On March 16, it was revealed on Nature Geoscience that Mercury, the...

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Apr 9, 2014 08:38
On March 16, it was revealed on Nature Geoscience that Mercury, the most inside planet in the solar system, has shrunk for the past four billion years more than it was expected.

Mercury's diameter is approximately 4,880 kilometers.
However, according to Paul Burn at the Carnegie Institution for Science, its diameter has contracted by approximately 14 kilometers because its inward has been cooled.
This is twice as much as it was estimated.
Unlike the Earth consisting of multiple plates, Mercury consists of a single hard crust, so there are some valleys due to contraction.
The research team has looked into more than 5,900 geography data and has calculated how long Mercury has shrunk.
In 1970s, a probe vehicle took photos of 45% of the Mercury surface and it was estimated that the Mercury contraction was from 2 to 4 kilometers diameters.
― A Japanese article ―
太陽系の惑星のうち最も内側にある水星の直径がこの40億年で推計よりも小さくなったとする研究報告が、英科学誌ネイチャー・ジオサイエンスに16日発表された。

水星の直径は約4880キロだが、米カーネギー研究所のポール・バーン氏らによる研究によると、惑星内部が冷却されたことにより、これまでに約14キロ縮小。これは従来の推計値の2倍以上だという。
地殻が複数のプレートでできる地球とは違い、水星の地殻は単一の固い層から成り、収縮でできた谷が見られる。研究チームは、5900以上の地形データを調べ、水星がどれだけ縮小したか計算した。
1970年代に探査機が地表約45%を撮影した画像データからは、水星の縮小幅は直径2─4キロという推計が出ていた。
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