Making Sense Of Mars MethaneMaking Sense Of Mars Methane
By David Tenenbaum In particular, they want to know whether or not the martian methane, like most methane on Earth, is made by microbes. The 2003-2004 observations of methane on Mars (ranging from 7 to 200 parts per billion) were made remotely by three teams working with separate data, and their accuracy is still under debate, says Brad Bebout, a microbiologist at NASA's Ames Research Center. But if the methane is truly present in the atmosphere of Mars, then something must be producing it on the planet now, because the gas is broken down by sunlight within 300 years.Most methane in Earth's atmosphere is made by primitive microbes called archaea that reside in anaerobic locations like rice paddies and the guts of ruminants like cows. However, methane is also produced non-biogenically, by reactions between water and hot, carbon-bearing rocks, or by the natural decay of coal and petroleum.Methane, composed of one carbon and four hydrogen atoms, attracts a lot of attention from astrobiologists "because it is a key biomarker," says Bebout. "But methane can be produced by non-biological means, so when you see it in the atmosphere of a planet, biology was not necessarily involved, and that's why we want to know about isotopes." Isotopes are key to understanding the origin of methane because organisms tend to use more of the lighter isotopes. Biogenic methane usually - but not always - contains a higher percentage of the lighter carbon-12 than non-biogenic methane, which contains relatively more of the heavier carbon-13. The two types of carbon atoms both have the same number of protons, but carbon-13 has one more neutron than carbon-12. Isotopic measurements of the carbon in martian methane are a goal of the tunable laser spectrometer on NASA's Mars Science Laboratory, a rover now scheduled for launch in Fall 2009. But to get context for interpreting that data, scientists want more information on how primitive life produces methane on Earth, and one of the best locations for that is the salt factory on Baja. The salt flats of Guerrero Negro (the name, "black warrior," is taken from a nearby shipwreck) are an excellent outdoor laboratory because pools of increasing salinity are created as ocean water is evaporated to concentrate the salt. In many of the pools, microbial mats dominated by salt-tolerant cyanobacteria generate small amounts of methane, which is made by archaea living in association with the photosynthetic cyanobacteria. Bebout has identified these archaea, and is working on measuring their individual contributions to the overall level of methane.This microbial mat is absent in the hyper-saline Area 9, where methane is even more abundant: a stream of gas containing about 50 percent methane is bubbling up to the salty surface. "In that area, there is no mat; the bottom is basically solid gypsum," says Bebout. Apparently that gypsum is home to some archaea, because the carbon isotopes suggest that the methane bubbles have a biological origin. The isotopes, however, are not conclusive, because they are slightly outside the accepted range for biogenic methane. In cases like these, scientists can try to clarify the methane's origin by looking not only at its carbon atoms, but also at its hydrogen atoms. Hydrogen has two stable (non-radioactive) isotopes: protium (containing one proton and no neutrons) and deuterium (one proton plus one neutron). The combined isotopes of the hydrogen and carbon in the Area 9 methane are in a range "that is usually not considered biological," says Bebout. However, when the geologic conditions are taken into account, "It's very unlikely this is caused by water-rock interactions, or is thermogenic - resulting from the decay of organic matter - so we are pretty sure it is biological." Carbon and hydrogen isotopes in the Area 9 methane comprise "a pretty unique signature," which falls outside the accepted range of biogenic methane, and thus begs for a more complete explanation, says isotope expert Jeff Chanton, a professor of oceanography at Florida State University. For that reason alone, the salt ponds in Baja are worth studying.The primitive bacteria that are making methane in Area 9 may resemble whatever is making methane on Mars, says Chanton. "If there was life on Mars, it would not be like little green men. It would be some sort of microbe, a prokaryote [a cell without a nucleus]. On Earth, bacteria were the first form of life." Finding evidence of ancient bacteria on Mars would not be too surprising, considering that early Mars was warm and wet, rather like Earth during the evolution of methane-making bacteria. A better understanding of methanogens in the salt flat and further isotopic study of their methane will help interpret future measurements of the isotopic composition of methane on Mars. The recent detection of highly saline environments on Mars by Mikki Osterloo, of the University of Hawaii, using data from the THEMIS instrument on NASA's Mars Odyssey orbiter makes the saline investigation all the more important, Bebout says. "We want to really go through the system and characterize all of these environments, which might be like something the MSL rover would stumble on, and figure out what's going on. On Earth, we can do experiments we can't do on the rover." Bebout's research is supported by a grant from NASA's Exobiology and Evolutionary Biology program. - 11/6/2008 - Comment {0} - Post CommentProbe again fails to obtain Martian soil sampleProbe again fails to obtain Martian soil sample
