Brittle bones in space

Astronauts travelling to the moon and beyond face an unexpectedly large risk of bone loss as a result of cosmic radiation, new research on mice suggests.

Astronauts travelling to the moon and beyond face an unexpectedly large risk of bone loss as a result of cosmic radiation, new research on mice suggests. Space scientists have long known that weightlessness causes atrophy of bones and muscles, and researchers had suspected that radiation could also have an effect. But the mouse experiment found that even limited exposure to certain kinds of radiation caused a loss of 39 percent of the spongy portion of the inner bone. 8216;8216;We were really surprised to find that degree of bone loss,8217;8217; said lead researcher Ted A. Bateman of Clemson University, whose findings appear in the online version of the Journal of Applied Physiology. He said that the radiation primarily degraded the spongy inner 8216;8216;trabecular8217;8217; portion of the bone rather than the hard outer 8216;8216;cortical8217;8217; area. Bateman said that the results of a mouse study cannot be directly applied to people but that they are consistent with research findings that women who receive radiation treatment for cancer are substantially more likely to experience fractures because of bone loss. 8216;8216;I think this means that the combination of radiation and weightlessness pose some real biomedical problems for humans living for long periods in space,8217;8217; he said. While astronauts have experienced some bone loss, it has not been dramatic. Bateman said this may be because, except for the moon missions, the astronauts remained inside Earth8217;s magnetic field, which protects against the cosmic radiation that is likely to be most damaging8212;protons and heavy ions. 8212;LAT-WP

The physics of geological art

At Mammoth Hot Springs, in Yellowstone National Park, the mineral-rich waters flow over a surreal landscape of stepped terraces and ponds. Geologists have long been at a loss to explain the rocks8217; unusual shapes, but physicists at the University of Illinois at Urbana-Champaign say they have figured out the answer. Unlike most water-washed surfaces, the primary geological process shaping the Mammoth Hot Springs landscape is not erosion. The rocks there are actually growing8212;at the rate of one to five millimeters a day8212;as calcium carbonate in the water precipitates to form the mineral travertine. The key to understanding the process, the physicists say, is ignoring the details of mineralogy and geochemistry.

The shapes, the researchers, could be explained by general equations, not geology. The main factors are the flow of water and the material it deposits. The minerals grow into a bump and then a dam, which alters the flow. When the scientists wrote down the equations and ran computer programs mimicking the process, the result was artificial landscapes that looked remarkably like Mammoth Hot Springs. 8212;NYT

Stirring up soil trouble

Modern farmers aren8217;t the only ones who have problems keeping the soil in good shape. Research on the island of Maui suggests that the Polynesians who settled Hawaii had trouble, too. Anthony Hartshorn of the University of California, Santa Barbara, and colleagues looked at the effect on soil nutrients of cultivation of taro and sweet potato on the slopes of Haleakala volcano. As the Polynesian settlers expanded into the drier, leeward parts of the islands beginning in the 1400s, they brought these crops with them. Archaeological evidence shows that in these drier regions, the crops were grown on a portion of volcanic slopes where conditions were right.

These slopes had a zone of highly stratified soil about three feet thick over lava bedrock, consisting of a top layer of ash, an intermediate layer of larger nutrient-rich cinders and another ash layer that served as a water reservoir on the bottom. To reach this bottom layer to quench their crops8217; thirst, the early Hawaiians dug through the surface ash and cinder layers with a stick, rotating it to create a cone-shaped hole for planting. That way the roots could reach the water below.

But the researchers report this week in The Proceedings of the National Academy of Sciences that this practice resulted in the depletion of calcium, magnesium and other nutrients over time. Their experiments showed that digging crushed some of the cinders, increasing their surface area, and also mixed cinders with moist ash. Both conditions led to increased leaching of nutrients from the cinders.8212;NYT