NASA scientists took time on Wednesday (Nov. 28) to soothe 2012 doomsday fears, warning against the dark side of Mayan apocalypse rumors — frightened children and suicidal teens who truly fear the world may come to an end Dec. 21.
These fears are based on misinterpretations of the Mayan calendar. On the 21st, the date of the winter solstice, a calendar cycle called the 13th b'ak'tun comes to an end. Although Maya scholars agree that the ancient Maya would not have seen this day as apocalyptic, rumors have spread that a cosmic event may end life on Earth on that day.
wo hours before closest approach to Neptune in 1989, the Voyager 2 robot spacecraft snapped thispicture. Clearly visible for the first time were long light-colored cirrus-type clouds floating high in Neptune's atmosphere. Shadows of these clouds can even be seen on lower cloud decks. Most of Neptune's atmosphere is made of hydrogen and helium, which is invisible.Neptune's blue color therefore comes from smaller amounts of atmospheric methane, which preferentially absorbs red light. Neptune has the fastest winds in the Solar System, with gusts reaching 2000 kilometers per hour. Speculation holds that diamonds may be created in the dense hot conditions that exist under the cloud tops of Uranus and Neptune. Twenty-six years later,NASA's New Horizons is poised to be the first spacecraft to zoom past Pluto this July.
What causes the structure in Comet Lovejoy's tail? Comet C/2014 Q2 (Lovejoy), which is currently at naked-eye brightness and near its brightest, has been showing an exquisitely detailed ion tail. As the name implies, the ion tail is made of ionized gas -- gas energized by ultraviolet light from the Sun and pushed outward by the solar wind. The solar wind is quite structured and sculpted by the Sun's complex and ever changing magnetic field. The effect of the variable solar wind combined with different gas jets venting from the comet's nucleus accounts for the tail's complex structure. Following the wind, structure in Comet Lovejoy's tail can be seen to move outward from the Sun even alter its wavy appearance over time. The blue color of the ion tail is dominated by recombining carbon monoxide molecules, while the green color of the coma surrounding the head of the comet is created mostly by a slight amount of recombiningdiatomic carbon molecules.
