ON THE 40TH anniversary of the lunar landing, the planet Jupiter was hit by a milewide asteroid, leaving a large black scar roughly the size of the Pacific Ocean on Jupiter's surface. The collision, which was discovered by an Australian amateur astronomer and came as a surprise to scientists, is a reminder that the universe is a dangerous place. Jupiter, the fifth planet from the sun, is 318 times larger than Earth and acts as a stellar vacuum cleaner, with a gravitational pull that attracts most of the asteroids that pass by. In March, however, Earth faced a close call as an asteroid named 2009 DD45 passed within 45,000 miles, mere inches on a cosmic scale. Its trajectory was discovered only three days in advance. The most famous recent example of Earth being hit by a so-called NEO (near-Earth object) is the 1908 Tunguska Event, when an asteroid with a diameter of 45 to 70 meters exploded over Tunguska in Siberia, unleashing the energy of 10 megatons of TNT, equivalent to a hydrogen bomb, and leveling about 100 million trees over an area of 800 square miles. If it had struck four hours later, St. Petersburg would have been wiped out. So far, some 6,200 NEOs have been discovered in our solar system, of which 1,000 are deemed "potentially hazardous," and 784 are registered as more than a half-mile wide. NASA's Jet Propulsion Laboratory keeps a running tally of NEOs at neo.jpl.nasa.gov/stats/. Scientists believe there are plenty of similar NEOs that have yet to be discovered, and as the Jupiter collision proved, they might not be discovered before it is too late. At present, astronomers are tracking the asteroid 99942 Apophis, which has a slight chance of striking Earth in April 2036. Though it is reasonably small by asteroid standards — about 300 meters across — a collision would unleash a force about 60,000 times that of the Hiroshima nuclear bomb, enough to destroy an area the size of France.

For more information, visit http://www.theatlantic.com/doc/200806/asteroids.

EVEN THOUGH THE United States has not signed the international environmental treaty known as the Kyoto Protocol, emissions here have been better controlled than in other countries. According to the U.S. Energy Information Administration, carbon dioxide emissions from the burning of fossils fuels only increased by 0.7 percent in the United States from 2000 to 2006, compared to 27.7 percent in India, 45.8 percent in Malaysia and 103 percent in China. Overall, emissions in Europe (up 4.9 percent) and Asia (up 52.3 percent) followed suit. By 2030, India and China are expected to account for 34 percent of the world's emissions, as growing populations move out of poverty and join the middle-class life enjoyed on average in richer, industrialized nations, thereby increasing their demand for energy. According to Drew Thornley, author of the new report "Energy & the Environment: Myths and Facts," international environmental treaties that penalize conventional energy sources make little sense if other countries swamp American reductions. The same goes for ambitious political initiatives. Rather, it would seem, we do better than others without adopting an international carbon-cutting regime.

For more information, visit www.american.com/archive/2009/june/emissions-control-myths-and-realities.

MORE THAN 55 million years ago, an extremely significant and rapid change in climate, referred to as the Paleocene-Eocene Thermal Maximum, occurred during the Cenozoic Era. Temperatures increased between 5 and 9 degrees Celsius (between 10 and 18 degrees Fahrenheit), at a time when the world was warmer than it is now and held no surface ice. Researchers at the University of Hawaii at Manoa have released a study in "Nature Geoscience" that indicates global warming cannot be explained solely by a surge in carbon dioxide levels. By studying sediment cores from seabeds around the globe, the scientists have come to the conclusion that there were, in fact, additional factors. An initial trigger is believed to have been involved, such as a deep ocean warming that caused a cataclysmic release of methane from hydrate deposits under the sea bed. Much of the methane oxidizes into CO2 when released from hydrate deposits. It is estimated that the amount of CO2 released during the Paleocene-Eocene event was about 11 trillion tons, released over several thousand years, which led to a 70 percent rise in atmospheric CO2 levels from pre-event levels. But only about 1 to 3.5 degrees Celsius of the rise in temperature is explained by this event. The study suggests that there might be atmospheric or oceanic processes yet unknown that could have accelerated the warming. Some estimate CO2 levels could increase by 70 percent in this century, much faster than during the Paleocene-Eocene Thermal Maximum. The researchers hope the unknown processes can be identified to estimate their future potential effect on climate change.

For more information, visit http://in.reuters.com/article/worldNews/idINIndia-41050320090715?sp=true.