CASH FOR CAULKERS: President Obama is visiting Savannah, Ga., today, unveiling the details of his $6 billion proposal to give cash rebates to consumers who make energy-saving home improvements. Officially named the Home Star Program but widely dubbed "cash for caulkers," the plan would let homeowners collect on-the-spot rebates up to $3,000 when they buy insulation, water heaters and other equipment to help their homes use energy more efficiently. While it still needs approval from Congress, the White House is hoping the plan can carry over some of the success of last year's $3 billion "cash for clunkers" program, which rewarded drivers for trading in older vehicles for more fuel-efficient ones. The Obama administration expects about 2 to 3 million households to participate in the Home Star program, with each saving about $200 to $500 a year in energy costs. (Sources: Associated Press, Reuters, Wall Street Journal)

AXIS UPHEAVAL: It's been a crazy winter, but at least the days are starting to get longer again. Or are they? Scientists at NASA say the magnitude-8.8 earthquake that hit Chile on Saturday shifted the Earth's axis about 3 inches, permanently shortening the length of a day. From now on, every day on Earth will be 1.26 microseconds shorter, according to NASA's preliminary calculations, because the axis shift has redistributed the planet's mass, much like a figure skater who pulls in her arms to spin more quickly. When the Earth rotates more quickly, days go by faster — although the change won't be noticeable, since a microsecond is one-millionth of a second. The length of a day last changed in 2004, when the magnitude-9.1 Sumatran quake shortened it by 6.8 microseconds. (Sources: CNN, NASA)

AMBIGUOUS AMPHIBIANS: The common weed killer called atrazine can chemically "castrate" male frogs, a new study has found, feminizing them so completely that they can even mate with other male frogs and lay viable eggs. Atrazine is used widely on U.S. cornfields, but has been implicated in several recent studies of tinkering with animals' hormones, and blamed for creating males with female behaviors or body parts. But the new study, published online in the Proceedings of the National Academy of Sciences, seems to document an even more dramatic transformation: Some male frogs became fully female, except for their genes, allowing them to mate with other males and carry eggs. The researchers say this may be because atrazine is absorbed by the amphibians' skin and produces an enzyme that converts testosterone into estrogen — adding that it could have similar effects in humans. "It's a chemical ... that causes hormone havoc," says the study's lead author. "You need to look at things that are affecting wildlife, and realize that, biologically, we're not that different." (Sources: Washington Post, ScienceDaily)

MOON MOISTURE: An Indian spacecraft carrying U.S. equipment has found millions of tons of frozen water on the moon's north pole, a resource that could possibly one day be used to generate oxygen or sustain a moon base. NASA's Mini-SAR used radio waves to measure the moon's surface roughness, discovering 40 craters, ranging from 1 to 9 miles in diameter, packed with thick pockets of ice. NASA scientists say the craters may contain at least 600 million tons of water ice, which would have to be relatively pure and at least several feet thick to produce the observed measurements. Their findings follow other projects in recent months — including one that involved smashing a spacecraft into the lunar surface to kick up a cloud of ice — that have revealed a much more dynamic, and moist, moon than scientists once believed. "The results from these missions ... are totally revolutionizing our view of the moon," says Paul Spudis, of NASA's Lunar and Planetary Institute in Houston, adding that if the newly discovered water were an equivalent amount of rocket fuel, it would be enough to launch one shuttle every day for 2,200 years. (Sources: BBC News, Wired)

CULTURE OF LIFE: It was long believed that culture had insulated humans against natural selection, with society's safety net shielding us from the evolutionary forces that kill off the weaker members of other species. But it has become increasingly clear, the New York Times reports today, that culture is actually a powerful contributor to natural selection, as cultural changes often set the stage for genetic changes down the road. Lactose tolerance is one example — most people and other mammal switch off their gene that digests lactose once they're weaned, but in the descendants of ancient cattle-raising cultures, the gene now stays active in adulthood. That's why many Northern Europeans and Kenyan herdsmen are lactose-tolerant while most of the world isn't; drinking milk must have offered such an evolutionary advantage in those societies that people who could digest it produced more offspring than those who couldn't. Of the roughly 2,000 genes in the human genome, scientists have determined that up to 10 percent are currently under selective pressure, meaning we can watch ourselves evolve. (Source: New York Times)

Russell McLendon

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Photo (Obama on his "White House to Main Street" tour in Ohio, Jan. 22): Charles Dharapak/AP

Photo (Earth and sun): NASA

Photo (African clawed frogs): Muffet/Flickr

Photo (moon): NASA

Photo (milk): Jupiter Images