A Satellite to Track a Gas
1On a Saturday at a space agency's visitor center, a group of sixth graders worked as a mission planning team. Their task was to help plan a new satellite that would measure methane in the air from orbit. Mission scientist Dr. Sunniva Haugland led the briefing. The mission is made up, but the data she shared are based on real measurements, rounded.
2Earth's average surface temperature has risen by about 1 °C since the late 1800s. Gases that absorb energy given off by Earth's surface and send some of it back down are called greenhouse gases. Carbon dioxide (CO₂) is the best known, but methane is another. There is far less methane in the air than CO₂, yet each methane molecule absorbs much more energy than a CO₂ molecule does. Methane does not last as long, though: most of it breaks down in the air within about ten years.
3Methane comes from both natural processes and human activities. Microbes that live where there is little oxygen give off methane. They live in wetland mud, in the stomachs of cattle and other livestock, in flooded rice fields and in buried garbage at landfills. Methane also leaks from coal mines, oil wells and natural gas pipelines. Termites, lakes and wild animals add a smaller natural amount.
4Dr. Haugland showed the team measurements from ground stations around the world (Table 1) and scientists' estimates of how much methane each source releases each year (the graph). "A satellite gives us numbers," she said. "Your job is to ask the questions those numbers should answer." Team members Kofi Asante and Mireille Dubois took notes.