The earliest simulation studies were carried out by the Air Force, and the studies during the past 6 years have been supported by NASA. Recently, these studies have received less support or have been terminated in favor of critical studies on the effects of biologically important environmental extreme factors on Earth organisms. These critical studies permit establishing the extreme environmental factor parameters in which Earth life can grow or survive. These data will have valuable application to the consideration of life on any planet, to the design of life-detection instruments, to the sterilization of space vehicles, and to the problem of contamination of planets. Some exploratory experimental studies are in progress to study the capabilities of organisms to grow under the assumed conditions on Jupiter. These include studies at high pressure with liquid ammonia, methane, and other reducing compounds. Early experiments simulating Martian conditions using soil bacteria were carried out by Davis and Fulton ([ref.70]) at the Air Force School of Aviation Medicine, San Antonio, Tex. Mixed populations of soil bacteria were put in "Mars jars" with the following conditions: 65-mm Hg pressure, 1 percent water or less, nitrogen atmosphere, sandstone-lava soil, and a temperature day-night cycle of +25° to -25° C. The moisture was controlled by desiccating the soil and adding a given amount of water. Experiments, conducted up to 10 months, demonstrated that obligate aerobes died quickly. The anaerobes and sporeformers survived. Although a small increase in the total number of organisms indicated growth, the increases in the number of bacteria may have been due to breaking up clumps of dirt. Roberts and Irvine ([ref.71]) reported that, in a simulated Martian environment, colony counts of a sporeforming bacterium, _Bacillus cereus_, increased when 8 percent moisture was added. Moisture was considered more important than temperature or atmospheric gases inasmuch as a simulated Martian microenvironment containing 8 percent moisture permitted germination and growth of endospores of _Clostridium sporogenes_. Increases in colony counts of _Bacillus cereus_ appeared to be influenced by temperature cycling ([ref.72]). Table II.—_Survival and Growth of Organisms in Simulated Planetary (Martian) Environments_ ------------------------------------------------------------------ Species Survival, Moisture Temperature, months °C