IS LIFE bubbling onto the Martian surface in muddy squirts? The discovery of what could be mud volcanoes on the planet suggest it is possible, providing a new focus in the hunt for alien microbes.
Three plumes have recently been identified as sources of methane in Mars鈥檚 atmosphere (快猫短视频, 24 January, p 19). This has led to suggestions that the gas could have been produced by microbes living a few kilometres beneath the surface, where it could be warm enough for liquid water to persist.
This would be difficult to confirm as drilling that deep for samples on another planet is beyond current technology. Now it seems that nature may have done the hard work for us, bringing mud from deep within the planet to the surface via mud volcanoes.
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Using images from the spacecraft, Dorothy Oehler and Carlton Allen of NASA鈥檚 Johnson Space Center in Houston, Texas, identified dozens of mounds at a site in the northern plains of Mars that bear a striking resemblance to mud volcanoes on Earth. These form a of sediment with a central crater (see photo).
Further evidence comes from infrared images of the Martian mounds, which show that they cool down more quickly at night than rock should, suggesting they are made of a fine-grained sediment such as mud.
Together with David Baker of Brown University in Providence, Rhode Island, Allen and Oehler also took a fresh look at some possible mud volcanoes identified previously by other researchers, about 1000 kilometres further north. Using light spectra of the mounds recorded by the , they found hints of iron oxides, which form in the presence of liquid water. will be presented at the Lunar and Planetary Science Conference in The Woodlands, Texas, this month.
Jack Farmer of Arizona State University in Tempe agrees that the mounds could be mud volcanoes, but cautions that other processes, like the retreat of glaciers, can leave behind similar heaps of sediment. Nonetheless, studying the clay from mud volcanoes would be of great interest, he says. 鈥淐lays have the ability to sequester organic molecules, like ammonia and proteins,鈥� he says. 鈥淭hey might retain a memory of any organisms that were there.鈥�
