Eos,Vol. 84, No. 33, 19 August 2003

the lava’s melting temperature at surface pres- can be lost entirely from Io or cold-trapped at Keszthelyi, L., and A. McEwen, Magmatic differentia- sure.However,for lava at 1870 K to have a stable sites,compositional evolution of evapo- tion of Io, Icarus 130, 437–448, 1997. basaltic composition (with liquidus melting rated lava residues would affect igneous Lopes, R., et al., Io in the near-infrared: NIMS results temperatures ~1400–1550 K at 1 bar),the magma phase equilibria and the temperature of subse- from the Galileo fly-bys in 1999 and 2000,J. Geo- would have to ascend rapidly from nearly phys. Res. 106, 33,053–33,078, 2001. quent eruptions.Refractory lava residues lack the Lopes-Gautier,R., et al.,A close-up look at Io in the 1,000 km deep with little cooling in transit. amounts of SiO2 and FeO in common silicate infrared: Results from Galileo’s near-infrared map- Though no record of such an eruption exists lavas (Figure 3b) and may have extraordinary ping spectrometer, Science, 288, 1201–1204, 2000. on Earth, magma may have erupted from liquidus temperatures (Figure 3c). Marchis, F., et al., High-resolution Keck adaptive nearly such depths on Earth’s moon.Alternatively, optics imaging of violent volcanic activity on Io, Io’s magmas could be heated near the surface Questions Still to be Answered Icarus 160, 124–131, 2002. by the electrical induction currents and McEwen et al., High-temperature silicate volcanism plasma currents bathing Io.Heating in a tidally The epic tour of the Jovian system by Galileo on Jupiter’s moon,Io,Science, 281, 87–90, 1998. deforming dike is inadequate to heat basaltic has expanded our vision of what is possible McEwen,A. S. et al., Galileo at Io: Results from high- lavas to the highest temperatures seen on Io, in this universe. Io has its own unique and resolution imaging,Science, 288, 1193–1198, 2000. according to our calculations. hyperactive behavior that has been produced Stolyarova,V.L.and G.A.Semenov,Mass Spectrometric Vapor distillation and “ceramic volcanism.” by and may have affected its global chemical Study of the Vaporization of Oxide Systems, 434 evolution. Unsolved puzzles regard the range pp., John Wiley & Sons, Inc., New York, 1994. Lava outside the basalt-peridotite-komatiite Williams,D.A.,A.H.Wilson,and R.Greeley,A komatiite system is conceivable due to Io’s unique his- of silicate lava compositions and eruption temperatures and the mechanisms by which analog to potential ultramafic materials on Io, tory of intense, high-temperature magmatic J. Geophys. Res. 105, 1671–1684, 2000. such large volumes of lava are transported processing.The partial vapor pressures of SiO, Williams,D.A.,A.G.Davies,L.P. Keszthelyi,and R.Greeley, through the crust. How can Io maintain its Mg,Fe,FeO,and other gases of common oxide The July 1997 eruption at Pillan Patera on Io: Impli- high magma temperatures without being and silicate systems exceed nanobars at 1500 cations for ultrabasic lava flow emplacement, almost totally molten? Is Io a crusted magma K and approach microbars at 1900 K [Stolyarova J. Geophys. Res. 106, 33,105–33,119, 2001. ocean, and if so, how does Io maintain a suffi- and Semenov, 1994].Vaporization of metals ciently thick and strong lithosphere to support from hot lava can be significant when exposed mountains higher than Mount Everest? Is Io a Author Information on flow surfaces and through cracks in solidi- refractory cinder-like body,like a giant mete- fying crusts, especially if fluxed by sulfurous oritic calcium-aluminum-rich inclusion (with Jeffrey Kargel,Robert Carlson,Ashley Davies, Bruce volatiles.Vapor pressures and lava evolution added volatiles)? Why does Io have an extremely Fegley Jr.,Alan Gillespie,Ronald Greeley,Robert Howell, due to fractional vaporization were calculated volatile,sulfur-rich surface,yet water,carbon Kandis Lea Jessup,Lucas Kamp, Laszlo Keszthelyi, for the system Si-Na-K-Mg-Fe-Ca-Al-Ti-O (L. dioxide, and many other volatiles are absent? Rosaly Lopes,Timothy MacIntyre,Franck Marchis, Schaefer and B. Fegley,Washington University, How are we to reconcile Io’s peculiar volatility Alfred McEwen, Moses Milazzo, Jason Perry,Jani unpublished data, 2002). Results for an initial with high-temperature global processing? Radebaugh, Laura Schaefer,Nicholas Schmerr, Barberton high-MgO komatiite at 1900 K are Future space missions and astronomical William Smythe, John Spencer,David Williams, given in Figure 3. Initial vapors are dominated observations could give definitive answers Ju Zhang, and Mikhail Zolotov by Na and K (not shown) and oxygen species. to these questions. Pressures of other gases, though lower,are For more information, contact Jeff Kargel, U.S. orders of magnitude larger than Io’s ambient References Geological Survey,Flagstaff,Ariz.; E-mail: jkargel@ surface pressure.Following rapid loss of alkalis, Davies,A. G., et al.,Thermal signature, eruption style, usgs.gov.

vapors are dominated by SiO,Fe, FeO,Mg, O2, and eruption evolution at Pele and Pillan on Io, and O (Figure 3a). If metal and oxide vapors J. Geophys. Res. 106, 33,079–33,103, 2001.

expensive, are not available daily,and are lim- MODIS Detects Oil Spills in Lake ited by sea state [Liu et al., 2000].The optimal wind speed to effectively detect oil spill slicks by SAR is about 1.5 to 6 m/s.Other features, Maracaibo,Venezuela such as phytoplankton slicks and fresh water slicks,may present interference and cause false PAGES 313, 319 area covered, or duration of the spills. Clear detection [Lin et al., 2002].Traditional satellite images of the spill were captured with NASA’s optical sensors (e.g.,CZCS, SeaWiFS,AVHRR) have not been of much use for oil spill detection Starting December 2002, the oil industry Moderate Resolution Imaging Spectroradiometer due to coarse spatial resolution (~ 1 km per operating in and around Lake Maracaibo in (MODIS),however. MODIS is effectively a sophis- pixel),lack of coverage,cloud cover interference, Venezuela suffered a series of accidents ticated digital camera launched aboard the and lack of algorithms for data processing and (Figure 1).Fires,the sinking of two barges,rup- Terra satellite in December 1999, and aboard interpretation [Fingas and Brown, 1997, 2000]. ture of oil pipelines, spills from floating oil the Aqua satellite in April 2002 [Esaias et al., High-resolution optical sensors (e.g.,Landsat storage and transfer stations,and malfunctioning 1998; http://modis. gsfc.nasa.gov]. Its medium- ETM+,SPOT,IKONOS) do not provide daily of oil extraction platforms led to extensive oil resolution bands (250 and 500 m resolution) observations, and the data with limited spatial spills.Local and federal Venezuelan government are available to the public, and have great coverage are expensive. Here we show that oil industry experts directly observed the series potential in coastal monitoring.This article new optical sensor technologies provide an of spills from aircraft, helicopter,and various demonstrates how MODIS can provide basic unprecedented capability for oil spill moni- surface vessels.The spills were recorded in and critical assessments of oil spills. toring in marine environments. December by official photography and video Remote Sensing of Oil Spills: Background of leaking infrastructure,and unofficial recordings MODIS Imagery of Oil Spills continued in January and February 2003 Techniques for remote sensing of aquatic oil (http://www.comlago.com.ve/fotosvideos.html). spills includes optical (passive visible and In the past, oil crude has been considered These surveys did not provide sufficient spatial infrared, and laser fluorosensors), microwave, to have a higher surface reflectance than water or temporal coverage to assess the magnitude, and radar (e.g., Synthetic Aperture Radar) in the visible region of the electromagnetic approaches using aircraft or satellites [see spectrum, but no distinctive spectral charac- BY CHUANMIN HU,FRANK E. MÜLLER-KARGER, reviews by Fingas and Brown, 1997,2000]. teristics that would allow its differentiation CHARLES (JUDD) TAYLOR,DOUGLAS MYHRE,BROCK Airborne assessments are limited by high cost. from the background under solar illumination MURCH,ANA L. ODRIOZOLA, AND GONZALO GODOY Satellites have other limitations. SAR data are [Fingas and Brown, 1997; and references Eos,Vol. 84, No. 33, 19 August 2003 therein]. However,recent optical modeling by Otremba and Piskozub [2001, 2003] demon- strates that there is a reflectance contrast between an oil film on the sea surface and background turbid water,so that the oil film can be detected under appropriate solar/ viewing geometry and wind speeds. The problems of the oil industry in Venezuela received international news coverage (e.g., The Miami Herald, http://www.miami.com/ mld/miamiherald/4993381.htm; Reuters News Service, http://www.planetark.org/avantgo/ dailynewsstory.cfm?newsid=19401).On becoming aware of what had happened, we decided to examine the real-time MODIS data, collected and archived by an X-band ground station at the University of South Florida at St.Petersburg, to assess whether any pattern that might be related to oil spills over water in Lake Mara- caibo could be detected. We examined the medium-resolution (250- and 500-m) MODIS Level-1 total radiance imagery from 1 December 2002 to 9 March 2003. Of the 68 daily image sets (some gaps exist due to ground X-band antenna malfunc- tion), over half contain cloud cover < 50%. About a dozen images showed patterns within Lake Maracaibo that we suspected could be extensive spill patches.Such patterns were visible even when significant Sun glint contamination was present. We discounted the possibility that these fea- tures could be due to phytoplankton blooms, because such blooms occur mainly along the coast and near large population centers during the rainy season (April-May and October- November), due to runoff.The dark features observed in the MODIS data occurred during the dry season and away from the traditional areas of blooms.Further,there are ample direct Fig. 1. Oil spill slicks in Lake Maracaibo,Venezuela.From top left, clockwise: MODIS 250-m observations that the features in the images (620–670 nm) image taken on 18 January 2003 (white color represents clouds,land,or extreme correspond to oil-contaminated waters.Spectral turbidity near the coast; arrow with broken line indicates current direction,according to observation analysis (see below) also suggests that these and numerical model simulations); enlarged image of the region of major oil slicks (even smaller features are not due to algal blooms.A com- slicks can be viewed at full resolution).Inset shows location of the lake.Bottom: airborne photo- plete time series of these images can be found graph (courtesy of Gobernación del Estado Zulia,Venezuela).Complete time-series of MODIS at http://modis.marine. usf.edu/products/ images are available at http://modis.marine.usf.edu/products/maracaibo/. maracaibo/. Here we focus on a few examples for illus- patches changed. Slicks on 16 and 18 January speed and solar/viewing geometry [Otremba trative purposes. Figure 1 shows a 250-m reso- were located in the western part of central and Piskozub, 2003].To better examine the lution MODIS image illustrating the slicks of Lake Maracaibo. On 20 January,only one large contrast, the atmospheric radiance had to be oil spilled in Lake Maracaibo.The slicks were patch (~ 32 km2) was observed in this location, removed to obtain the water-leaving radiance detected because of their negative contrast but other patches were found in the eastern or surface reflectance.When first processed relative to surrounding waters [oil slicks are part of the lake. using the standard MODIS ocean codes darker; see Otremba and Piskozub, 2001]. Official reports of oil spills from drilling and (U. Miami/RSMAS), the large slicks showed Using the software,Environment for Visualizing storage platforms in eastern Lake Maracaibo positive contrast in water-leaving radiance Images (ENVI, Research Systems, Inc.©), we surfaced only on 30 and 31 January 2003.The data (1-km resolution),due to erroneous atmos- estimated the number of oil-contaminated pix- satellite images suggested that the oil spill pheric correction.We knew that the standard els at ~2163, corresponding to an area of ~133 event started earlier than reported.In an image procedure to remove atmospheric radiance km2. Some slicks may be masked by clouds, taken 26 December 2002, we identified slicks from the data was inadequate for turbid and therefore, the spill may be larger.Because similar to those in the 16 and 18 January images. water.We re-processed the data using atmos- of limitations of the print media,the full MODIS pheric properties derived from within the resolution is hard to appreciate in Figure 1. Optical Signature dark oil patch, and applied those to the sur- Smaller slicks are visible by displaying and rounding water [as per Hu et al., 2000]. Figure zooming the image on a computer screen. Figure Of all the MODIS images examined,including 3 shows the reflectance before and after the 2 presents more dark water features on 16 those under direct Sun glint, none has shown atmospheric correction along a transect line and 20 January 2003.Local authorities validated positive contrast between oil spill patches drawn across the spill slick (Figure 1). Clearly, these features to be oil slicks.These covered and surrounding waters.The negative contrast the contrast between the patch and surrounding ~138 km2 (2244 pixels) and 136 km2 (2216 suggested that the spill dispersed as an oil waters was enhanced after proper correction. pixels), respectively.The area covered by the film floating on the surface,and not as droplets Any image-enhancing software can be used spill was similar over about 5 days (16, 18, and suspended in the water.The latter will always to contrast-stretch an image to help identify 20 January), but the spatial distribution of the display positive contrast, regardless of wind and trace a slick in MODIS data. However, Eos,Vol. 84, No. 33, 19 August 2003 proper atmospheric correction,as used here, provides meaningful geophysical data.Accu- rate radiances/reflectances offer the potential to derive oil film thickness,if a reliable empirical optical model has been established a priori with in situ measurements. For example, the contrast of the Lake Maracaibo slicks is higher than that found by Otremba and Piskozub [2001].This suggests that the film may be thicker (i.e., have more absorption) than assumed in their simulations (5 µm). Clearly, the degree of turbidity underneath and around the patch also plays a role in deriving accurate results in such empirical approaches. From the perspective of aquatic optics, and without any prior knowledge of local biogeo- chemical processes or oil spills, it would be difficult to identify the patterns observed as oil slicks. Phytoplankton blooms can be ruled out because of the reasons mentioned above, and because they would typically have a pos- itive contrast at 555- and 645-nm due to ele- vated backscattering.The reflectance contrast Fig. 2. MODIS images (841–876 nm) showing oil spill slicks in Lake Maracaibo. Major slicks are at multiple wavelengths provides more infor- marked with arrows.White color represents clouds or extreme turbidity near the coast. Many mation than SAR imagery,where phytoplankton smaller slicks can be viewed by displaying the image at full resolution. bloom can also dampen the signal [Lin et al., 2002].Yet it is currently not possible to estab- lish an automated feature recognition system that identifies oil spill events. External knowl- edge about the region,environment,and current events needs to accompany visual examination of the satellite imagery to discriminate between various events.

Future Directions Traditional satellite ocean color sensors typ- ically have ground resolution of about 1 km, making it difficult to detect small features such as oil spill slicks. In contrast, the medium-resolution (250- and 500-m) MODIS channels show great potential for daily moni- toring of the coastal environment because of Fig. 3.At-sensor reflectance (left) and surface remote sensing reflectance (right) for several MODIS 2 their unprecedented synoptic and repetitive bands across the transect line shown in Figure 1. Each pixel is about 250 x 250 m in size (the 555- and 469-nm data are interpolated from the original 500-m resolution). coverage with fine resolution. Our findings show that there is no good reason to continue minimizing the potential of optical satellite sensors to detect oil spill events.We now need to with 14 of these in the United States (http:// thank NASA Headquarters (James Dodge) and develop strategies to fully integrate these satellite rsd.gsfc.nasa.gov/eosdb/).This infrastructure SeaSpace Corporation for their support and sensors into our incipient Integrated Ocean allows repeated coverage of a significant assistance in conducting the assessments Observing System (http://www.ocean.us).Our portion of the globe’s coastal areas.At the described here. IMaRS contribution #0057. vision is one in which automated sentinels University of South Florida, we are generating issue alarms for events like oil spills or harmful online,interpreted,medium-resolution products References algal blooms [SWFDOG, 2002].At this stage, that are tailored to support coastal resource intelligent interpretation from a well-trained managers, educators, and the public.We find Esaias,W.E.,et al.,An overview of MODIS capabilities remote sensing practitioner is required, but the EOS platforms to be excellent for devel- for ocean science observations,IEEE Trans.Geosci. we need to develop both stable and accurate oping science-based applications in prepara- Remote Sens., 36, 1250–1265, 1998. radiance products,as well as good empirical tion for the National Polar-Orbiting Operational Fingas,M.,and C.Brown,Remote sensing of oil spills, Sea Technology,38, 37–46, 1997. Environmental Satellite System (NPOESS) algorithms for coastal zones, so that reliable Fingas, M., and C. Brown, Oil-spill remote sensing - sentinels can be constructed.The medium- and the NPOESS Preparatory mission, to be An update, Sea Technology,41, 21–26, 2000. resolution MODIS imaging bands were designed launched toward the end of the first decade Hu,C.,K.L.Carder,and F.E.Müller-Karger,Atmospheric for land. Quantitative use of these bands for of the new millennium. correction of SeaWiFS imagery over turbid coastal coastal water monitoring still needs to be waters: a practical method, Remote Sens. Environ., 74, 195–206, 2000. investigated. In particular,reliable, operational Acknowledgments atmospheric correction and bio-optical inversion Lin, I.-I., L. S.Wen,K.-K. Liu, and W.-T.Tsai, Evidence codes need to be developed to obtain surface This work was supported by NASA grants and quantification of the correlation between radar backscatter and ocean colour supported by reflectance and the associated water parameters, NAG5-10738 and NAG5-11254, and by a con- simultaneously acquired in situ sea truth,Geophys. such as suspended sediment and chlorophyll tract (#03-751) from the Cooperative Institute Res. Lett. 29, 102.1-4, 2002. concentrations. for Coastal and Estuarine Environmental Liu,A.K.,S.,Y.Wu,W.Y.Tseng,and W.G.Pichel,Wavelet As of August 2001,49 MODIS direct broadcast Technology (CICEET) between NOAA and the analysis of SAR images for coastal monitoring,Can. (DB) receiving stations were active worldwide, University of New Hampshire.We particularly J. Rem. Sens., 26, 494–500, 2000. Eos,Vol. 84, No. 33, 19 August 2003

Otremba, Z., and J. Piskozub, Modeling of the optical SWFDOG,Satellite images track “black water”event ozola,University of South Florida,St.Petersburg; and contrast of an oil film on a sea surface,Optics off Florida coast,Eos Trans.,AGU,83,281,285,2002. Gonzalo Godoy,Comisión Ejecutiva para el Manejo Express., 9, 411–416, 2001. Author Information Integral del Lago de Maracaibo y su Cuenca Hidro- Otremba,Z.,and J.Piskozub,Modeling the remotely gráfica,Gobernación del Estado Zulia,Venezuela sensed optical contrast caused by oil suspended in Chuanmin Hu,Frank E.Müller-Karger,Charles (Judd) For additional information,contact Chuanmin Hu the sea water column,Optics Express.,11,2–6,2003. Taylor,Douglas Myhre, Brock Murch, and Ana L. Odri- via e-mail at [email protected].

inherent in getting people and political enti- Advancing Ideas, Methods in Interdisciplinary ties to acknowledge climate change and pur- Climate Change Research for New Ph.D.s sue its mitigation.Another lengthy discussion focused on mentoring.From these sessions, participants began to learn how to assemble PAGES 314, 320 First Symposium Held an interdisciplinary team to cover the range of expertise necessary to address the issues of The first part of the symposium was dedicated climate change. The global environmental changes that the to sharing each participant’s doctoral work. To help the group more successfully work in Earth is experiencing today impact the smallest Due to the variety of scientific disciplines repre- teams, communication consultant Chris Olex of organisms to global biogeochemical cycles. led sessions on communication skills and Climate change, one of the most noticeable sented,many key elements of current climate change research were presented.Topics included: working group dynamics.Another important alterations, is at least partly caused by our aspect of being a scientist is sharing your work influence on worldwide physical, chemical, G Climate modeling and atmospheric science. with the wider public.Ashley Simons of SeaWeb and biological systems. Climate change also The impact of aerosols, ozone, dust, pollution, focused on communicating beyond academia, has strong implications for political,economic, and clouds on climate; El Niño-Southern both with the public and the press.The sugges- and social policy.Because climate change Oscillation (ENSO); tions presented by these two experts apply both affects such a wide variety of disciplines and G Paleoclimate.Evidence for climate variability to speaking and to writing effectively,skills people,pursuing research in this field requires from cave stalagmites,Scottish pine,and marine that new scientists often have not extensively an interdisciplinary approach.This need to and lake sediments; glacial-interglacial variability practiced. simultaneously understand climate change and of sea ice and the carbon cycle; forecast and effectively deal with its impacts on G Modern climate. Links to biogeochemical “Ideal” Climate Change Program present and future generations presents a great cycling,lake ecosystems,carbon sequestration challenge to the global research community. in forests, the hydrological cycle, terrestrial One of the most important parts of the sym- With this perspective in mind,the Dissertations habitat loss, and biodiversity; posium was a session during which participants Initiative for the Advancement of Climate Change G Tropical climate change.Relation to variation were asked to design the “ideal”climate change Research (DISCCRS) was formed in 2002 to in coral growth,tropical