Can Humans Use Martian Water?

Teacher's Notes

No oceans, lakes, or rivers. Where's the water? Transparency Master

As seen from space Mars has no water on its surface whatsoever. Even if water were present it would be frozen solid due to the very cold temperatures on Mars' surface. The polar caps of Mars may hold significant amounts of water, but most of the ice in the polar caps is frozen carbon dioxide. There is speculation that astronauts may be able to get water from deep under that Martian soil where it forms a permafrost layer. If water is available on Mars, it may be contaminated with dissolved minerals making it salty like sea water and unsuitable for humans. Several methods may be used to purify water. Mechanical filters and diffusion filers work well, but they would have to carried to Mars with the explorers.

Things to Emphasize

1. Water is recycled in the environment.
2. Water will dissolve many substances. Many of these substances will cause the water to become unsuitable for living things.
3. Plants have the ability to use slightly "polluted" water, and release it into the air as "pure" water (vapour). Reclaiming this water vapour may by a simple method by which pure water may be obtained on Mars.
4. Science investigation involves a multi-step inquiry process: ask an initial question, plan the investigation, record observations and collect data, analyse data to draw a conclusion, and communicate the findings.

Investigation

Here is a very dramatic demonstration of the effects of adding contaminants to water.

Observation Chart Master

Water Condition	Growing Plant	Germinating Seeds	Instructions
Tap Water			Water daily using ordinary tap water.
Salt Water			Water daily using ordinary tap water with rock salt added, using about one handful per litre of water.
Acidic Water			Water daily using ordinary tap water, with an equal amount of vinegar.
Alkaline (Basic) Water			Water daily using ordinary tap water to which has been added a capful of ammonia cleaning liquid per litre of water .

Explanation

A plant's ability to absorb water arises whenever the concentration of a dissolved substance inside a cell becomes larger than the concentration outside the cell. ONLY THE WATER MOLECULES MOVE INTO THE CELL. If the dissolved substance outside the cell is too large, water moves out of the cell (by a process called osmosis) and the cell dies.

Topics for class discussion

1. Everyone knows that chemical lawn fertilizer is good for lawns. Why do the manufacturers of chemical lawn fertilizer warn you to avoid putting too much fertilizer on the lawn?

2. Why is it important to dispose of chemicals safely, and not allow them to be dumped where they might end up in rivers, streams, lakes, or drinking water?

3. If the frozen water found on Mars is too salty for plants or animals, how might the astronauts purity the water?