Research press release


Nature Astronomy

Ice volcano activity on Ceres never froze



Michael Soriたちは今回、氷の火山ドームが次第に沈下し、最終的には周辺の地形に溶け込むという仮定に基づき、粘性緩和によるドーム形成のモデルを用いて、探査機ドーンによって撮影された画像から、ケレスにかつて存在していた22個の氷火山を同定した。著者らは、これらの地形の年代を推定し、ケレスには新しい氷火山が直近の10億年間で平均しておよそ5000万年ごとに出現していたことを明らかにした。


Ice volcanoes have erupted throughout the history of the dwarf planet Ceres, reports a study published online this week in Nature Astronomy. However, such continuous activity has not had the same extensive impact on Ceres’s surface as standard volcanism on Earth.

Instead of spewing molten rock, so-called cryovolcanoes erupt liquid or gaseous volatiles such as ammonia, water or methane. Traces of cryovolcanism have been found on several bodies in the outer Solar System. In 2015, NASA’s Dawn spacecraft orbiting Ceres discovered a dome-shaped mountain - dubbed Ahuna Mons - which was identified as a cryovolcano. However, no similar structures have been spotted on Ceres.

Based on the assumption that the icy volcanic domes gradually settle down, ultimately blending with the surrounding landscape, Michael Sori and colleagues use models of relaxing dome shapes to identify 22 former cryovolcanoes on Ceres in images taken by the Dawn mission. The authors estimate the age of these features, and find that in the last billion years, new cryovolcanoes have appeared on Ceres around every 50 million years on average.

The authors also estimate that the total amount of icy material that has been erupted onto the surface of Ceres is one hundred to one hundred-thousand times less than the volumes of molten rock erupted on the Earth, Moon, Venus or Mars.

doi: 10.1038/s41550-018-0574-1

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