trees,and ecosystems; Ph.D.program.We discussed the positive and bring together recent Ph.D.recipients across G High-latitude climate change. Relation to negative aspects of our respective Ph.D.pro- the range of disciplines whose work involves Arctic sea ice, the carbon cycle in the Arctic grams and tried to identify program compo- climate change and its impacts. tundra and the upper ocean, and glacier nents that would be more conducive to creating DISCCRS is a multi-agency and multi-organi- dynamics; an environment of “interdisciplinarity”and zation initiative sponsored by the American G Social science. Policy development and bestowing general knowledge in climate Geophysical Union,the American Meteorological conflict resolution in environmental and change. It was commonly agreed that any Society,the American Society of Limnology developmental negotiations. climate change researcher needs a disciplinary and Oceanography,the Ecological Society of anchor for credibility and for finding job America, and Whitman College; and funded As can be seen by the list above,correlations opportunities. by NASA’s Office of Earth Science and the U.S. were demonstrated between climate and However,many had difficulty finding super- National Science Foundation’s Geosciences many different natural systems. Implications visors and program components that went Directorate (Climate Dynamics and Education for the future were woven into both formal beyond this disciplinary structure and fostered and Human Resources).The goal of DISCCRS presentations and informal discussions. In the pursuit of interdisciplinary research. It was is “to catalyze interdisciplinary understanding addition, many of the social and political diffi- suggested that, rather than creating a specific and peer networking among recent grads”by culties of mitigating for and adapting to department or degree in climate change,the bringing them together via several different climate change were highlighted. By showing ideal program would give students access to a avenues.These various avenues are a Ph.D.Dis- just how pervasive the impacts of climate climate change institute on campus from which sertation Registry that is accessible online change are on our world and how tricky it is he or she could take courses and pursue a (over 200 dissertation abstracts were registered to deal with them, these presentations laid the minor,in addition to the disciplinary major. during the program’s first year;see http://aslo.org/ foundation for the rest of the week: the truly The institute faculty could serve as co-advisors. phd.html),an electronic message board that interdisciplinary part of the symposium. In addition to interdisciplinary scientific training, fosters communication among the DISCCRS For the next 4 days, the participants worked the ideal programs would train students to registrants,and a capstone symposium that brings together to develop interdisciplinary strategies work effectively as part of an interdisciplinary the registrants together to introduce the concept for defining the complex processes and inter- team. of interdisciplinary research and its many pos- actions of climate change and its impacts.Formal To pursue professional research, knowledge sibilities. discussions were formed around topics that of funding opportunities and training in pro- The first of these symposia was held 10–15 were chosen by the group.These included the posal development is essential. Representing March 2003, in Guanica, Puerto Rico.The implications of climate change for species the U.S.National Science Foundation,Fae Korsmo week-long event brought together 40 recent interactions,forests,and biogeochemical cycles, gave an overview of programs relevant to inter- graduates from 36 institutions and 11 countries. as well as ways in which temporal (fast versus disciplinary research in climate change.Korsmo, The participants were selected by a committee slow), spatial (large versus small),and ecologi- symposium organizer Susan Weiler,and two from among 72 applicants. Excellence and cal (species versus ecosystem) scales affect established DISCCRS interdisciplinary mentors, diversity of research background were the pri- our ability to do research and properly under- Jerry Mahlman and Ronald Mitchell, provided mary selection criteria to ensure that the par- stand our results.A large group discussed the practical guidelines for writing quality proposals. ticipants represented a range of expertise. politics of climate change and the difficulties Jerry,an atmospheric scientist, and Ron, a