【英语时差8,16】类地球星体--火星（在线收听）

Earth-Like Mars For decades, scientists have been fascinated by the prospects that Earth’s next‑door neighbor once harbored life. And although no hard evidence has yet been found, scientists are still hopeful that signs of life–past and possibly present–will still turn up. Because Mars missions, like the Phoenix Mars Lander, have shown that in many ways Mars isn’t so very different from our planet. Yes, Mars appears to be dusty and dry, at least on the surface. But at its poles, the so‑called Red Planet is intriguingly Earth‑like. For example, the Phoenix Lander found traces of the mineral calcite, suggesting that Mars still has an active water cycle. Just like on Earth, Mars once had large salty lakes and rushing rivers that cut canyons and deposited deltas. And where there was once water, there may very well have been life. But even though Martian water is mostly long gone from the surface, Mars still resembles Earth in many ways. Similar to Antarctica, Mars’ north polar region contains ice just below the pebbly surface. And at least some of that ice is mixed with soil containing nutrients that could support life. And every few million years, the Martian ice caps melt. This could mean winter snowstorms and even summer wetlands similar to tundra regions on Earth. So does this mean that Mars once teemed with living things? Not necessarily. But bacteria and other microscopic organisms can live even in the most extremely cold and dry environments on Earth. So life may not only have thrived on Mars in the ancient past. It could still be there today, hiding in the icy subsurface and waiting to bloom when the climate is right.

转自可可英语