by Staff Writers "Virtually none of the material made it down into the oven" after the probe dug up new soil clumps from the Martian permafrost with its robotic arm, William Boynton, an investigator for Phoenix's thermal and evolved gas analyzer (TEGA), said during a press teleconference Monday. "We ran a vibrator to help move the soil, we ran it at a higher frequency... (but) we found out today that did not work," Boynton said. It was a further setback for Phoenix, whose TEGA analyzer at the weekend was not able to obtain smaller, testable bits from the Martian landscape which researchers hope will provide clues to whether the planet was once habitable for microbial life. Between 20 and 30 milligrams of soil is necessary for analysis, but Boynton said less than one milligram of matter passed through the screen into one of the probe's test facilities. The screen is designed to allow through it particles measuring one millimeter (0.04 inch) or less. Inside the port there is an infrared beam which determines if particles enter the machine. Once it gets a sample, the TEGA instrument spends several days analysing its content, first testing for the level of water content, and then heating it gradually to 1,000 degrees Celsius (1,832 Fahrenheit) to better assess the mineral composition. Phoenix, which landed on the stark terrain of Mars' north pole region on May 25, collected the first sample on Thursday. The team aims to try the procedure anew in the coming days. Should that fail, mission scientist Doug Ming said, they will attempt a "sprinkle test" in an attempt to jar smaller soil pieces free. "We hope to deliver a sample in about two sols," or Martian days, Ming said. Boynton, who is a scientist at the University of Arizona which is coordinating significant elements of the mission, said the team was not urgently pressed for time. "It will be at least a week or two (of failure) before we start to get terribly concerned," he said. Phoenix has a total of eight "ovens" that can be used to test separate samples from the Martian surface. If need be the team can also employ an alternate delivery mechanism which would grind up the sample. "So we are still pretty optimistic that one of these techniques will work for us," Boynton said. Phoenix is on a three-month mission to inspect Mars' soil for the right combination of water in its ice form and minerals that would demonstrate the planet could or can support basic microbial life. - 11/6/2008 - Comment {0} - Post CommentNASA Lander Will Sprinkle Martian Soil For Microscope To ViewNASA Lander Will Sprinkle Martian Soil For Microscope To View
Tucson AZ (SPX) Jun 11, 2008 The team operating NASA's Phoenix Mars Lander plans to instruct the spacecraft in the next few days to use its Robotic Arm to sprinkle a spoonful of Martian soil onto a wheel that will rotate the sample into place for viewing by the spacecraft's Optical Microscope. Meanwhile, commands for Phoenix's activities today are to continue a set of atmosphere observations begun during the Martian evening earlier Tuesday in coordination with overhead passes of NASA's Mars Reconnaissance Orbiter. These take advantage of opportunities for instruments on Phoenix and on the orbiter to examine the same column of atmosphere simultaneously from above and below. "It allows us to put the Phoenix measurements into global perspective and gives a ground level calibration for the orbiter's measurements," said Phoenix Project Scientist Leslie Tamppari of NASA's Jet Propulsion Laboratory, Pasadena, Calif. On Monday, Phoenix tested delivering Martian soil by sprinkling it rather than dumping it. The positive result prompted researchers not only to proceed with plans for delivery to the microscope, but also to plan on sprinkling a sample in the near future into one of the eight ovens of an instrument that bakes and sniffs samples, the Thermal and Evolved-Gas Analyzer, or TEGA. A sample of clumpy soil dumped onto one TEGA oven on June 6 has yielded only a few particles passing through a mesh screen over the opening to the oven, even after additional vibration of the screen on Monday. The sprinkling method developed a few months ago by members of Phoenix's arm and microscope teams uses vibration of the tilted scoop by a motorized rasp to gently jostle some material out, instead of turning the scoop over to empty it. The rasp is located on the back of the scoop and will be used later in the mission to scrape up samples of subsurface ice. The first test of the sprinkling method Monday produced a layer of fine particles extending from a pile of about a tablespoon of soil. The practice placed the material on the top surface of the instrument suite that includes the microscope, the Microscopy, Electrochemistry and Conductivity Analyzer, or MECA. "This is good news," said Ray Arvidson of Washington University in St. Louis, lead scientist for the Robotic Arm. He said that the clumping tendency of Martian soil at the Phoenix site and some earlier landing sites comes from extremely fine particles filling in gaps between coarser, sand-size particles, perhaps together with an ingredient acting to cement particles together. Future soil samples may be prepared prior to delivery by chopping and scraping them with blades on the scoop. - 11/6/2008 - Comment {0} - Post Comment
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