VOL. 98 NO. 5 MAY 2017 Seafl oor in the MH370 Search Area What Is Snow Drought? Earth & Space Science News Earth’s Deep Carbon HOW HOT CAN ANTARCTICA GET? Earth & Space Science News Contents MAY 2017 PROJECT UPDATE VOLUME 98, ISSUE 5 24 Geological Insights from the Search for Malaysia Airlines Flight MH370 A rich trove of marine geophysical data acquired in the search for missing flight MH370 is yielding knowledge of ocean floor processes at a level of detail rare in the deep ocean. PROJECT UPDATE 30 Synthesizing Our Understanding of Earth’s Deep Carbon The Deep Carbon Observatory is entering a new phase, in which it will integrate 10 years of discoveries into an overarching model to benefit the scientific community 18 and a wider public. OPINION COVER Defining Snow Drought Evaluating the Highest Temperature 15and Why It Matters Swings from snow drought to extreme Extremes in the Antarctic winter rainfall make managing reservoirs The record high temperature for regions south of 60°S latitude is a balmy 19.8°C incredibly difficult. But what exactly is (67.6°F), recorded 30 January 1982 at a research station on Signy Island. “snow drought”? Earth & Space Science News Eos.org // 1 Contents DEPARTMENTS Editor in Chief Barbara T. Richman: AGU, Washington, D. C., USA; eos_ [email protected] Editors Christina M. S. Cohen Wendy S. Gordon Carol A. Stein California Institute Ecologia Consulting, Department of Earth and of Technology, Pasadena, Austin, Texas, USA; Environmental Sciences, Calif., USA; wendy@ecologiaconsulting University of Illinois at cohen@srl .caltech.edu .com Chicago, Chicago, Ill., José D. Fuentes David Halpern USA; [email protected] Department of Meteorology, Jet Propulsion Laboratory, Pennsylvania State Pasadena, Calif., USA; University, University davidhalpern29@gmail Park, Pa., USA; .com [email protected] Editorial Advisory Board Nathan T. Bridges, Planetary Sciences John W. Lane, Near-Surface Geophysics Mark G. Flanner, Atmospheric Sciences Jian Lin, Tectonophysics 43 Nicola J. Fox, Space Physics Figen Mekik, Paleoceanography and Aeronomy and Paleoclimatology Peter Fox, Earth and Space Science Jerry L. Miller, Ocean Sciences Informatics Thomas H. Painter, Cryosphere 34–39 AGU News Steve Frolking, Biogeosciences Sciences Edward J. Garnero, Study of the Philip J. Rasch, Global Environmental Getting to Fair: Recognizing Implicit Earth’s Deep Interior Change Bias and Easing Its Impact; Radio Michael N. Gooseff, Hydrology Eric M. Riggs, Education Brian C. Gunter, Geodesy Adrian Tuck, Nonlinear Geophysics Science and Space Weather Now Kristine C. Harper, History Sergio Vinciguerra, Mineral Available on IEEE Xplore; Outstanding of Geophysics and Rock Physics Student Paper Awards. Susan E. Hough, Natural Hazards Andrew C. Wilcox, Earth and Planetary Emily R. Johnson, Volcanology, Surface Processes Geochemistry, and Petrology Earle Williams, Atmospheric Keith D. Koper, Seismology and Space Electricity 40–43 Research Spotlight Robert E. Kopp, Geomagnetism Mary Lou Zoback, Societal Impacts and Paleomagnetism and Policy Sciences Polar Interlopers in the Aurora; After Decades, High- Altitude Staff Observations Revived at Jicamarca; Production and Design: Faith A. Ishii, Production Manager; Melissa A. Tribur, Senior 7 Production Specialist; Elizabeth Jacobsen, Production and Editorial Assistant; Karen River’s Rise Linked to Oklahoma’s Lomax, Acting Manager, Design and Branding; Travis Frazier and Valerie Friedman, Largest Earthquake; What Electronic Graphics Specialists Proportion of River Nutrients Editorial: Peter L. Weiss, Manager/Senior News Editor; Mohi Kumar, Scientific 3–9 News Content Editor; Randy Showstack, Senior News Writer; JoAnna Wendel, News Writer; Reaches the Open Sea?; Radar Liz Castenson, Editorial and Production Coordinator Lunar Lava Tubes Could Offer Method Shows Promise in Aquifer; Marketing: Jamie R. Liu, Manager, Marketing; Angelo Bouselli and Tyjen Conley, Future Moon Explorers a Safe When Income Goes Up, Does Marketing Program Managers Haven; Study Finds That Coastal Pollution Go Down? Advertising: Tracy LaMondue, Director, Development; Tel: +1-202-777-7372; Email: [email protected] Wetlands Excel at Storing Carbon; Scientists Witness Glacial Outburst ©2017. American Geophysical Union. All Rights Reserved. Material in this issue may 44–48 Positions Available be photocopied by individual scientists for research or classroom use. Permission is Flood Near Mount Everest; Images also granted to use short quotes, figures, and tables for publication in scientific books of Pan, Saturn’s Ravioli Moon, in Current job openings in the Earth and journals. For permission for any other uses, contact the AGU Publications Office. Unprecedented Detail; Kilimanjaro’s and space sciences. Eos (ISSN 0096-3941) is published monthly by the American Geophysical Union, 2000 Florida Ave., NW, Washington, DC 20009, USA. Periodical Class postage paid Iconic Snows Mapped in Three at Washington, D. C., and at additional mailing offices. POSTMASTER: Send address Dimensions. Inside Back Cover: changes to Member Service Center, 2000 Florida Ave., NW, Washington, DC 20009, USA. Postcards from the Field Member Service Center: 8:00 a.m.