- NASA 的"好奇号"探测车在火星盖尔陨石坑挖出的岩石里，发现了确凿的有机分子证据——这是地球生命构成的基本要素，但科学家立刻强调"这不等于火星有生命"。
- 更早在 2014 年，好奇号还发现火星大气里有甲烷，而甲烷只能存在几百年，这意味着火星地下一定有什么东西在持续"补充"甲烷，甲烷浓度甚至跟着季节起伏，像是"星球在呼吸"。
- 科学家猜测甲烷来自地下的笼形水合物，冬天封存、夏天融化释放，但"甲烷到底从哪来"仍是一个完全没解开的谜。
- 欧洲太空局的 ExoMars 和 NASA 的下一台火星车都计划在 2020 年前后带着更精密的仪器登陆，专门去追问这两个发现背后的答案。
重点内容
原文 / 段落
A new study published in the journal *Science* shows definitive evidence of organic matter on the surface of Mars. The data was collected by NASA's nuclear-powered rover Curiosity. It confirms earlier findings that the Red Planet once contained carbon-based compounds. These compounds – also called organic molecules – are essential ingredients for life as scientists understand it.
The organic molecules were found in Mars's Gale Crater, a large area that may have been a watery lake over three billion years ago. The rover encountered traces of the molecule in rocks extracted from the area. The rocks also contain sulfur, which scientists speculate helped preserve the organics even when the rocks were exposed to the harsh radiation on the surface of the planet.
Scientists are quick to state that the presence of these organic molecules is not sufficient evidence for ancient life on Mars, as the molecules could have been formed by non-living processes. But it's still one of the most astonishing discoveries, which could lead to future revelations. Especially when one considers the other startling find that Curiosity uncovered around five years ago.
The rover analyses the air around it periodically, and in 2014 it found the air contained another of the most basic organic molecules and a key ingredient of natural gas: methane. One of the characteristics of methane is that it only survives a few hundred years. This means that something, somewhere on Mars, is replenishing the supply. According to NASA, Mars emits thousands of tons of methane at a time. The level of methane rises and falls at seasonal intervals in the year, almost as if the planet is breathing it.
NASA suspects the methane comes from deep under the surface of the planet. The variations in temperature on the surface of Mars cause the molecule to flow upwards at higher or lower levels. For example, in the Martian winter the gas could get trapped in underground icy crystals. These crystals, called clathrates, melt in the summer and release the gas. However, the source of the methane is still a complete mystery.
The world of astrobiology considers both of these studies as historical milestones. According to this information, Mars is not a dead planet. On the contrary, it is quite active and may be changing and becoming more habitable.
Of course, this means further research is necessary. Scientists say they need to send new equipment to Mars, equipment that can measure the air and soil with more precision. There are already missions underway. The European Space Agency's ExoMars ship lands in 2020 and will be able to drill into the ground on Mars to analyse what it finds. Additionally, NASA is sending another Mars Rover in the same year to collect samples of Martian soil and return them to Earth.
The possibility of life on Mars has fascinated humans for generations. It has been the subject of endless science-fiction novels and films. Are we alone in the universe or have there been other life forms within our Solar System? If the current missions to the Red Planet continue, it looks as if we may discover the answer very soon.
生词表
| 英文 | 中文 | 备注 |
|---|---|---|
| definitive | 确凿的、决定性的 | definitive evidence：确凿证据 |
| organic matter/molecule | 有机物质/分子 | 生命构成的基本要素 |
| speculate | 推测 | scientists speculate：科学家推测 |
| sufficient | 足够的 | not sufficient evidence for life：证据不足以证明有生命 |
| astonishing | 令人惊讶的 | one of the most astonishing discoveries |
| replenish | 补充、重新填满 | replenishing the supply：补充甲烷供应 |
| clathrate | 笼形水合物 | 一种能困住气体分子的冰晶结构 |
| habitable | 适合居住的 | becoming more habitable |
| astrobiology | 天体生物学 | 研究地外生命可能性的学科 |
| drill into | 钻入 | drill into the ground：钻入地表 |
| milestone | 里程碑 | historical milestones |
理解要点
- 区分"已经证实的事实"（有机分子确实存在、甲烷浓度确实随季节变化）和"科学家的推测"（甲烷来自地下笼形水合物），这两层信息全文交替出现，读的时候要留意 speculate/suspect 这类动词，它们标记的是推测而不是定论。
- 第三段"Scientists are quick to state"是全文态度的关键句——作者刻意提醒读者不要过度解读发现，这种"先给证据、马上降温"的写法在科普报道里很常见。
- 甲烷"像呼吸一样"的比喻是理解那段最直观的钥匙，抓住这个比喻就能理解"季节性起伏、需要持续补充"这两个关键事实。
- 最后提到的两个探测计划（ExoMars、NASA 新火星车）是全文论证的落点——目前的发现只是引出问题，真正的答案要等这些未来任务。
Sources
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