Research press release


Nature Geoscience

A dry ice solution to Mars’s gullies



Cedric PilorgetとFrancois Forgetは、斜面の表面を覆ったCO2の氷の層が解凍するにつれて、捕獲されたCO2の気体が氷の層の下で蓄積され、結果的にその下の土壌を不安定にさせて、気体と岩屑の流れの引き金となるという説を提示している。Pilorgetたちは、数値モデルを用いてこの過程をシミュレーションし、ドライアイスが駆動する過程は、火星における分布を含む小峡谷で観察される多くの特徴を説明できることを示した。

同時掲載のNews & Views記事で、Colin Dundasは、「他の世界を論じるときには、そこではなじみのないプロセスが可能であり、それは未知の環境ではなおさらであるということを注意して覚えておかねばならない」と述べている。

Gullies on Mars may be sculpted by dry ice processes, rather than flowing liquid water, according to a study published online this week in Nature Geoscience. The study suggests that, although the Martian gullies may look like water-sculpted gullies on Earth, the underlying processes may be very different.

Gullies-small valleys cut into slopes-found at the Martian mid-latitudes appear similar in shape to gullies formed by flowing streams on Earth, suggesting a common origin. However, the modern surface environment of Mars is too cold at the gully locations to support large volumes of liquid water. The gullies are less than a few million years old-with some actively forming today-and seasonally active on slopes during times that coincide with defrosting carbon dioxide (CO2) ice on the Martian surface, indicating that dry ice may be involved in their formation.

Cedric Pilorget and Francois Forget propose that, as a layer of CO2 ice that coats a sloped surface defrosts, trapped CO2 gas builds up beneath the ice layer, eventually destabilizing the underlying soils and triggering a flow of gas and debris. The authors use a numerical model to simulate this process and show that the dry-ice-driven process can explain many of the gullies’ observed features, including their distribution across the Red Planet.

In an accompanying News & Views article, Colin Dundas notes that: “When dealing with other worlds, we must take care to remember that unfamiliar processes are possible and even likely in alien environments.”

doi: 10.1038/ngeo2619


メールマガジンリストの「Nature 関連誌今週のハイライト」にチェックをいれていただきますと、毎週各ジャーナルからの最新の「注目のハイライト」をまとめて皆様にお届けいたします。