时差N小时:火星上的海洋

Don: Hey, Yaël, Have you heard? We've discovered two new oceans?

嘿，Yaël，你听说了吗?我们已经发现了两块新大洋。

Yaël: Where?

在哪啊?

D: On Mars. Well, they aren't there any longer, but they were there a few billion years ago.

在火星上。虽然现在不在那儿了，但几十亿年前一直都在。

Y: I thought scientists weren't sure if Mars had oceans or not.

我想科学家们还是不确定火星上到底有没有海洋。

D: They weren't. The Mars Opportunity Rover found sulfates and other salts in the soil thatwere left behind when standing water evaporated. It also discovered cross-bedding in the soilwhich was created by water ripples, and tiny mineral deposits called blueberries that onlyappear if water is present. The northern lowlands of Mars looked like there might have been anocean there, but there wasn't definite proof.

恩，不确定。机遇号火星探测器在土壤中发现了水分长期挥发后所留下的硫酸盐和其它的盐类。同时还在土壤中发现了水波所形成的交错层，以及称之为蓝莓的小型矿床，而这种矿床只有在存在水的地方才产生。火星的北部低地看起来像是曾经有过一片海洋，但还没有发现确凿的证据。

Y: So, what has changed their minds?

那又是什么让科学家们改变了想法呢?

D: Gamma Ray evidence.

是伽马射线。

Y: That sounds exciting.

听起来真令人兴奋啊。

D: It is. The Mars Odyssey spacecraft had a gamma-ray spectrometer onboard that coulddetect elements buried as much as a third of a meter, or thirteen inches, below the soil.Scientists used the spectrometer to measure the amount of potassium, thorium, and ironabove and below what they thought to be the shoreline of ancient oceans. They expected to seelow concentrations above the shoreline and larger concentrations below. That would indicatethat the elements had been leached out of the soil by the water.

是啊。奥德赛号火星探测器有一个γ射线能谱仪主板，它可以检测到埋藏于地底三分之一或地下13英寸的元素。科学家们利用光谱仪在所推断的远古海洋海岸线附近测量钾、钍、铁的含量。科学家们预测海岸线上的元素浓度较低，而海岸线以下的浓度较高。这将证明那些元素是通过水过滤到土壤中的。

Y: So, what did they find?

那么他们究竟发现了什么呢?

D: They found the shorelines of a younger ocean about ten times the size of the MediterraneanSea, and an older ocean twice that size.

他们发现了一个较新，海岸线大约是地中海的10倍的海洋痕迹，和一个年代比较久远相当于地中海海岸线两倍的海洋痕迹。

Y: It's too bad those oceans still aren't there.

这些海洋已经不在那儿真是太糟糕了。

D: Yeah. It sure would be a great spot for a cruise.

对啊，如果它们还在那儿，那将是个很适合巡航的地儿。