Twenty-six bacteria typically recovered from spacecraft were examined by researchers to see if they could grow under low pressure, temperature and oxygen conditions like those found on Mars. Plate A shows the control group grown under standard Earth pressure (1013 millibars) and oxygen and at 86 degrees Fahrenheit. Plate B shows the bacteria that can survive when temperature is dropped to freezing. Plate C shows the bacteria that survived with freezing temperature and no oxygen. Plate D shows bacterial growth at pressure as low as that on Mars (7 millibars), no oxygen and freezing temperature. Only one bacterium, Serratia liquefaciens, survived the harsh conditions. Arrows indicate locations of Serratia liquefaciens. Credit: Schuerger et al./University of Florida