Activity 1: Selecting Plants for Space Travel

The dry-mass to water ratio of plants will be an important consideration for the selection of plants that we will grow in Lunar or Martian greenhouses. Plants can be watered with recycled "gray water", but the food that the plants produce will provide an important source of consumable water.

Procedure

  1. Examine the Chart of Various Crops (see Resources section of this unit).  Rank order the crops according to each of the columns from B – I (excluding J).  What is the significance of each of these components related to the crops identified?
  2. Divide the class into groups and have the groups choose from the vegetables and fruit identified in the Characteristics of Various Crops chart.
  3. Determine the mass of each sample when it is fresh (in grams). We'll let mB represent the mass before dehydration.
  4. Dehydrate the sample by placing it in a warm oven at about 80°C to 90°C or in a household dehydrator (the kind used for preserving food) until the item is thoroughly dehydrated.
  5. Cool the sample and re-measure its mass (in grams). Similarly, we'll let mA represent the mass after dehydration
  6. Calculate the ratio (mB - mA)/mA. This is the water to solid (W-S ratio) ratio for the food item.

Analysis

  1. Create a graph plotting the water to solid ratio (W-S ratio) as a function of the item's storage time. Examine the graph to determine if there is a relationship between the W-S ratio and the storage time.
  2. Create a graph plotting the water to solid ratio (W-S ratio) as a function of energy content. Examine the graph to determine if there is a relationship between the W-S ratio and the energy content.
  3. Based on the analysis of these graphs (and considering the crop yields given in the chart Characteristics of Various Crops which follows in the Resources section) which crops would be best suited to providing a source of consumable water?