On the horizon

Mapping out Mars

New mineral maps of Mars are revealing that the planet has a more complex geological history than it's been given credit for - and this geology may still be evolving.

The evidence comes from the Mars Odyssey spacecraft, which has been scrutinizing the red planet's surface composition from orbit since February 2002. A research team has found a broad range of volcanic rock, from basic basalts to quartz-bearing rocks and granites. These underwent several episodes of remelting deep in the planet's interior over long periods of time. The surface remains dominated by basalt; the more varied rocks show up at highly localized sites.

The Mars Odyssey results would mirror those that might be taken from a spacecraft orbiting an Earth without oceans, says Arizona State University's Philip Christensen, who headed the research team. The maps are providing the broad geological context for current and future missions to Mars by robotic rovers. The results appear in Thursday's issue of the journal Nature.

Ecologists have seen how mankind's quest to hoist the biggest fish or bag the largest bighorn sheep have led to populations of smaller, less reproductively successful individuals. Now, they're seeing the same effect on rare plants. Heavy harvesting of the Himalayan snow lotus has stunted the size of later generations, report scientists from Washington University in St. Louis and the Missouri Botanical Gardens. This rapid evolutionary change could threaten the species' survival, they say.

The largest plants are prized, mostly as a folk medicine. The scientists compared plants in heavily harvested areas with the same species in protected areas and in herbariums around the world, where some specimens trace their lineage to the late 1870s. They also compared the snow lotus with a less intensively picked relative. Plants from heavily harvested areas averaged three to four inches shorter than those from areas where fewer plants are picked. This inadvertent "dwarfing" needs to be considered when planning conservation strategies, the scientists say. Their work appears in the current issue of the Proceedings of the National Academies of Science.

The bluebird of happiness is winging its way around conservationists these days. New experiments have shown that corridors linking habitats work - at least for bluebirds.

Researchers have long backed the use of corridors as a way to turn highly fragmented habitats into a relatively large one capable of supporting biodiversity among animals. While the idea seemed to make sense on the surface, few experiments have tested it.

So researchers from North Carolina State University and the University of Central Florida devised a test: Set up an experimental forest with a home base of bluebird habitat along with four other patches of the bird's habitat; link one patch to the home base with a corridor; equip another patch with two stunted corridors that don't connect to anything else; leave the remaining two patches without any corridors, and then see how the birds respond.

By watching the birds and tracking droppings "tagged" with fluorescent seeds from the birds' favorite wax myrtle bushes, the team found that the seeds were 37 percent more likely to appear in the patch linked to their home base than in the three other patches. Interestingly, the birds seemed to fly along the edges of the corridor, rather than down the middle - suggesting that a corridor with distinct edges may be more important for the birds than its width. The work appears in the current issue of the journal Science.

This has been a good breeding year for the critically endangered North Atlantic right whale, according to biologists with the National Oceanic and Atmospheric Administration. So far this year, biologists have sighted 28 unique mother-calf pairs. The most productive year on record is 2001, when researchers found 31 right-whale calves.

Between 325 and 350 right whales are known to exist. Populations of these mammals initially plummeted as a result of commercial whaling. More recently, collisions with ships and entanglement in fishing nets or their drag lines have inflicted further casualties.

Researchers will be watching to see how many of the youngsters survive to adulthood, when they can breed. Typically only about 25 percent of a season's calves survive, and females take 10 years to reach reproductive maturity.