From: Kathleen M. Wong, California Academy of Sciences
Published January 21, 2005 12:00 AM

Space Mission Lands On Titan, and Other Stories

Space Mission Lands On Titan


Humanity got a glimpse of a strange new world January 14 when the European Space Agency probe Huygens landed on Saturn's moon Titan. Its arrival reveals a sherbet-orange landscape with snaking river channels and rocky sediments. After a seven-year trip into the Saturn system atop NASA's Cassini space probe, Huygens spent 2.5 hours plunging through Titan's atmosphere taking pictures all the way. The probe continued to operate for more than an hour after landing just as designed. It has sent back a torrent of data that scientists are still analyzing. Early results demonstrate that the thick methane and nitrogen smog hiding Titan from earthly view clears up toward the surface. Hugyens' chemical detectors found methane, ethane, acetylene and other hydrocarbons evaporating around the probe. Scientists believe these hydrocarbons may have carved out the river channels and have pooled in what appears to be a nearby sea. Huygens landed on a hard, frozen surface crust that gave way to a material similar in texture to wet sand. Ambient temperatures averaged a frigid -180 degrees Celsius. Titan is the most distant world ever visited by spacecraft. Scientists believe conditions on Titan may resemble those on early Earth.


Dinosaur On Early Mammal's Menu


The world's first mammals were ratlike creatures that, in the age of the dinosaurs, could do little more than take cover and quail. Now researchers at the American Museum of Natural History in New York and the Chinese Academy of Sciences in Beijing have found two early mammals that turned the tables on their giant overlords. In the famous Liaonang fossil beds of northern China, they found a 130-million-year-old mammal fossil with bits of baby dinosaur in its stomach. Known as Repenomamus robustus, the mammal had devoured a juvenile parrot-faced dinosaur--the first evidence that early mammals ate vertebrate prey. The second specimen, dubbed Repenomamus giganticus, is even more impressive. A short legged, long-bodied creature about the size of a basset hound, it was roughly twice the size of the next-largest contemporary mammal and possessed sharp teeth for seizing and slashing prey. At about 30 pounds, it was large enough to hunt many dinosaur species. Both early mammals had limbs that protruded laterally from their bodies in a manner similar to lizards; they could have waddled and stood on their hind legs, but were not runners.


Human Ancestors Walked Upright Early On


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Tiny fragments of bone unearthed in Ethiopia indicate early hominids walked upright on two feet 4.5 million years ago. The bits of teeth, jaw, and hands, and feet, belonged to nine individual Ardipithecus ramidus specimens. The foot, or phalanx, bones demonstrate that the creature must have walked upright. It had diamond-shaped teeth rather than the v-shaped canines of chimpanzees, but probably looked more like apes than modern people. Sileshi Semaw of Indiana University in Bloomington and colleagues dated the bones by analyzing volcanic sediments found nearby. They ranged from 4.32 to 5.51 million years old. Genetic studies indicate a common ancestor of humans and apes existed about 6 million years ago. The oldest A. ramidus specimen found so far has been dated to 5.2 million years old, making the species a strong contender to be the oldest modern human ancestor yet identified. The Afar region in which the fossils were found is desert today. But A. ramidus seems to have lived amid a far lusher landscape that included springs and swamps populated by monkeys, mole rats, and grazers similar to cattle. Scientists hope to learn more about ancient habitat conditions at the site to determine whether early hominids might have begun walking upright to better see predators or prey across the savannah. The find was described in the journal Nature.


Invaders Can Break An Ecosystem's Back


The arrival of the right invasive species can be enough to send embattled native populations belly up. The research, by Ted Grosholz of the University of California, Davis, suggests ecosystems in California's Bodega Bay are headed for "invasional meltdown." For the past 45 years or so, the native Nutricola confusa clam has been holding its own against the eastern gem clam (Gemma gemma) from the Atlantic seaboard. Gem clams were present, but not plentiful, until about 1994. That year marked the arrival of the European green crab, delivered to the bay from Asia. Grosholz found that in laboratory experiments, the crabs on average ate native clams twice as often as gem clams, probably because the natives are larger. He reports in the Proceedings of the National Academy of Sciences that by decimating native clam populations so rapidly, the crab has dramatically worsened the spread of gem clam populations. The findings suggests that the addition of more invasive species can cause whole ecosystems to collapse like a house of cards.


