AT first glance, the vast area of barren red rock that makes up Beacon Valley could be the Nevada desert. It is certainly a desert 鈥� it may not have rained here for fifteen million years. But it鈥檚 a lot farther from civilisation than Nevada. Beacon Valley is hidden away in the interior of Antarctica, 100 kilometres southwest of McMurdo Sound.
So why no ice and snow? The mountains that surround Beacon Valley keep the ice cap that covers the rest of Antarctica at bay, and the surrounding regions are so cold that almost all the moisture is frozen out of the air long before the winds reach Beacon Valley. The result is a strange environment that scarcely belongs on Earth.
And that鈥檚 its big attraction. 杏吧原创s have been coming here because this is the nearest thing to the Martian landscape you can find on our planet. One recent visitor is James Head, a planetary scientist at Brown University in Rhode Island. He worked on the Apollo programme in the 1960s and last year helicoptered into Beacon Valley with geologist David Marchant of Boston University. For six weeks they worked and lived here with only a tent to call home. And they returned with intriguing evidence that glaciers were once at work on Mars.
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Landforms they found in Beacon Valley bear some striking similarities to unusual features on Mars. More than 20 years ago, a Viking orbiter captured images of a bizarre series of concentric grooves on the west flank of the Martian volcano Arsia Mons. There are over a hundred grooves, each one several hundred kilometres long. Together they look like part of a giant gramophone record.
The ridges that Head and Marchant found in Beacon Valley hint at an explanation. They are formed by a kind of glacier that exists only where the atmosphere is very cold and dry. When such glaciers retreat, their ice doesn鈥檛 melt, but instead sublimes straight into water vapour. Millions of years ago, a giant glacier passed through Beacon Valley, and as it retreated it just turned into thin air, dropping the debris it had accumulated in neat lines at its margin. With each retreating step it laid down another line of rubble. In a normal 鈥渨et鈥� glacier, streams of meltwater would have washed them all away.
Near to the strange grooves on Mars are other odd patterns of piled-up rocks. Similar features in Beacon Valley can be traced back to thick layers of rock that accumulated on top of the oldest parts of the glacier. Blanketed beneath this debris is ice that is now over 8 million years old.
That suggests that there could be hidden ice on Arsia Mons. And if there is ice, is there life too? Beacon Valley has answered some questions about Mars. But it is throwing up even more exciting ones.