–6:00 p.m. Eastern time; Tel: +1-202-462-6900; 10–11 Meeting Report Explorers descend into an ice cave Fax: +1-202-328-0566; Tel. orders in U.S.: 1-800-966-2481; Email: service@ agu.org. Cities Smarten Up and Go Green; on Antarctica’s Mount Erebus. Use AGU’s Geophysical Electronic Manuscript Submissions system to submit Using Archives of Past Floods to a manuscript: http://eos-submit.agu.org. Estimate Future Flood Hazards. On the Cover Views expressed in this publication do not necessarily reflect official positions of the American Icicles hang from a melting iceberg Geophysical Union unless expressly stated. 12–17 Opinion near Petermann Island, off the Christine W. McEntee, Executive Director/CEO Airline Flight Paths over the Antarctic Peninsula. Credit: Danita Unmapped Ocean; Defining Snow Delimont/Gallo Images/Getty Drought and Why It Matters. Images. facebook.com/AmericanGeophysicalUnion @AGU_Eos linkedin.com/company/american-geophysical-union youtube.com/user/AGUvideos 2 // Eos May 2017 NEWS orbiter SELENE (Selenological and Engineering Lunar Lava Tubes Could Offer Explorer), also known as Kaguya. What the researchers didn’t know was whether the pit Future Moon Explorers a Safe Haven led to something larger below. Two narrow surface depressions called sinuous rilles, which scientists think represent collapsed portions of lava tubes, stretch away from the unar colonization isn’t mere science fic- flows, with basalt sometimes running as pit. Could the pit be a skylight opening to an tion anymore. Billionaires plan to send molten rivers. In these rivers, the outside intact lava tube’s long, narrow passage? L tourists on once- in- a- lifetime trips, and cools faster than the inside, creating a hard Ancient basaltic lava flows called maria politicians say that they hope to colonize the shell. The remaining lava pours out, leaving a cover much of the Moon, similar to the much Moon in the next few decades. There may even hollow space behind. younger Columbia River basalts in the western be ways for human colonists to harvest water Do similar lava tubes exist on the Moon? United States. Because the Moon’s gravity is from ice that may be permanently shadowed In a presentation on 22 March at the one sixth that of Earth’s, gravity doesn’t in certain caves. 48th Lunar and Planetary Science Conference But where could a human colony actually (LPSC) in The Woodlands, Texas, Junichi live? The Moon has no atmosphere or mag- Haruyama, a senior researcher at the Japan If humans ever got access netic field to shield it from solar radiation, Aerospace Exploration Agency (JAXA), dis- to the tubes, “the science and micrometeorites constantly rain onto its cussed one such lava tube that he suspects surface. That’s no environment for our may be snaking underneath the Moon’s sur- would be amazing.” squishy, earthling bodies. face. Scientists studying the Moon’s surface may have found the answer: Humans could shelter Searching for Lava Tubes in lunar lava tubes. The Moon is covered in In 2009, Haruyama and his team spotted evi- impede lava flow as much, allowing lava to huge swaths of ancient basaltic lava flows. dence of a dark hole in the Moon’s Marius spread widely across the surface. Nonetheless, Earth’s volcanoes can also erupt in similar Hills region in data from the Japanese lunar lunar lava tubes may have formed in an Earth- like way, Haruyama said. Last year, another team spotted gravity anomalies that suggested hollow, narrow spaces around the Marius Hills pit. These data came from NASA’s Gravity Recovery and Inte- rior Laboratory (GRAIL) mission, which con- sists of two spacecraft orbiting the Moon. The orbiters can detect these anomalies by mea- suring how much the Moon’s gravity tugs on them. Areas of more mass tug on the space- craft more, whereas hollow areas have less mass and so tug on GRAIL less. To confirm GRAIL’s findings, Haruyama and his colleagues turned again to SELENE’s data, looking closer at the sinuous rilles. They spe- cifically looked at data from SELENE’s Lunar Radar Sounder (LRS), which imaged the sub- surface using low-frequency​­ radio waves. The LRS data revealed hollow space more than 100 meters deep in some places and tens of kilometers long underneath one of the rilles near the pit. The pit itself looked to be 50 meters deep. These data led researchers to believe that the pit could, indeed, be a col- lapsed portion of a lava tube roof. These data also match the gravity readings from GRAIL, Haruyama said. Exploring the Tubes If humans, via rover or their own two feet, ever got access to the tubes, “the science would be amazing,” said Brent Garry, a geo- physicist at NASA Goddard Space Flight Cen- NASA/GSFC/Arizona State University State NASA/GSFC/Arizona ter. The tube’s interior tempts with pristine The Marius Hills pit on the Moon, spotted in 2009 by scientists at the Japan Aerospace Exploration Agency.