-green algae), can live under ice, if the ice is thin enough for light to reach them.

High energy compounds (such as perchlorate) are generated on Mars by UV light. Some bacteria can break these down, if water is available. Thus the toxic dust problem on Mars will gradually go away as Mars becomes warmer and wetter. (Also if more oxygen is produced, UV light will be blocked by an ozone layer, and perchlorate formation will be slowed or stopped.)

Other bacteria can feed on compounds in soil and dust.

Early Bacteria Colonists

The first bacteria which will spread widely are likely to anorexic bacteria which will produce methane (a greenhouse gas) and sulphur dioxide (a poisonous greenhouse gas). This will be the brown-smelly Mars period. We will wish to encourage cyanobactia and plants to make oxygen (to break up the sulphur dioxide and to make an ozone layer).

Methane generating bacteria would be encouraged since methane is a greenhouse gas.

Bacteria are used by early colonists (such as fungi and lichen) to help break up rocks and create soil.

As mentioned above, we will wish to introduce bacteria which can feed on perchlorate.

Bacteria which can fix nitrates in the regolith will help make nitrogen available to plants. These are key in building soils.

Bacteria can act as food sources for larger creatures (amoeba, slime molds, plankton, etc.), and thus set the stage for larger, more complex life forms. They also act as food sources for simpler creatures (viruses).

Bioengineered Bacteria

It is possible that bacteria would be bioengineered for specific purposes. For example, cyanobacteria which could produce oxygen and survive in high-salt, very cold, high radiation environments would speed their spread across Mars. However, this should be considered a bonus. Once life is well established, it will surely adapt to local conditions.