小惑星サンプル採取のＮＡＳＡ探査機、地球目指し帰路へ　２３年９月到着

【ワシントンＡＦＰ＝時事】地球近傍小惑星「ベンヌ」で昨年、塵（ちり）のサンプルを採取した米航空宇宙局（ＮＡＳＡ）の無人探査機「オシリス・レックス」が１０日、地球を目指し長い帰還の途に就いた。米ユタ州の砂漠に着陸するのは、２０２３年９月２４日の予定。（写真は資料写真）
　ＮＡＳＡのビデオ放送でミッションの主任研究員ダンテ・ローレッタ氏は「オシリス・レックスは帰還の途に就き、現在ベンヌから時速約９６５キロ以上で遠ざかっている」と語った。
　探査機のスラスタ（推進装置）は無事７分間にわたって作動。約２３億キロの旅路となる軌道に乗った。
　オシリス・レックスは、小惑星ベンヌで採取した塵や石のかけらなど６０グラム以上を地球へ持ち帰ろうとしている。アポロ計画の月の石以来、ＮＡＳＡが採取したサンプル量として最大となる。
　サンプルが入ったカプセルは２年半後、地球の大気圏に突入する数時間前に探査機から放出され、パラシュートによって減速されて着陸する。その後、米テキサス州ヒューストンにあるＮＡＳＡのジョンソン宇宙センターに運ばれるが、７５％はそのまま保存され、将来世代の研究に託されるという。
　ベンヌのサンプルの分析により、太陽系の形成や居住可能な惑星としての地球の進化について理解が深まることが期待される。【翻訳編集ＡＦＰＢＢＮｅｗｓ】

〔ＡＦＰ＝時事〕（2021/05/11-13:48）

The US space probe Osiris-Rex on Monday left the orbit of the asteroid Bennu, from which it collected dust samples last year, to begin its long journey back to Earth.
The probe still has a vast distance to cover before it lands in the Utah desert on September 24, 2023.
Osiris-Rex is now moving away over 600 miles an hour from Bennu, on its way home, Dante Lauretta, head of the mission, said on NASA's video broadcast of the event.
The spacecraft's thrusters were engaged without incident for seven minutes to put the probe on the correct trajectory home, a journey of 1.4 billion miles (2.3 billion kiometers).
It is carrying more than 60 grams of dust and fragments from the asteroid, the largest sample collected by NASA since the Moon rocks brought back by the Apollo missions.
To achieve this goal, the US space agency launched a high-risk operation in October 2020: the probe came into contact with the asteroid for a few seconds, and a blast of compressed nitrogen was emitted to raise the dust sample which was then captured.
The surprise for NASA was the probe's arm sank several centimeters into the surface of the asteroid, showing the scientists that the surfaces of these rubble pile asteroids are very loosely consolidated, said Lauretta.
The whole mission almost came to nought when NASA realized a few days later that the valve of the collection compartment was failing to close, letting fragments escape into space.
But the precious cargo was finally secured after being transferred to a capsule fixed in the spacecraft's center.
In two and a half years, that capsule will be released a few hours before entry into the Earth's atmosphere, and will be slowed down by a parachute system for its landing.
The samples will then be transported to NASA's Johnson Space Center in Houston, but 75 percent will be kept intact to be studied by future generations, who will have advanced technologies that have not yet been created, the agency said.
The analysis should help scientists better understand the formation of the solar system and the development of Earth as a habitable planet.