Nov 30 2010
From The Space Library
RELEASE: 10-173
FIRST MAP OF GLOBAL FOREST HEIGHTS CREATED FROM NASA DATA
WASHINGTON -- Scientists have produced a first-of-its kind map of the height of the world's forests by combining data from three NASA satellites. The map will help scientists build an inventory of how much carbon the world's forests store and how fast that carbon cycles through ecosystems and back into the atmosphere. Maps of local and regional forest canopy have been produced before, but the new map is the first that spans the entire globe using one uniform method. The map was based on data collected by NASA's Terra and Aqua satellites, along with the Ice, Cloud and land Elevation Satellite, or ICESat. Michael Lefsky, a remote-sensing specialist from Colorado State University in Ft. Collins, produced the final product. Lefsky describes his results in a journal paper to be published next month in Geophysical Research Letters. The new map shows the world's tallest forests are clustered in North America's Pacific Northwest and portions of Southeast Asia. Shorter forests are found in broad swaths across northern Canada and Eurasia. The primary data Lefsky used was from a laser technology called lidar on the ICESat. Lidar can capture vertical slices of forest canopy height by shooting pulses of light at the ground and observing how much longer it takes for light to bounce back from the surface than from the top of the forest canopy. Since lidar can penetrate the top layer of forest canopy, it provides a detailed snapshot of the vertical structure of a forest. "Lidar is unparalleled for this type of measurement, Lefsky said. It would have taken weeks or more to collect the same amount of data in the field by counting and measuring tree trunks that lidar can capture in seconds. Lefsky based the map on data from more than 250 million laser pulses collected during a seven-year period. Because each pulse returns information about a tiny portion of the surface, lidar offered direct measurements of only 2.4 percent of the Earth's forested surfaces. To complete the map, Lefsky combined the lidar data with information from the Moderate Resolution Imaging Spectroradiometer (MODIS), an instrument aboard NASA's Terra and Aqua satellites. MODIS observes a broad swath of Earth's surface, even though it does not supply the vertical profile. The new results show that temperate conifer forests -- which are extremely moist and contain massive trees such as Douglas fir, western hemlock, redwoods, and sequoias -- have the tallest canopies, soaring above 131 feet. In contrast, boreal forests dominated by spruce, fir, pine, and larch had canopies typically less than 66 feet. Relatively undisturbed areas in tropical rain forests were about 82 feet tall, roughly the same height as the oak, beeches, and birches of temperate broadleaf forests common in Europe and much of the United States. Measuring canopy height has implications for efforts to estimate the amount of carbon tied up in Earth's forests and for explaining what absorbs 2 billion tons of missing carbon each year. Humans release about 7 billion tons of carbon annually, mostly in the form of carbon dioxide. Of that, 3 billion tons end up in the atmosphere and 2 billion tons in the ocean. It's unclear where the remaining 2 billion tons of carbon go, although scientists suspect forests capture and store much of it as biomass through photosynthesis. The new forest height map is a step toward a global map of all above-ground biomass. Sassan Saatchi, senior scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., already has started combining the height data with forest inventories to create biomass maps for tropical forests. Global biomass inventories will eventually be used to improve climate models and guide policymakers on carbon management strategies. The next generation lidar measurements of forests and biomass, which will improve the detail of the map considerably, could come from a planned NASA satellite mission, called the Deformation, Ecosystem Structure and Dynamics of Ice project. It is slated to launch no earlier than 2017. For images and additional information about the map, visit: http://www.nasa.gov/topics/earth/features/forest-height-map.html
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RELEASE: 10-197
NASA'S KEPLER MISSION DISCOVERS TWO PLANETS TRANSITING SAME STAR
