On the horizon

Wanted: spacedust screeners

Astronomers are hunting for interstellar dust grains, and they want your help.

This week, scientists launched their "stardust@home" project. It's an online effort to identify perhaps 50 grains of interstellar dust from within 40,000 "virtual" microscope slides that can be viewed on an Internet browser. The slides show slices of a substance called aerogel, which NASA used as a cosmic dust mop aboard its Stardust spacecraft. The dust grains are embedded in some of these slices. The Stardust mission returned samples of material the sun emits as "solar wind." It also aimed to pick up rare grains of interstellar dust formed through enormous stellar explosions called supernovae. These explosions seed the universe with many of the chemical elements heavier than hydrogen or helium. These heavy elements form in the precursor star before it blows up.

Scientists at the University of California at Berkeley have set up an online tutorial showing what to look for and a quick qualification quiz for would-be participants. So far, more than 115,000 people have volunteered. But researchers are looking for more participants to speed up the screening process. For more information, visit http://stardustathome.ssl.berkeley.edu

Where bees buzz, color counts

When bees zip among flowers for nectar, they may be hunting for warmth as well as a quick sip at the blossom. Surprisingly, new research suggests, bees can learn to use a flower's color as a cue to where the warmest flower is found. And the plants themselves may raise their internal thermostats to attract pollinators such as bees.

Flower temperatures vary, even within a plant species. And bees have long been known to detect colors. Recent research suggests that they are as adept at distinguishing colors as humans. Moreover, bees burn a lot of energy buzzing among blossoms. Bees wouldn't have to burn as much food to maintain their body temperature in warmer flowers, reasoned scientists from Cambridge University and the University of London.

So they set out to test whether bees can use flowers' colors to zero in on the warmest of them. They found that warmer nectar attracted more bees. They used fake pink and purple flowers and a nectar stand-in to establish that the bees could learn to use flower color to guide them to the warmest "nectar." Then they exposed the bees to flowers of the same color but with varying temperatures. The bees were as likely to land on one flower as another, despite the temperature differences. The results appear in Thursday's issue of Nature.

Microbe census surprises scientists

Microbes may be tiny, but biologists hold that they are the bedrock for life on Earth. They are thought to represent the planet's only life form for the first 80 percent of its history. Microbes have also helped shape the evolution of the planet's atmosphere and play a part in vital geological processes.

No wonder marine biologists are excited about initial results from the first census of microbial life in the ocean. Where scientists expected to find perhaps 1,000 to 3,000 different species in a quart of seawater, they found more than 20,000. The total number of species ultimately could range from 5 million to 10 million, according to Mitchell Sogin, director of the Marine Biological Laboratory in Woods Hole, Mass. Dr. Sogin is the lead author on the research paper announcing the results in this week's issue of the journal Proceedings of the National Academy of Sciences.

The 10-year effort began in 2000 and uses a new technique that requires only a small segment of a microbes's DNA to identify it. The most peculiar of these DNA "tags" come from organisms that appear to be extremely rare, leading researchers to dub them inhabitants of "rare biospheres."

"The detection of these previously overlooked microbes opens a world of new questions about their role in ecological processes and their evolutionary history," Sogin explains.

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