* Astronomy

A leading international space scientist says there is now clear evidence of life on Mars but that American authorities are hesitating from announcing it for political reasons.

"The discovery of liquid water on Mars combined with earlier discoveries of organic substances in a meteorite that came from Mars, and also of methane in the Martian atmosphere all point to the existence of life -- contemporary life -- on the Red Planet" - Chandra Wickramasinghe, a globally renowned astrobiologist.

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In a quest to understand the source of methane detected in the atmosphere of Mars, NASA scientists are looking at methane bubbling from the ground at an outdoor salt factory on Mexicos Baja Peninsula. By measuring carbon isotopes in the Mexican methane, these scientists hope to help unravel the mystery of the martian methane. In particular, they want to know whether or not the martian methane, like most methane on Earth, is made by microbes.

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-- Edited by Blobrana at 13:50, 2008-06-09

Title: The Potential for Lithoautotrophic Life on Mars: Application to Shallow Interfacial Water Environments
Authors: Steven M. Jepsen, John C. Priscu, Robert E. Grimm, Mark A. Bullock

We developed a numerical model to assess the lithoautotrophic habitability of Mars based on metabolic energy, nutrients, water availability, and temperature. Available metabolic energy and nutrient sources were based on a laboratory-produced Mars-analogue inorganic chemistry. For this specific reference chemistry, the most efficient lithoautotrophic microorganisms would use Fe2+ as a primary metabolic electron donor and NO3- or gaseous O2 as a terminal electron acceptor. In a closed model system, biomass production was limited by the electron donor Fe2+ and metabolically required P, and typically amounted to ~800 pg of dry biomass/ml (~8,500 cells/ml). Continued growth requires propagation of microbes to new fecund environments, delivery of fresh pore fluid, or continued reaction with the host material. Within the shallow cryospherewhere oxygen can be accessed by microbes and microbes can be accessed by explorationlithoautotrophs can function within as little as three monolayers of interfacial water formed either by adsorption from the atmosphere or in regions of ice stability where temperatures are within some tens of degrees of the ice melting point. For the selected reference host material (shergottite analogue) and associated inorganic fluid chemistry, complete local reaction of the host material potentially yields a time-integrated biomass of ~0.1 mg of dry biomass/g of host material (~10^9 cells/g). Biomass could also be sustained where solutes can be delivered by advection (cryosuction) or diffusion in interfacial water; however, both of these processes are relatively inefficient. Lithoautotrophs in near-surface thin films of water, therefore, would optimise their metabolism by deriving energy and nutrients locally. Although the selected chemistry and associated model output indicate that lithoautotrophic microbial biomass could accrue within shallow interfacial water on Mars, it is likely that these organisms would spend long periods in maintenance or survival modes, with instantaneous biomass comparable to or less than that observed in extreme environments on Earth.

Source: Mary Ann Liebert Inc.

Elysium's frozen sea on Mars is one of the most promising places to look for life on the Red Planet, scientists say.
But planned missions designed to search for microbes below the Martian surface will not drill deep enough to find living cells, the UK team has said.
Researchers at University College London say that microbes in the first couple of metres of Martian soil would be killed off by intense radiation.
Life might survive deeper down, where conditions are more benign.

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