February Geology and GSA Today media highlights

Volcanic and impact deposits of the Moon's Aristarchus Plateau: A new view from Earth-based radar images
Bruce Campbell et al., National Air and Space Museum, MRC 315, 4th and Independence Avenue, SW, Washington, D.C. 20560, USA. Pages 135-138.

Ancient volcanic eruptions on the Moon produced deposits of fine-grained, often glass-rich, pyroclastic material. In some places, like the Aristarchus Plateau, these deposits can be 20-30 meters thick. The pyroclastics are of interest for their association with early lunar volcanic processes, and as possible sources of materials for lunar outposts. Campbell et al. used new radar images from Earth-based radio telescopes that penetrate the mantling layers to "see" the underlying terrain, to reveal details of the geologic events that shaped the Aristarchus Plateau. Radar data at longer wavelengths show the extent of lava flows that cover a significant portion of the plateau. When struck by relatively small meteorites, these lava flows are broken up into rocks and mixed into the fine-grained layers above. Such abundant rocks might complicate the use of the pyroclastics as a resource for future lunar explorers. The new radar data can be used to identify thick, rock-poor areas of the pyroclastic deposits best suited for resource recovery.

A new model linking atmospheric methane sources to Pleistocene glaciation via methanogenesis in sedimentary basins
Steven Petsch et al., Department of Geosciences, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA. Pages 139-142.

Natural gas is an important fossil fuel resource composed largely of methane. Methane is also a significant greenhouse gas and, like carbon dioxide, methane concentrations in the atmosphere have increased greatly as climate shifted from cold to warm at the end of the last Ice Age. Formolo et al. suggest how, in rocks from northern Michigan, fossil fuel methane may be connected to methane as a greenhouse gas. Many thousands of years ago, microorganisms were stimulated to produce methane deep underground through decomposition of ancient sedimentary rocks when those rocks were covered by large continental ice sheets. Formolo et al. show that this subsurface microbial activity is recorded in biodegraded oil-like compounds, as well as in the DNA of microorganisms still active deep within these rocks. As long as an ice sheet remained over Michigan, methane produced by these microorganisms remained trapped underground. Once the ice began melting, however, methane that had accumulated over thousands of years was rapidly released to the atmosphere, accelerating greenhouse gas warming of the planet. Natural gas currently recovered as a fossil fuel resource in Michigan and other locations may thus represent just a small fraction of methane produced by subsurface microorganisms, most of which long since escaped to the atmosphere and contributed to climate change.