Research press release


Nature Geoscience

Mercury the shrinking planet


Paul Byrne等は、メッセンジャー探査機により取得された画像を用いて、水星表面の尾根や断層の位置を特定した。これらの地質学的構造は、惑星の地殻が、最初は高温だった惑星が冷えて縮まる際に起きる圧縮による座屈や破砕によって形成されたと考えられている。研究者たちは、尾根や断層により地殻が変位した総量を足し合わせて、水星表面積の減少は、惑星の半径が最大7キロメートル失われたことに匹敵することを発見した。


関連するNews & ViewsでWilliam McKinnonは「収縮している惑星で何が実際に起きうるかについての例を水星は提供している」と書いている。

The planet Mercury has shrunk in size by as much as seven kilometres across its radius over the past four billion years, according to a study published online in Nature Geoscience. The findings suggest that Mercury has contracted much more than previously estimated.

Paul Byrne and colleagues mapped ridges and faults across the surface of Mercury using images acquired by the MESSENGER spacecraft. These geologic structures are thought to have formed through the buckling and fracturing of the planet’s crust, due to compression as the initially hot planet cooled and contracted. The researchers added up the total amount of crust displaced by the ridges and faults, and found that the total reduction of Mercury’s surface is equivalent to a loss of up to seven kilometres of the planet’s radius.

Intriguingly, the observed deformation of Mercury’s surface is consistent with a nineteenth-century theory for a shrinking Earth. This theory has long been obsolete for our planet, as Earth’s surface is broken into plates, but Mercury is enclosed by a single plate and cannot lose its heat through plate tectonics processes.

In an accompanying News and Views article, William McKinnon writes that, “Mercury provides an example of what may really happen to a planet that is shrinking.”

doi: 10.1038/ngeo2097


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