The vast majority of grasses retain their lifeless leaves, raising the question of why they keep dead weight that could drain their productivity. To find out, scientists at the University of Buenos Aires removed dead leaves from grass in the Argentine pampas, where cattle graze. In the absence of cows, the pruning promoted grass growth, but in the presence of bovines, those grasses were grazed on more so than intact ones, resulting in less growth. The findings, published online January 15 by Oikos, suggest that dead leaves act as a defense against herbivores. —Charles Q. Choi


When the threat of lung cancer and wrinkles doesn't work, maybe $750 will. Cigarette smokers who received money to quit were 2.9 times more likely to break the habit than those who just tried to do it for their health. Participants were offered $100 to complete a smoking cessation program, $250 for quitting within the first six months and $400 for keeping clean an additional six months. Even after that, those who got the cash were 2.6 times more likely to have stayed smoke-free. The study appears in the February 11 New England Journal of Medicine. —Coco Ballantyne


In an orbital traffic accident 490 miles above Siberia, a Russian satellite and a commercial satellite owned by U.S. communications firm Iridium collided in February. It wasn't exactly unexpected, given the number of objects in orbit—the past 20 years has seen three other accidents, but they were minor, only producing a few pieces of debris. This latest impact, however, yielded hundreds, and some pieces have drifted down to the altitude of the International Space Station, posing a small but still real hazard. —John Matson