太陽系首顆未受損的小行星（圖）

06-11

太陽系首顆未受損的小行星（圖）

First Solar System Leftover

Planetary scientists weren"t sure what sort of asteroid they were looking at when the European Space Agency"s Rosetta spacecraft flew close by Lutetia on 10 July 2010. But online today in Science, they report that the 121-kilometer-long asteroid is most likely the first object among the 10,000-plus known asteroids to be recognized as an intact planetesimal of the sort that glommed together to form the planets 4.6 billion years ago. The tip-off was its high density, as gauged by the way Lutetia"s gravity deflected the passing spacecraft. The rocky body—the largest yet to get a close flyby—seems to have been just large enough to avoid being reduced to a flying pile of rubble by eons of collisions with other asteroids. The quick look has left researchers still scratching their heads over the planetesimal"s mineralogical makeup, but Rosetta has moved on to bigger things: a 2014 landing on comet Churyumov-Gerasimenko.

2010年7月10日，當歐洲航天局的「羅塞塔」號太空船飛近小行星「魯特西亞」的時候，行星科學家們不能夠確定他們看到是怎樣一種小行星。今天，研究人員在《科學》雜誌在線版上報道說，在46億年以前凝結在一起形成的10000多顆已知小行星中，這顆長為121公里的小行星很可能是首顆被認定為完好無損的小行星體。揭示這個情況的是這顆小行星的密度，密度是通過測量魯特西亞的引力對經過的飛船所造成偏斜度來獲得的。這顆岩石星體是飛船將要靠近的最大的小行星，該小行星的塊頭好像剛好夠大，不至於在多個時代以來由於跟其他小行星碰撞而淪落為一堆飛行的碎石塊。這匆匆地一瞥使得研究人員對於該小行星的礦物學構成仍然感到困惑。但是，「羅塞塔」號太空船將要繼續執行一個更大的任務：2014年在丘尤穆夫-傑拉西門科彗星上著陸。