On the horizon

Probe added to moon water hunt

When NASA's unmanned Lunar Reconnaissance Orbiter heads to the moon in 2008, it will have a new companion.

This week the agency announced that another spacecraft will piggyback on the orbiter's rocket. The probe is designed to look for ice thought to lie just beneath the surface inside craters at the moon's north and south poles. An accessible water source would be highly prized at any future lunar outpost that NASA or any other space agency may plan. Among other uses, water can be broken down into hydrogen and oxygen and used as "home-grown" rocket fuel.

In 1999, NASA's Lunar Prospector mission found evidence that led scientists to believe that significant amounts of ice were at the poles. But when the craft plowed into the surface at the end of its mission, no ice was detected.

In the new mission, the rocket's final stage aims to strike a crater at the moon's south pole, where water is thought to hide. The hitchhiking craft will then swing through the plume of debris to hunt for water.

Next, the probe itself will be used as a second impactor. On Earth, astronomers will aim their telescopes at the plumes to look for signs of water.

One inhabitant of Jurassic Park that should have gotten some screen time: the humble ant.

While scientists have described 11,800 species of modern ants, the insects' evolutionary history is poorly known. New research suggests that the species of ants that plague today's picnics sprang from a common ancestor between 140 million and 168 million years ago - far earlier than previous estimates. But their diversity exploded 60 to 100 million years ago, according to a team led by Corrie Morea, with Harvard University's Museum of Comparative Zoology. The team suggests that ants were evolutionary underachievers until flowering plants and trees underwent an explosive expansion some 100 million years ago. The leaf litter gave ants more places to live. Plant nectars, as well as the rise of plant-eating insects, boosted their food supply.

The team traced the ant family tree by analyzing the DNA from 149 specimens from 19 of the 20 known living ant subfamilies. They also used 43 ant fossils to check the times when the subfamilies split from their ancestors. The results appear in the current issue of Science magazine.