m molecular species, but 

 neither acetone nor DHA had been de- 

 tected in the two clouds before now. 



What's exciting about the discover- 

 ies is how much of the two chemicals 

 reside in the interstellar clouds. First, 

 each cloud is many times larger than our 

 solar system. Moreover, the measure- 

 ments suggest that trillions upon tril- 

 lions of tons of acetone and DHA have 

 collected in the two hot cores. Clearly, 

 conditions there must be highly favor- 

 able to the formation and maintenance 

 of the molecules. Yet such conditions 

 are hardly typical of interstellar space. 



Okay, so maybe astronauts of the 

 distant future will have no prob- 

 lem sprucing up their fingernails or 

 maintaining perfect skin tone. Acetone 

 and DHA aren't just important groom- 

 ing aids; both are basic organic mole- 

 cules, and both serve as key players in 

 many complex biochemical processes 

 on Earth. DHA, for instance, is crucial 

 to human metabolism. 



The prevalence of the two chemicals 

 in interstellar space lends support to an 

 idea about the origins of Earth's biolo- 

 gy that is becoming increasingly widely 

 accepted. Many complex molecules 

 might not have formed on Earth, but 

 were assembled elsewhere in the early 

 solar system and later deposited here as 

 raw materials for the molecules of life. 

 If conditions in the early solar nebula led 

 to some of the same molecule-making 

 that Friedel and Widicus Weaver have 

 observed in the Orion and Sagittarius 

 cloud cores, organic compounds such 

 as acetone and DHA could have been 

 incorporated into comets and planetes- 

 imals. Those bodies might then have 

 collided with Earth millions of years lat- 

 er and dropped their organic payloads 

 onto Earth's surface. If so, the biology of 

 our planet may owe its existence to an 

 interstellar cloud of gas that sowed the 

 seeds of proteins, DNA, and ultimately 

 us — not to mention the stuff that can 

 give us that "bronze-goddess glow." 



Charlbs Liu is a professor ofiistrophysiis at the 

 City University of New York and an associate 

 with the American Museum of Natural History. 



THE SKY IN FEBRUARY 



At the beginning of February Mercury 

 has just passed behind the Sun and sets 

 too soon after sunset to be seen. But 

 by the 9th the speedy planet should be 

 visible to viewers with binoculars, just 

 above the west-southwestern horizon 

 near where the Sun has disappeared 

 half an hour earlier. By the 14th Mer- 

 cury sets a full hour after the Sun and 

 is easy to see with the naked eye. 



The planet reaches greatest eastern 

 elongation (its greatest angular distance 

 from the Sun) on the 23rd, only a day 

 after it passes perihelion (its closest ap- 

 proach to the Sun). That makes for fa- 

 vorable observing in the mid-northern 

 United States, because Mercury is al- 

 most directly above the Sun, giving the 

 planet more time to shme in a dark sky 

 before setting at the end of twilight. A 

 slender crescent Moon hangs about 

 five and a half degrees below and slight- 

 ly to the left of Mercury on the 28th. 



Venus rises in a dark sky about half an 

 hour before morning twilight at the 

 beginning of February; it rises near- 

 ly half an hour earlier by month's end. 

 The planet is scooting ahead of the 

 Earth as it races around the Sun, so 

 viewers with telescopes wiU see the 

 crescent of Venus thickening in phase 

 but diminishing in overall size. Venus 

 reaches its greatest brilhancy of the 

 year — a stunning —4.6 magnitude — 

 on the 17th. 



Mars soars high in the sky this month. 

 It is near the meridian at dusk and re- 

 mains visible until about an hour to an 

 hour and a half after midnight. On the 

 evening of the 5th Mars is situated 

 about two to three degrees below the 

 Moon. The planet moves east nearly 

 fifteen degrees this month, crossing 

 from the constellations Aries, the ram, 

 into Taurus, the bull, on the 7th. 



If you watch attentively, you may be 

 able to detect changes in the color ot 

 the Red Planet. In fact, despite its 

 nickname. Mars usually looks yellow- 



By Joe Rao 



to yellow-orange. During its occa- 

 sional global dust storms, however, it 

 becomes a Hghter yellow. 



Jupiter, in the constellation Libra, the 

 scales, rises just after 1 A.M. at the start 

 of February and shortly before 1 1:30 

 P.M. near month's end. But for the best 

 views, look before morning twilight 

 begins, when the planet is well up in 

 the south. Soon after midnight on the 

 20th Jupiter rises about five to six de- 

 grees above and to the left of the wan- 

 ing gibbous Moon. 



Saturn, just past its opposition of Jan- 

 uary 27th, is low in the east at dusk 

 and visible for most of the night. The 

 planet begins the month one degree 

 south of Praesepe, the Beehive star 

 cluster in the constellation Cancer, 

 the crab. Soon after darkness on the 

 10th, the Moon appears to stand high 

 above the planet in the east. On the 

 following evening our satellite shifts 

 below and to the left of Saturn. 



The Moon waxes to first quarter on 

 the 5th at 1 :29 A.M. and to full on the 

 12th at 11:44 P.M. It wanes to last 

 quarter on the 21st at 2:17 A.M. and 

 to new on the 27th at 7:31 P.M. 



Late on the night of the 17th a wan- 

 ing gibbous Moon occults, or passes 

 in front of, Spica, a bright, bluish, 

 first-magnitude star in the constella- 

 tion Virgo, the virgin. Unfortunately 

 for most viewers in the United States, 

 the event is unobservable because it 

 takes place before the Moon and Spi- 

 ca rise. In the Northeast, however, 

 Spica will already be hidden when the 

 Moon rises, after about 10 P.M. Soon 

 after 1 1 PM., while still low and near 

 the east-southeastern horizon, Spica 

 dramatically pops out from behind the 

 dark part of the Moon as viewed with 

 binoculars or a telescope. 



Unless otiieni'isc noted, all times ine <^ireii 

 ill eastern standard time. 



February 2006 Nh VVR W nisioK^ 



59 