Extrasolar Planet Caught In Telescope Sights


After deducing the existence of dozens of extrasolar planets, scientists have finally caught their first visual glimpse of a distant world. Typically, scientists detect distant planets by observing wobbles in the orbits of stars. But a series of happy coincidences helped the Glenn Schneider of the University of Arizona at Tucson and colleagues make their discovery. For one thing, the planet the planet is located unusually far from its star--more than a third farther than Pluto is from our sun. That distance helped astronomers distinguish the two bodies. Secondly, the planet's sun is a brown dwarf, a dim type of star unable to obscure the planet in its glare. Finally, the planet itself is enormous, around five times the size of Jupiter. The astronomers found it last spring by analyzing emissions of infrared light using the Very Large Telescope in Chile. Scientists are puzzled over why the planet is located so far from its star; they speculate that it may have formed closer in and migrated outward. The discovery was announced at a meeting of the American Astronomical Society in San Diego, California.


Tsunami Hurt Corals, But Mangroves Buffered Wave Blows


The tsunami that ravaged communities around the Indian Ocean this month did not spare local wildlife. As human deaths approach a quarter of a million, scientists are realizing that the coral reefs that attracted tourists and fed local people are in bad shape. Coral reefs are being smothered by sediments streaming into coastal waters from denuded shorelines. Without sunlight, coral are unable to photosynthesize. To make matters worse, the force of the waves has broken off large chunks of corals. The loss of coral could hit local marine ecosystems hard, as the living reefs provide both food and habitat to fish, sea turtles, dugongs, and dozens of other species. Wildlife on land seems to have fared much better. Rangers have reporting finding no dead elephants, water buffaloes, or other large animals anywhere in the devastation. Some naturalists reported seeing many lizards and snakes in trees during the flooding. Scientists say keen senses, such as elephants' ability to sense the low rumbles of infrasound emitted by the tsunami, may have helped them escape. The presence of mangrove forests near wildlife reserves probably also helped dampen the force of the water. Indonesia has promised to replant mangroves previously cleared for aquaculture pens.


Dolphins Hold Down Hunting Jobs


Individual dolphins will perform the same job in a group hunt time after time, scientists have found. The discovery, published in the Proceedings of the Royal Society of London B, shows that these marine mammals practice role specialization. Stefanie Gazda, now with the New England Aquarium in Boston, and colleagues observed two packs of bottlenose dolphins on 60 group hunts each off the coast of Florida. One pod had three members while the other ranged from two to six dolphins. The researchers found that the same dolphin in each pack always drove fish toward its waiting comrades. Such specialized hunting roles have only been seen before in African lionesses, where several lions will herd prey toward an ambusher. In the case of the dolphins, the driver always snapped up more fish than its partners, raising the question of why the other dolphins never traded jobs. The researchers suggest that the driver may be particularly talented at its role, resulting in a better catch for the whole pack. Alternatively, packs might be made up of family groups where the driver also serves as the group leader.


Related Links:


Space Mission Lands On Titan: San Francisco Chronicle / Los Angeles Times / BBC
Dinosaur On Early Mammal's Menu: New York Times / Scientific American / National Geographic
Human Ancestors Walked Upright Early On: BBC / Discovery.com (Agence Fance Presse)
Invaders Can Break An Ecosystem's Back: San Francisco Chronicle (scroll down for story)
Extrasolar Planet Caught In Telescope Sights: New Scientist / news@nature.com
Tsunami Hurt Corals, But Mangroves Buffered Wave Blows: Yahoo Daily News (Associated Press) / Yahoo Daily News (Reuters)
Dolphins Hold Down Hunting Jobs: news@nature.com


Source: California Academy of Sciences


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