The egg definitely came before the chicken in this case — the skeleton is from a modern adult kiwi, the egg from its much bigger, long-extinct cousin, Aepyornis maximus. Kyle Davis and Paul Scofield/Canterbury Museum hide caption

itoggle caption Kyle Davis and Paul Scofield/Canterbury Museum

Being able to insert the two man-made letters into DNA, alongside the usual four-letter alphabet, could teach old cells new tricks and lead to better drugs, researchers say. courtesy of Synthorx hide caption

itoggle caption courtesy of Synthorx

Botulism bacteria, or Clostridium botulinum, grow in poorly preserved canned foods, especially meat and fish. The microbe's toxin could be lethal as a bioweapon. Dr. Phil Luton/Science Photo Library/Corbis hide caption

itoggle caption Dr. Phil Luton/Science Photo Library/Corbis

An artist's rendering of Kepler-186f, the first validated Earth-size planet to orbit in the habitable zone of a distant star. T. Pyle/NASA/SETI Institute/JPL-Caltech hide caption

itoggle caption T. Pyle/NASA/SETI Institute/JPL-Caltech

The world must cut its greenhouse gas emissions to meet its goals, climate experts said Sunday. Members of the Intergovernmental Panel on Climate Change (left to right) Youba Sakona, Ramon Pichs Madruga, Ottmar Edenhofer and Rajendra Pachauri hold copies of their new report in Berlin. John MacDougall/AFP/Getty Images hide caption

itoggle caption John MacDougall/AFP/Getty Images

Street vendors sell chickens at a market in Phnom Penh, Cambodia, in early 2013. Last year Cambodia reported more cases of H5N1 bird flu than any other country. Mak Remissa/EPA /LANDOV hide caption

itoggle caption Mak Remissa/EPA /LANDOV

Where's the moon rock? Curators say national treasures are often overlooked in the museum's current display, which hasn't changed much since 1976. National Air and Space Museum, Smithsonian Institution hide caption

itoggle caption National Air and Space Museum, Smithsonian Institution

Japan Aerospace Exploration Agency astronaut Aki Hoshide makes a space walk outside the International Space Station in 2012. NASA/Getty Images hide caption

itoggle caption NASA/Getty Images

This diagram for the outer solar system shows the orbits of Sedna (in orange) and 2012 VP113 (in red). The sun and terrestrial planets are at the center, surrounded by the orbits (in purple) of the four giant planets — Jupiter, Saturn, Uranus and Neptune. The Kuiper belt, which includes Pluto, is shown by the dotted light blue region. Scott S. Sheppard/Carnegie Institution for Science hide caption

itoggle caption Scott S. Sheppard/Carnegie Institution for Science

Early days: NASA's International Sun-Earth Explorer C (also known as ISEE-3 and ICE) was undergoing testing and evaluation inside the Goddard Space Flight Center's dynamic test chamber when this photo was snapped in 1976. NASA hide caption

itoggle caption NASA

The Hadean zircons --€ the” oldest bits of Earth yet found --€” were discovered near here, on a sheep ranch in Jack Hills, Western Australia. Courtesy of University of Wisconsin hide caption

itoggle caption Courtesy of University of Wisconsin

Climbing robots, modeled after termites, can be programmed to work together to build tailor-made structures. [Image courtesy of Eliza Grinnell, Harvard School of Engineering and Applied Sciences hide caption

itoggle caption [Image courtesy of Eliza Grinnell, Harvard School of Engineering and Applied Sciences