On the horizon

More signs of water on Mars

Researchers scouring images of Mars' surface say they have found evidence of ancient heavy rainfall or sudden snow melt on the red planet.

A team from the Smithsonian Air and Space Museum's Center for Planetary Studies and the University of Virginia discovered 21 river channels in valleys on the planet. The width of the channels provides clues for how much water flowed through them. On average, the channels are roughly the same size as river channels in dry regions on Earth that are etched by sudden downpours or snow melt.

The images, taken by the Mars Odyssey spacecraft currently orbiting the red planet, bring to 29 the number of river channels researchers have spotted. The team notes that it's likely the planet once had a climate similar to the desert in the southwestern United States, where long dry spells are punctuated with shorter periods of wet weather.

The value of Antarctica's ice

East Antarctica's vast ice sheet appears to be applying gentle brakes to sea-level rise. That's the conclusion a team at the University of Missouri (Columbia) has drawn after studying changes in the ice sheet's height. Using satellite data from 1992 to 2003, the team found that the ice sheet's interior was gaining mass at the rate of 45 billion tons a year. The group estimates that this growth would reduce sea levels by 0.18 millimeters (7/1000ths of an inch) a year, offsetting for now the effects of melting ice caps elsewhere.

The researchers note that the increase in mass closely follows increases in precipitation. They add that both results - more snow and thickening ice in the region - are consistent with projected effects of global warming. The group's results appear in the latest issue of the journal Science's online publication Science Express.

Tsunami footprints

Scientists continue to tally the effects of last December's devastating Sumatra-Andaman earthquake. The quake has left them "searching for words and tools to describe the enormity of the geological processes involved," writes University of Colorado geophysicist Roger Bilham, who summarizes the results from four research teams whose work appears in the latest edition of the journal Science.

The rupture along the southern portion of the plate boundary sped north at 5,000 miles per hour. By the time it reached the northern end of the rupture zone, it had slowed dramatically, taking more than a half hour to cover 8 to 22 yards. That slowdown avoided what could have been an even more devastating tsunami. The entire quake lasted 10 minutes.

The researchers estimate that changes in the height of the sea floor initially shifted 30 cubic kilometers (7.2 cubic miles) of water. The globe's sea level is now 0.1 millimeter higher, as a result of the sea-floor's displacement. The ensuing tsunami, which leveled coastal communities in its immediate path, eventually lapped at the shores of Antarctica and the east and west coasts of the Americas. If vertical or horizontal changes in the Earth's crust are measured down to the centimeter level, no spot on Earth remained unaffected, the research shows.

Inside scoop on a growth hormone

The inner workings of auxin, a key growth hormone used on farms and in the nurseries, have baffled scientists for decades. Now, two teams in the US and Europe have independently uncovered how this biological handyman performs its jobs - including acting as an herbicide, ripening fruit, and steering blossoms to face the sun.

They've discovered that auxin works in concert with a long-known cluster of proteins to serve as a biochemical key. In essence, the proteins "sense" auxin's presence. Together, they trigger the destruction of the biochemical barriers that silence genes controlling various aspects of plant development.

Scientists suggest that the discovery could lead to auxin-like compounds for agriculture that are less expensive, safer, and easier to make than current synthetic auxins, or that can be tailored to trigger specific responses in plants. The two teams - from Indiana University and universities in Britain and Sweden - reported their results in Thursday's issue of the journal Nature.

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