What's new in exploration

	Vol. 226 No. 1
PERRY A. FISCHER, EDITOR

Mid Ocean Ridge ethane. A team of University of Minnesota scientists has discovered how methane, ethane and higher hydrocarbons can be generated on, and beneath, the seafloor. The hydrocarbons are abiogenic (non-biological in origin), and are created when iron- and chromium-rich rocks react with superheated fluids circulating deep beneath the seafloor near ocean-ridge spreading centers. The researchers presented a portion of their work in December at the American Geophysical Union meeting in San Francisco.

In the laboratory, the researchers recreated the conditions (> 700 °F, 5,900 psi) that exist on the ocean bottom in parts of the Mid-Atlantic Ridge. The ridge contains hydrothermal vents, which spew superheated fluids into the seawater. The team found that under such conditions, hydrocarbons – methane, ethane and propane – could be produced on the surface of minerals rich in iron and chromium. These hydrocarbons are likely food for the diverse communities of life that typically thrive around hydrothermal vents.

This hydrocarbon genesis occurs in two steps. First, an iron compound in rock strips water of its oxygen, liberating hydrogen gas. Then, CO₂ from the degassing of magma reacts with the hydrogen to produce methane and water. The team discovered that rocks rich in chromium minerals accelerate the second step, while also producing more of the complex ethane and propane hydrocarbons.

While the CO₂-plus-hydrogen reaction is well known to chemists, forming hydrocarbons more complex than methane has been difficult. This work shows how it could happen. One geophysicist commented, “Chemists might want to tweak this process and see if they can produce hydrocarbons more efficiently. We wanted to get clues about what goes on in hydrothermal vents and to understand how hydrocarbon gases are generated in the continental and oceanic crust.”

In related work, researchers have built chemical sensors that can be placed in hydrothermal vents to measure such items as acidity, and gases like hydrogen and hydrogen sulfide. Acidity also seems to play a role in hydrocarbon synthesis in submarine hydrothermal systems. To access the vents as deep as two miles deep, the researchers use the submersible ALVIN.

Martian methanogens? It’s been a developing story, but now a third team of scientists has reported that Mars’ atmosphere contains methane. So, it’s probably going to stick. At first glance, this may not seem startling. But the details have potentially profound implications.

Since methane is the simplest hydrocarbon, comprising just one carbon atom, it is also the easiest to create. So, it’s not surprising that it is the most ubiquitous hydrocarbon. It is found on all the solar system planets – now including Mars – except Venus and Mercury. On all of the outer planets (Jupiter and beyond), methane is believed to originate from high-altitude photochemical reactions, or remain from primordial sources. On Saturn’s moon, Titan, its relative abundance (plus several more complex hydrocarbons) might be due to an exchange with surface sources. This is now creating considerable discussion and excitement, as the Cassini spacecraft prepares to launch the European Space Agency’s Huygens Probe, which should happen Christmas Day, for a parachute descent to Titan’s surface on January 15, 2005.

Modeling suggests that the gas giants should have no trouble holding on to their methane because of their immense gravity, but this is not true of Earth, Titan, and now Mars. In addition, methane is fragile in air and easily broken apart when hit by ultraviolet light. We know of most of the methane sources on Earth; Titan is a shrouded, unfolding enigma; and now Mars enters the fray with its own mystique.

At last month’s meeting of the American Astronomical Society’s Division for Planetary Sciences, Dr. Michael Mumma, a senior scientist at NASA’s Goddard Space Flight Center, reported three years of observations had provided strong evidence for methane on Mars. “We are 99% confident,” Dr. Mumma said. “It surprised all of us, actually. We really are still scrambling to understand what it means.” Modeling calculations indicate that the Martian methane must have been put there within the past 300 years. Further, there are some indications that the methane is not evenly distributed, that it might derive from localized sources. So the question is, “What is the source of the Martian methane?”

Only two plausible explanations have been offered: geothermal chemical reactions involving water and heat, like those that occur at the aforementioned hydrothermal vents on the seafloor; and life. The first requires appreciable quantities of liquid water, the second requires microbial life. Either of these once-fantastic explanations still involves some heady stuff. Frozen water? Sure. It’s been know to exist on Mars for many years. But there are no signs that any volcanism has occurred there for millions of years, and an instrument aboard NASA’s Mars Odyssey looked for warm spots on Mars’ surface and did not find any. Dr. Vladimir Krasnopolsky of Catholic University in Washington, the leader of one of the teams, said he believed bacteria to be the “most plausible source.” Not everyone agrees. One group used the Canada-France-Hawaii Telescope in Hawaii. Another team used the European Space Agency’s Mars Express mission. The third group used NASA’s IRTF on Mauna Kea, and the Gemini South telescope in Chile. Thinking of becoming a planetary geologist? You could not pick a more exciting time.

Noteworthy discovery. Niko Resources Ltd. hit a very significant amount of gas in Bangladesh. The Bangora-1 well was drilled to a depth of 11,930 ft and encountered numerous gas bearing reservoirs from 8,465 to 10,778 ft, with 285 ft gross thickness. The three lowermost zones were production tested, showing an aggregate flowrate more than 120 MMcfd at flowing pressures over 2,000 psi from individual sands. Gas quality is high, with 99.13% combustible gases. In addition, at least three other potential gas bearing sands, identified from logs, will be tested in a subsequent well. Niko has now had gas discoveries at each end of a 25-mi long anticlinal structure located within Block 9. The company will carry out further seismic and appraisal drilling over the structure. Niko holds a 60% interest, while Tullow Bangladesh Ltd. has 30%, and Bangladesh Petroleum Exploration and Production Ltd. has 10%.