托福阅读资料之什么是南极地衣

　　Although ninety-eight percent of Antarctica is covered by thick ice, there are bare patches where the rocky surface shows through. These so-called “dry valleys” are some of the most inhospitable places on Earth. Air temperature is well below freezing, and it’s dry as a desert because arid, hurricane-force winds suck the snow and other moisture away.

　　If you were a microorganism in one of Antarctica’s dry valleys, where would you hide to escape the biting, arid wind?

　　For a cryptoendolith, the answer is inside a rock. These Antarctic cryptoendoliths are a type of lichen whose very name translates as “hiding inside rocks.” Even in this cold, dry land, these lichen need a certain amount of warmth and moisture to survive. How does living inside a rock help them keep warm and wet?

　　These lichen live a fraction of an inch inside pieces of porous sandstone. They prefer north-facing stones, which absorb sunlight and heat up during the day.

　　Even if the air stays bitterly cold, these sunbaked rocks can warm enough to melt whatever tiny patches of snow have escaped the thirsty wind. The water is quickly absorbed by the porous rock, and it can stay inside for weeks–freezing and re-melting as the rock warms and chills.

　　Of course the lichen freeze and thaw too, as much as several times an hour during a particularly rough day. But they get just enough heat, and just enough moisture, to stay alive. Which is what survival is all about anyway.

　　译文

　　提到南极洲，眼前浮现的是一片荒凉的冰域，毫无生命气息，凛冽刺骨的风拍打着这块土地。

　　尽管南极洲98%的土地都被厚厚的冰覆盖着，但岩石表面仍然有一些次生裸地。这些所谓的“干旱河谷”是地球上十分荒凉的地方。那里的气温远远低于结冰点，同时由于强大的飓风吸收了雪和其他的水分，这又是一个干旱的荒漠。

　　假如说您是南极洲干谷里的一种微生物，是否能想到在哪里能躲过这干燥刺骨的风?