since 从句的时态理解

The surface feature has remained in popular culture since the image of the "Face on Mars" was known.

When this photograph was taken in 1976, many took it to be the proof that alien life existed on Mars.

......

Some people thought the "Face on Mars" was the evidence that someone had landed on Mars and built the "face" to let us know that.

请教老师：

(1) since the image of...was known 为什么不是since the image of..."has been" known 呢？

(2) 如何理解这里2句proof that...和evidence that...是同位语从句？感觉从逻辑，句意上很难理解？老师能解释一下吗？

谢谢老师。

1.since 从句通常表示从过去某个时间点开始，所以用过去式。但也有用完成时的时候，相对少见一些。

2. 逻辑很清楚呀。把照片当作火星有过外星生命的证据，这有什么难理解的呢？

好题 -

擅长：英语 | 采纳率 52% | 回答于 2022-03-15 13:07

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