This lava field just north of the Mýrdalsjökull ice cap serves as one of many monitoring sites to track ground deformation that could serve as a signal of an impending eruption of Katla.

这片位于米达尔斯冰盖北部的熔岩原是用来追踪地面形变的监测点之一，这里地面的形变可以被视为卡特拉火山喷发的前兆。

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As often seen through an astronomical telescope eyepiece, the planet's orientation is inverted, with Mars' north polar cap at the bottom.

由于往往是通过天文望远镜的目镜拍摄，火星的方向是颠倒的，行星的北极冠在下面。

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In 2007, a Russian expedition descended in a pair of vessels more than two miles under the ice cap and deposited a Russian flag on the seabed at the North Pole.

2007年，一支俄罗斯探险队在北极用两艘潜水器潜到了两英里之下的冰层，并在海底放置了俄罗斯国旗。

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They were photographed in September 1998 in Chasma Boreale, a giant trough at Mars' north polar cap.

CNN: Scientists debate implications of Mars pictures

But the volume of the Martian north polar cap is less than half that of the Greenland ice cap, and about four percent of the Antarctic ice sheet.

BBC: By BBC News Online Science Editor Dr David Whitehouse

The estimated volume of the north ice cap is about 10 times less than the minimum volume of an ancient ocean that some scientists believe once existed on Mars.

BBC: By BBC News Online Science Editor Dr David Whitehouse