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© Clipart.com © Swamp Gas from Outer Space! big surprise. The planet contained one of the building blocks of life—a chemical called methane! JULY 2008: Is there life on other planets? Early this year, astronomers found an exciting clue to this mystery. The scientists pointed the Hubble Space Telescope at a recently discovered planet 63 light years from Earth. The planet is called HD 189733b. As this Jupiter-sized world passed in front of its star, its atmosphere blocked some of the star’s light. Scientists could “read” this light to tell which chemicals exist on the planet. The scientists got a What’s so big about methane? Methane is an organic compound, a chemical that contains carbon and often comes from living things. Organic compounds make up the bulk of life, including you and me. This is the first time an organic compound has been found outside our solar system. © Photos.com © Corbis, Royalty-free, Steve Nagy By Kate Follett © iStockphoto, Taily ph ck a division of Learning A-Z © iStockphoto, JC Photography Scientists use special tricks to spot extrasolar planets. As a planet orbits, its gravity pulls the star in little circles. Scientists can spot this movement with telescopes. Some planets pass in front of their stars as they orbit. This blocks some of the star’s light, making it look dimmer. These changes in faraway stars are very tiny. But we’re finding more extrasolar planets every year! What makes a compound organic? Organic compounds contain er h carbon. This is why people say that living things sc on Earth are “carbon-based.” But maybe life on other planets is made of totally different stuff than life on Earth! © iS to © Learning A–Z, Inc. All rights reserved. Photos.com presented by First, extrasolar planets are extremely far away, so they are hard to see even with telescopes. Second, planets do not give off their own light, so they don’t show up against the blackness of space. Third, planets orbit, or move in a circle, around stars. Stars give off very bright light, which makes it almost impossible to see nearby objects. It’s like trying to follow a golf ball in front of the Sun, only trillions of miles away! oto, Chris D a t.com pa r Cli All known extrasolar planets, or planets outside our solar system, were found in just the last fifteen years. Why is finding extrasolar planets so hard? © Search for the Invisible Planets See Swamp Gas From Outer Space! on page 2 4 www.sciencea-z.com 1 So does this mean there are swamps, garbage dumps, and stinky animals on HD 189733b? Probably not. For one thing, the planet is very close to its star, making it way too hot for life as we know it. Also, methane can come from non-living things, such as volcanoes. But scientists hope they will find methane and other organic compounds on faraway planets that are more like Earth. They are excited to know that the building blocks of life exist outside our solar system. © Learning A–Z, Inc. All rights reserved. 2 Anaerobic microbes What would living things look like on an alien world? How would they survive? © Clipart.com Phoenix Lander This summer NASA sent a robot called the Phoenix Lander to Mars to discover whether liquid water ever flowed on the planet’s surface. Previous satellites had already revealed a large ice cap at Mars’s north pole and scientists believed that there was ice just under the soil, elsewhere. The Phoenix Lander arrived on Mars on May 25, 2008 after a nine-month journey, and began testing the soil. It found water ice just beneath the surface! If this ice was ever liquid, it’s possible that living organisms once thrived on Mars. The Lander will keep testing to find out. 3 © NASA.gov Anaerobic comes from the Greek words an (without), aero (air), and bios (life), meaning “without the air of life” or “without oxygen.” The word aerobic means “with oxygen.” So when you do aerobic exercises, you huff and puff! Write About This! © Photo Researchers, Inc., Eye of Science © Clipart.com way or another, most methane on Earth today comes from living or once-living things. © Clipart.com Methane is very common on Earth. It is found in natural gas, which formed when ancient plant and animal matter got squeezed inside Earth’s crust. Methane is also found in swamps, landfills, and other places where things decompose, or rot. Special organisms called anaerobic microorganisms (or tiny organisms that live without oxygen) break down plant and animal matter and give off methane. Anaerobic microorganisms even live inside some animals, such as cows. They help the animal break down its food, and they release methane gas. In one Methane traps heat in Earth’s atmosphere. What’s one big source of methane? Cow burps! Humans raise billions of cows for meat and milk, and their digestive gases pile up in the atmosphere. Some scientists are looking for ways to make cows less gassy in order to fight climate change. © iStockphoto, Clee Villasor Continued from page 1 © iStockphoto, Jan Brons Swamp Gas From Outer Space! www.sciencea-z.com