Eastern roots A mix of anatomical traits on a 40,000-year-old partial human skeleton unearthed in China supported the controversial possibility of interbreeding among Stone Age Homo species (171: 211).
Early walkers New fossil finds showed that 1.77-million-year-old human ancestors trekked from Africa to Asia using legs, feet, and spines shaped much like ours, although they had small brains and apelike arms (172:179 *).
Researchers excavated a 4,600-year-old village in southern England that was inhabited by the same people who built nearby Stonehenge as a memorial to their dead (171: 67).
A coastal South African cave yielded evidence of surprisingly complex behaviors, including shellfish harvesting and pigment use, about 164,000 years ago (172: 243).
Pacific trips DNA extracted from a chicken bone found in Chile suggested that Polynesian seafarers brought poultry to South America by about 620 years ago (171: 356 *). Other evidence indicated that, roughly 1,000 years ago, Polynesians sailed canoes to Hawaii and back (172:198).
Chimp hunters Researchers for the first time observed wild chimpanzees, mainly females and youngsters, making and using tools for hunting small animals (171: 131 *). An excavation in western Africa revealed that a chimp stone age started at least 4,300 years ago (171: 99 *).
A new analysis of fossil teeth from the fossilized remains of a nearly 8-year-old child suggested that people evolved an extended childhood at least 160,000 years ago (171: 163).
Tree walking Field work in Indonesia demonstrated that orangutans at times walk upright much as people do, suggesting that an upright stance evolved in a common ancestor of all living apes (172: 72 *).
Tool time Primate and brain-scan studies converged on the notion that human tool use grew out of an evolutionarily ancient neural capacity for manipulating objects (171: 88).
Alien orbs Astronomers found what they are calling Earth's closest known analog outside the solar system, an object with an average temperature that may allow water to be liquid (171: 259 *). A newly discovered planet outside the solar system--an exoplanet--appeared to be Neptune-sized and composed mainly of water solidified under high pressure (171: 308 *). Researchers for the first time recorded the spectra of radiation emitted by two exoplanets (171: 115 *). They also discovered the largest--and lowest-density--exoplanet yet found (172: 174).
Blooming comets Flaunting a majestic tail over southern skies, Comet McNaught became the brightest comet in more than 40 years (171: 52). In late October, Comet 17P/Holmes suddenly burst into brightness and became a naked-eye object for several weeks (172: 309).
Five in one With the discovery of a fifth planet circling the nearby star 55 Cancri, astronomers found the most populous--and heaviest--planetary system beyond the sun's (172: 334).
Death and life An exoplanet survived after its aging parent star ballooned into a red giant that almost engulfed it (172: 163), while infrared observations depicted dusty vestiges of a planetary system dancing around a dead star (171: 100). Material shed by a dying star might give birth to planets, researchers reported (171: 62).
Planetary prelude An infrared portrait of an embryonic, sunlike star revealed an early, crucial step in the process of planet formation (172: 358).
Joe average A collection of low-mass galaxies, dating from when the universe was just 2 billion years old, appeared to be the typical building blocks of large galaxies like the Milky Way (172:373).
In transit Observations of minieclipses that occur when a distant planet passes in front of its parent star revealed new insights into the size, composition, and temperature of exoplanets (172: 24 *).
Distant dustup Some of the best evidence yet emerged for an asteroid belt beyond the solar system (171: 5 *).
Smash up Images recorded one of the biggest cosmic collisions known: four galaxies ramming into each other (172: 173).
Pondering plumes The action of Saturn's gravity generates the plumes of water vapor shooting out from cracks on the moon Enceladus (171: 350). The Cassini spacecraft will change course to take a closer look at the plumes next March (172: 110).
Dark riddle Debris from an ancient collision of galaxy clusters seemed to show cosmic dark matter behaving in a puzzling way (172: 117 *).
A spacecraft found evidence that Venus once had more water than it does today as well as proof of Venusian lighting and of a formerly unknown hot spot near the south pole (172: 339).
Heavenly chemistry Discovery of a rare, negatively charged organic molecule shed light on conditions in interstellar gas clouds, where amino acids, sugars, and other prebiologic compounds form (172: 54).
New images of the planet diminished the likelihood that liquid water has flowed on some parts of Mars, but bolstered the case in other places (172: 181 *). Evidence that Mars once had a vast ocean gained support from a proposal that the planet was tipped halfway over on its side several billion years ago (171: 373).
In the black A flotilla of X-ray-observing spacecraft homed in on the whirlpool of activity surrounding a supermassive black hole (171:8). A chance eclipse enabled astronomers for the first time to measure the width of a disk of swirling, hot matter around a supermassive black hole (171: 253).
Stellar spectaculars Astronomers reported the two brightest stellar explosions ever observed (171: 293), which could be the first examples of a rare type of supernova involving a freakishly massive star or a single star undergoing multiple outbursts (172: 269).
Passing galaxies The newly measured speeds of two familiar companion galaxies to the Milky Way suggest that they are not gravitationally bound to the Milky Way, but are relative newcomers passing by for the first time (171: 19; 172: 253).
Sun watchers Twin spacecraft began taking three-dimensional images of the sun and for the first time tracked solar storms from their birth in the lower depths of the sun's atmosphere all the way to Earth's orbit (171: 93, 133).
Tilted rings The rings of Uranus, now tilted edge-on to Earth, exhibited never-before-seen structures (172: 157).
Watery Mars Liquid may have percolated through underground rock on the Red Planet, providing a possible habitat for primitive life, suggest images of ancient cracks on Mars (171:158). An ultrasharp image of part of one Mars crater showed waterborne sediments and volcanic ash (172: 245).
Red ice The global darkening of Mars' surface in recent decades has significantly raised the Red Planet's temperature, a possible cause for the substantial, recent shrinkage of the planet's southern ice cap (171: 214). If the frozen water stored near the south pole of Mars suddenly melted, it would make a planetwide ocean 11 meters deep (171: 206). An immense volume of ice-rich material may underlie a formation that extends about one-quarter of the way around Mars' equator (172: 277).
Ringing portrait NASA's Cassini spacecraft took the most sweeping views ever recorded of Saturn's icy rings (171: 148).
Martian caverns Images taken by a Mars-orbiting spacecraft depicted what appear to be caves on the Red Planet (171: 237).
Kaput The sharpest, most sensitive camera on the aging Hubble Space Telescope stopped working (171: 68).
Dino killer unveiled The asteroid that wiped out the dinosaurs 65 million years ago may have been a wayward fragment from a violent collision in the asteroid belt (172: 148 *).
Dwarfing growth Researchers found the smallest galaxy known (171: 62). Another wispy dwarf galaxy, called Leo A, appeared to challenge models of galaxy evolution (171: 195). A small galaxy at the periphery of the giant Andromeda galaxy looked to be a galactic building block of the modern-day universe (171: 357).
Mercury's core is at least partially molten, a radar study of the planet's spin revealed (171: 277 *).
Puny Pluto Ex-planet Pluto suffered another demotion, as observations showed that it's much less massive than Eris, another distant denizen of the outer solar system's Kuiper belt (171: 413). Astronomers found the first "extended family" of related objects in the Kuiper belt (171: 164).
Heavy weight The discovery of a stellar-mass black hole almost 16 …