VOA慢速英语2019 美国宇航局收集到的数据表明土卫六类似地球可能存在生命（在线收听）

For the first time, scientists have mapped the whole surface of Titan, the largest moon around Saturn. The map confirms existing data showing that Titan has many Earth-like qualities that might be able to support life.

科学家首次绘制了土星最大卫星土卫六的整个表面地图。该地图证实了现有数据，表明土卫六具有许多类似地球可以维持生命的特性。

The data was collected by Cassini, a spacecraft operated by the U.S. space agency NASA. The spacecraft studied Saturn and its moons from 2004 to 2017. Astronomers used images and radar measurements from Cassini to create the geological map of Titan.

这些数据是由美国宇航局操控的卡西尼号太空飞船收集到的。该飞船从2004年到2017年研究了土星及其卫星。天文学家使用卡西尼号拍摄的影像和雷达测量结果绘制了土卫六的地质图。

The map shows Titan as a mixture of flat plains, hills and mountains, windblown sand areas, valleys and lakes. The mapping operation is described in a report published in Nature Astronomy.

该地图显示土卫六是平原、丘陵、山脉、风沙区、山谷和湖泊的混合体。《自然天文学》发表的报告描述了这一制图过程。

Rosaly Lopes led the project. She is a planetary scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. Lopes told the publication that the many similarities between Earth and Titan make the Saturn moon a great choice for continued exploration.

罗莎莉·洛佩斯领导了这个项目。她是美国加州帕萨迪纳市美国宇航局喷气推进实验室的一名行星科学家。洛佩斯告诉该杂志，地球和土卫六之间的许多相似之处使得这颗土星的卫星成为继续探索的绝佳选择。

"Titan has an atmosphere like Earth. It has wind, it has rain, it has mountains," Lopes said. "It's a really very interesting world, and one of the best places in the solar system to look for life."

洛佩斯表示：“土卫六有跟地球一样的大气层。它有风，有雨，有山。这是一个非常有趣的世界，是太阳系中寻找生命的最佳场所之一。”

Titan is the only planet in our solar system besides Earth to have known bodies of liquid on its surface. But Titan's seas and lakes are filled with liquid methane rather than water. Methane, a gas, behaves as a liquid on Titan because the planet is extremely cold.

土卫六是太阳系中除地球以外唯一表面具有已知液体的行星。但是土卫六的海洋和湖泊充满的是液态甲烷，而不是水。甲烷是一种气体，在土卫六表现为一种液体，因为这颗星球非常冷。

At cold temperatures, methane goes through similar changes as rain on Earth. It falls to the surface across the planet to form rivers and lakes and can then evaporate to form clouds again.

在低温下，甲烷与地球上的雨水经历了类似的变化。它落在地表形成河流和湖泊，然后又蒸发成云。

The map found that nearly two-thirds of Titan's surface is made up of flat plains, Nature reported. About 17 percent is covered in sandy hills shaped by the wind, mostly around the equator.

据《自然》杂志报道，该地图发现土卫表面近2/3是平坦的平原。大约17%被风形成的沙丘覆盖，大部分在赤道附近。

Unlike Earth, Titan's sand is made up of carbon, hydrogen, nitrogen and oxygen. Around 14 percent of the surface is considered hilly or mountainous.

与地球不同，土卫六的沙子由碳、氢、氮和氧组成。大约14%的地表被认为是丘陵或山区。

Seas and lakes filled with liquid methane cover an estimated 1.5 percent of Titan. The liquid exists mainly closer to the planet's poles, while the equatorial areas remain drier.

充满液态甲烷的海洋和湖泊覆盖了土卫六1.5%的面积。这些液体主要存在于更靠近该星球两极的地方，而赤道地区则更干燥。

Ralph Lorenz is a planetary scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. He told the publication one of Cassini's most interesting discoveries "is that Titan is so diverse." Lorenz added: "It's almost like a completely different world, and this systematic mapping marshals that diversity."

拉尔夫·洛伦兹是位于马里兰州劳雷尔市的约翰·霍普金斯大学应用物理实验室的一名行星科学家。他对该杂志表示，卡西尼号最有趣的发现是“土卫六是如此多样。”洛伦兹还说：“这几乎就是一个完全不同的世界，这种系统化制图收集了这种多样性。”

Rosaly Lopes says organic materials – those containing carbon - in Titan's atmosphere are important for the growth of living organisms. "Organics are very important for the possibility of life on Titan, which many of us think likely would have evolved in the liquid water ocean under Titan's icy crust," she said.

洛佩斯表示，土卫六大气中这些含碳的有机物质对生物的生长至关重要。她说：“有机物对土卫六存在生命的可能性来说非常重要，我们很多人认为有机物可能会在土卫六冰冷地壳下的液态海洋中进化。”

Scientists believe the mixing of organic material and liquid could have caused complex molecules to develop, or possibly life itself.

科学家们认为，有机物和液体的混合可能会导致复杂分子的发展，甚至可能会导致生命本身。

The search for possible life on Titan will continue when NASA launches its Dragonfly mission to explore the planet in 2026. Dragonfly is a drone, or pilotless aircraft. It is designed to capture images from above Titan as well as to land on the planet to collect data.

美国宇航局启动了2026年探索土卫六的蜻蜓任务，这样对土卫六上潜在生命的寻找将会继续进行。这里的蜻蜓是指一种无人机。它设计用于在土卫六的上空捕获图像，并降落到地表上收集数据。

Dragonfly is not expected to arrive at Titan until 2034. But when it does, Lopes and her team will be excitedly awaiting its findings. "It is not only scientifically important but also really cool - a drone flying around on Titan," she said. "It will be really exciting."

预计蜻蜓要等到2034年才能到达土卫六。但是，一旦它抵达，洛佩斯和她的团队将会兴奋地等待着它的发现。她说：“无人机在土卫六上飞行，这不仅在科学上很重要，也很酷。这会非常令人兴奋。”