タイタンでは,広範囲に広がる朝の雨が降っています

Máté Adámkovics¹, Michael H Wong, Conor Laver

¹Department of Astronomy, University of California, Berkeley, CA 94611, USA. mate@berkeley.edu

Science (New York, N.Y.)

|October 13, 2007

まとめ

科学者たちは初めてタイタンの大気中にメタン雨を直接観測した. この発見は,月の最も明るい大陸であるXanaduで発生する降雨を明らかにしています.

科学分野:

惑星科学は惑星科学である.
大気科学大気科学
天体生物学アストロバイオロジー

背景:

タイタンの大気にはメタン雲があり,降雨が予想されていることが知られている.
降水とその地理的位置の直接的な観測は,未だに難解である.

研究の目的:

タイタンの大気中の降雨を直接観察し,特徴づけること.
タイタンのメタン雨に関連する地理的地域と条件を特定する.

主な方法:

極大望遠鏡 (VLT) とW・M・ケック天文台から得られた近赤外線スペクトルの分析.
濃縮メタンと雨を特定するために大気中の絶滅プロフィールの回収.

主要な成果:

タイタンの朝側にあるトロポスフィアの大気不透明性の向上を観測した.
高度30km近くのメタン雲と,その下にあるメタン雨の一貫した証拠.
湿度は赤道地域,特にXanadu大陸の上部で検出されました.
雲と降雨は光学的に薄い2.0マイクロメートルで,滴の大きさは0.1ミリメートル以上です.

結論:

この研究は,タイタンのメタン降水の最初の直接的な証拠を提供します.
この発見は,昼間の気温の梯度,メタンの相対湿度,風,地形がメタンの凝縮と雨を助長することを示唆しています.
観測された"見えない"雲とXanaduの上の雨は,タイタンの水循環に関する新しい洞察を提供します.

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