慧星演變說，pristine relics 　　The long-held perspective that comets are pristine remnants（殘留部分） from the formation of the solar system has evolved（演變發(fā)展） from the prevailing views of 30 years ago, finds planetary scientist Dr. S. Alan Stern in a paper published in the journal Nature. 　　行星學家Stern博士發(fā)現(xiàn)（在Nature上的一篇paper中）：長久以來的一種觀點“彗星是太陽系形成時的原始殘留物”是30年前一種流行觀點的演化。 　　"It's fair to say that a sea change has taken place," says Stern, director of the Space Studies Department in the SwRI Space Science and Engineering Division. "We used to consider comets as wholly unchanged relics that had been stored ever since the era of solar system formation in a distant, cold, timeless deep freeze called the Oort cloud. We now appreciate that a variety of processes slowly modify comets during their storage there," he says. "As a result, it's become clear that the Oort cloud and its cousin the Kuiper Belt are not such perfect deep freezes." 　　我們過去認為彗星是從太陽系建立時起就存儲在一個distant, cold, timeless deep freeze的叫做Oort cloud中不變的殘余物。我們現(xiàn)在認為存儲時許多緩慢的過程改變了彗星，所以很明顯Oort cloud和Kuiper Belt不是完美的deep freezes。 　　The first evolutionary process to be recognized as affecting comets during their long storage was radiation damage, followed by the discovery that sandblasting from dust grains in the interstellar medium plays an important role. Next, researchers theorized that comets in the Oort cloud are heated to scientifically significant temperatures by passing stars and supernovae, says Stern. More recently, researchers are finding that comets in the Kuiper Belt are heavily damaged by collisions. 　　第一個進化過程：放射損壞，在一個發(fā)現(xiàn)。。。之后。然后，研究者認為Oort cloud中的彗星在經過stars and supernovae時被加熱。最近，研究者發(fā)現(xiàn)Kuiper Belt里的彗星損毀嚴重。 　　"It also now seems inevitable that most comets from the Kuiper Belt, though constructed of ancient material, cannot themselves be ancient -- instead they must be 'recently' created chips off larger Kuiper Belt Objects, formed as a result of violent impacts," says Stern. "This is truly a paradigm shift. Many of the short-period comets we see aren't even ancient!" 　　我們看見的彗星其實已經被損壞了，不是ancient。 　　The classical view that comets do not evolve while they are stored far from the sun in the Oort cloud and Kuiper Belt began to change as far back as the 1970s, but the pace of discoveries about the way comets evolve picked up considerably in the 1980s and 1990s. 　　不變的觀點可以追溯到1970s，發(fā)現(xiàn)彗星演變的步伐加速發(fā)生在1980 s and 1990s 　　As a result of these findings, astronomers now better appreciate that comets, though still the most pristine bodies known, have been modified in several important ways since their birth, says Stern. 　　作為上述發(fā)現(xiàn)的結果，天文學家現(xiàn)在認為彗星雖然還是已知的最原始的東西，但的確從誕生開始在某些重要的方面發(fā)生了改變。 　　The realization that comets evolve during their long storage in the Oort cloud and Kuiper Belt provides insight and context to more confidently evaluate the results of astronomical and space mission observations of comets. So, too, it suggests that cometary sample return missions now on the drawing board for NASA should employ relatively deep subsurface sampling if truly pristine, ancient material is to be collected. 　　意識到彗星演變 給更可信的評估彗星觀測結果 提供了遠見和背景。它也表明如果收集到更原始的彗星樣本，應該用相對深的表面的樣本。