When positronium collides, quadruple Pluto system and alternatives to carbon-based life

Welcome! "Alien Life" tracks the latest discoveries and thoughts in the various elements of the famous Drake Equation. Here's today's news:
g Stars - What happens when two atoms, each made up of an electron and its antimatter counterpart, called the positron, collide with each other? UC Riverside physicists are able to see for the first time in the laboratory that these atoms, which are called positronium atoms and are unstable by nature, become even more unstable after the collision. The positronium atoms are seen to destroy one another, turning into gamma rays, a powerful type of electromagnetic radiation. See article.
g Abodes - A team of astronomers at Southwest Research Institute and other institutions has discovered that Pluto has two previously unseen moons. Ground-based observers discovered Pluto's only previously known moon, Charon, in 1978. The planet itself was discovered in 1930 and orbits about 4 billion miles from the Sun in the heart of the Kuiper Belt. By virtue of its location in the Kuiper Belt, planet Pluto is also considered a Kuiper Belt object. The newfound satellites make Pluto a "quadruple" system. See article.
g Life - All life on this planet is carbon-based. Carbon atoms readily form a strong bond between themselves and a range of other atoms, most importantly hydrogen, oxygen and nitrogen, but it is the strength of the carbon-carbon bond that is most significant. This allows carbon atoms to be linked together in chains and rings, building up an unimaginably vast range of compounds. Oxygen and nitrogen, in contrast, too readily form the diatomic molecules (O2 and N2) to form chains. Fluorine, chlorine and the other halogens, and hydrogen are monovalent, so cannot form chains. The noble gases are inert. So what alternatives are there? See article.
g Intelligence - While changing sex from female to male, the highly social bluebanded goby becomes more aggressive. At the same time, the conversion of testosterone to estrogen slows in the brain, but is unaffected in the changing gonads, according to a Center for Behavioral Neuroscience study in the current on-line edition of Proceedings of the Royal Society B. The finding, which suggests the initial stages of sex change in fish are regulated in the brain, could help better explain the biological basis of human sexual identity. See article.
g Message - Book alert: Scour your used bookstore shelves for "Life Beyond Earth," by Timothy Ferris. Rock-solid science writer Ferris has covered this ground before. In the two-hour PBS documentary that he wrote and narrated - which shares the title, text, and many of the images of this generously illustrated book - Ferris tackles two age-old questions about the potentially universal nature of life: Are we alone, and, if not, is anybody listening? See reviews.
g Cosmicus - While recognizing that many of the driving forces behind human space flight are social and political, rather than narrowly scientific, it seems clear that science has been, and will continue to be, a major beneficiary of having people in space. What, after all, is the alternative? We can either stay at home, sending a few robot spacecraft to our neighboring planets, and continuing to gaze at the more distant universe across light years of empty space, or we can get ourselves out among the planets and, eventually, the stars. In which alternative future would we learn the most about this universe and our place within it? See article.
g Learning - Here’s a neat essay: "Our blunder: Clinging to unbelievable beliefs." See essay.
g Imagining - Here’s an interesting critical examination of science fiction aliens that’s worth reading: John Huntington’s "Discriminating Among Friends: The Social Dynamics of the Friendly Aliens," in "Aliens: The Anthropology of Science Fiction," George E. Slusser, ed., 1987). It includes a discussion of Weinbaum's classic short story "Martian Odyssey."
g Aftermath - Quote of the Day: "We would be foolish and negligent if we did not try to anticipate such reactions (of first contact) and make careful preparations." — Albert Harrison

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