TOP 100 CAMPING SITES
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| Our Planet's Leaky Atmosphere One of the most remarkable features of the solar system is the variety of planetary atmospheres. Earth and Venus are of comparable size and mass, yet the surface of Venus bakes at 460 degrees Celsius under an ocean of carbon dioxide that bears down with the weight of a kilometer of water. Callisto and Titan--planet-size moons of Jupiter and Saturn, respectively--are nearly the same size, yet Titan has a nitrogen-rich atmosphere thicker than our own, whereas Callisto is essentially airless. What causes such extremes? If we knew, it would help explain why Earth teems with life while its planetary siblings appear to be dead. Knowing how atmospheres evolve is also essential to determining which planets beyond our solar system might be habitable.A planet can acquire a gaseous cloak in many ways: it can release vapors from its interior, it can capture volatile materials from comets and asteroids when they strike, and its gravity can pull in gases from interplanetary space. But planetary scientists have begun to appreciate that the escape of gases plays as big a role as the supply. Although Earth’s atmosphere may seem as permanent as the rocks, it gradually leaks back into space. The loss rate is currently tiny, only about three kilograms of hydrogen and 50 grams of helium (the two lightest gases) per second, but even that trickle can be significant over geologic time, and the rate was probably once much higher. As Benjamin Franklin wrote, “A small leak can sink a great ship.” The atmospheres of terrestrial planets and outer-planet satellites we see today are like the ruins of medieval castles--remnants of riches that have been subject to histories of plunder and decay. The atmospheres of smaller bodies are more like crude forts, poorly defended and extremely vulnerable. [More] rss.sciam.com |
5 Steps to Clean Up Air Pollution Even as the U.S. explores the complex challenges of global warming, air pollution remains widespread and dangerous. Millions of Americans live in areas that have recognized air pollution problems. Grave health effects--including death--are all too common. And the threat is not just to people: dirty air sickens and kills plants and animals and creates ugly haze that obscures spectacular views.Five policy changes could make the air we breathe cleaner and healthier. The American Lung Association and other public health and environmental organizations recommend these steps as the core of a clean air agenda for the nation: [More] rss.sciam.com |
Global Warming Beliefs [Below is the original script. But a few changes may have been made during the recording of this audio podcast.]Here’s one of the confusing issues regarding global warming: After all the data we’ve collected so far how can we still have such wide variety in outlooks for our future? [More] rss.sciam.com |
Critically endangered Angolan antelope gets a second chance Travel to the African nation of Angola and you'll see representations of the giant sable antelope ( Hippotragus niger variani ) everywhere you turn: on the country's currency, on stamps, and on company logos. But unless you look really hard, you probably won't find any actual giant sable antelopes. Fewer than 100 of the iconic animals are believed to exist following the devastation of Angola's bloody 27-year civil war. Now a new project hopes to reverse that and create some hope for this critically endangered species. [More] rss.sciam.com |
Risk-Taking Teens Have More Mature Brains Editor's note: The orignal online version of this story was previously posted. We often hear that teens are irresponsible because their brains are immature. But, contradicting that idea, teen turmoil is completely absent in more than 100 cultures around the world [see “ The Myth of the Teen Brain ,” by Robert Epstein; Scientific American Mind , April/May 2007]. Nevertheless, neuroscience studies do indeed suggest that the gray matter in the frontal cortex of teens, as compared with adults, is not fully developed. [More] rss.sciam.com |