|
Sci Tech
Microorganisms grow at low pressures
USING A unique device known as the Andromeda Chamber to simulate conditions found on Mars, University of Arkansas researchers discovered that certain microorganisms called methanogens could grow at low pressures. Their findings imply that life could have existed on the Red Planet. Associate professor of biological sciences Tim Kral presented the preliminary results at a bioastronomy conference in Australia.
Kral and his team first grew test tube cultures of various methanogens in a Mars soil stimulant called JSC Mars-1. Derived from altered volcanic ash, it approximates the composition, grain size, density, and magnetic properties of Martian soil.
The researchers exposed the cultures to an atmosphere that consisted only of hydrogen and carbon dioxide, the raw materials methanogens need to produce energy. They incubated the cultures at each methanogen's optimal growth temperature. Methanogens release methane as a waste product, so the researchers were able to measure their growth by analysing the amount of methane produced.
After growing three different methanogens on Mars soil stimulant, Kral moved on to the next step — simulating various Martian conditions in the Andromeda Chamber, a large stainless steel vacuum container.
The chamber, which was originally constructed for comet simulations, consists of an insulated compartment with heating and cooling elements. A sample container, approximately one metre on each side, can be lowered into the chamber, which contains various detection and monitoring instruments.
The researchers grew methanogenic cultures in bottles and froze them. They inverted the frozen cultures and placed them below the surface of the soil stimulant in the sample container, lowering it into the chamber. After sealing and evacuating the chamber, they replaced the atmosphere inside with an equal mixture of hydrogen and carbon dioxide at 500 millibars (about half the Earth's atmospheric pressure). Finally, they raised the temperature of the chamber to 35 {+0}C to ensure that the cultures melted into the soil stimulant.
So far, the Andromeda Chamber studies indicate low levels of methane production. This means that the organisms are metabolising under low pressures, a significant finding. Martian life would have to be able to survive at such pressures, since Mars' atmosphere is much less dense than Earth's.
Kral's work with methanogens got a significant boost from the discovery earlier this year of large quantities of frozen water below the surface of Mars. "With the recent successful missions to Mars (Pathfinder, Global Surveyor, Odyssey), and especially the discovery that there is probably a vast ocean of frozen water below the surface, there is a greater possibility that life may exist below the surface today."
Martian surface conditions include low pressure, low temperature, little water, and an atmosphere that contains large amounts of carbon dioxide with almost no oxygen. Assuming that hydrogen and some water are present under the surface, of Mars the basic requirements for methanogen growth are met on Mars. And even if hydrogen is not present, carbon monoxide is, and some methanogens can use this instead of hydrogen.
Printer friendly
page
Send this article to Friends by
E-Mail
Sci Tech
|