WASHINGTON -- NASA's Kepler spacecraft has discovered the first confirmed planetary system with more than one planet crossing in front of, or transiting, the same star. The transit signatures of two distinct planets were seen in the data for the sun-like star designated Kepler-9. The planets were named Kepler-9b and 9c. The discovery incorporates seven months of observations of more than 156,000 stars as part of an ongoing search for Earth-sized planets outside our solar system. The findings will be published in Thursday's issue of the journal Science. Kepler's ultra-precise camera measures tiny decreases in the stars' brightness that occur when a planet transits them. The size of the planet can be derived from these temporary dips. The distance of the planet from the star can be calculated by measuring the time between successive dips as the planet orbits the star. Small variations in the regularity of these dips can be used to determine the masses of planets and detect other non-transiting planets in the system. In June, mission scientists submitted findings for peer review that identified more than 700 planet candidates in the first 43 days of Kepler data. The data included five additional candidate systems that appear to exhibit more than one transiting planet. The Kepler team recently identified a sixth target exhibiting multiple transits and accumulated enough follow-up data to confirm this multi-planet system. "Kepler's high quality data and round-the-clock coverage of transiting objects enable a whole host of unique measurements to be made of the parent stars and their planetary systems, said Doug Hudgins, the Kepler program scientist at NASA Headquarters in Washington. Scientists refined the estimates of the masses of the planets using observations from the W.M. Keck Observatory in Hawaii. The observations show Kepler-9b is the larger of the two planets, and both have masses similar to but less than Saturn. Kepler-9b lies closest to the star with an orbit of about 19 days, while Kepler-9c has an orbit of about 38 days. By observing several transits by each planet over the seven months of data, the time between successive transits could be analyzed. "This discovery is the first clear detection of significant changes in the intervals from one planetary transit to the next, what we call transit timing variations, said Matthew Holman, a Kepler mission scientist from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. This is evidence of the gravitational interaction between the two planets as seen by the Kepler spacecraft. In addition to the two confirmed giant planets, Kepler scientists also have identified what appears to be a third, much smaller transit signature in the observations of Kepler-9. That signature is consistent with the transits of a super-Earth-sized planet about 1.5 times the radius of Earth in a scorching, near-sun 1.6 day-orbit. Additional observations are required to determine whether this signal is indeed a planet or an astronomical phenomenon that mimics the appearance of a transit. NASA's Ames Research Center in Moffett Field, Calif., manages Kepler's ground system development, mission operations and science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, Calif., managed Kepler mission development. Ball Aerospace and Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. The Space Telescope Science Institute in Baltimore archives, hosts and distributes the Kepler science data.
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MEDIA ADVISORY: M10-088
NASA BRIEFS MEDIA ABOUT FIRST ARCTIC OCEANOGRAPHIC VOYAGE
WASHINGTON -- NASA will hold a media teleconference at 1 p.m. EDT on Tuesday, June 8 to preview the agency's first dedicated oceanographic research voyage. During the mission, scientists will study changing Arctic climate and ice conditions affecting ocean ecosystems. The Impacts of Climate on Ecosystems and Chemistry of the Arctic Pacific Environment mission, or ICESCAPE, will investigate how climate change in the Arctic may be altering the ocean's ability to absorb carbon from the atmosphere. The voyage will collect critical observations to compare to NASA's satellite views of ocean biology and sea ice. The data will improve scientists' understanding of this key component of Earth's climate system. The five-week voyage begins June 15, departing from Dutch Harbor, Alaska, on the U.S. Coast Guard icebreaker Healy. The ship will sail through the Bering Strait into the Chukchi and Beaufort seas off the northern coast of Alaska. More than 40 scientists will use an array of instruments to sample the physical and chemical characteristics of the ocean and sea ice, as well as the biological characteristics of the microscopic plant and animal life that regulate the flow of carbon into and out of the sea. A second voyage is planned for 2011. The teleconference participants are: - Paula Bontempi, ocean biology and biogeochemistry program manager, NASA Headquarters, Washington - Kevin Arrigo, ICESCAPE chief scientist, Stanford University, Palo Alto, Calif. - Don Perovich, ICESCAPE co-chief scientist, U. S. Army Engineer Research and Development Center Cold Regions Research and Engineering Laboratory, Hanover, N.H. To participate in the teleconference, reporters must contact Steve Cole at 202-358-0918 or stephen.e.cole@nasa.gov for dial-in instructions. Audio of the teleconference will be streamed live on NASA's Web site at: http://www.nasa.gov/newsaudio
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