We are facing an unknown purpose unknown quantity.

们常常是对着一个未知数而前进。

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Now researchers estimate that nearly ten times as many such structures-of unknown purpose-may exist undetected under the Amazon's forest cover.

研究人员估计有近十倍于已发现的这种结构(不知处于何种目的建造)存在于未探测的亚马逊森林覆盖下。

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The researchers behind the January study, though, estimated that nearly ten times as many such structures—of unknown purpose—may exist undetected under the Amazon's forest cover.

研究人员通过1月份的调查认为，在亚马逊森林的覆盖下，估计还有比已发现的地面结构大十倍之多的地方还未被检测出来。

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It was once thought the hill was a burial mound, but no grave has been found and its purpose is unknown.

BBC: Prehistoric Silbury Hill 'was built in layers'

The purpose, as Newman points out is to discover the unknown: a Trojan, or bot that has evaded detection and is sitting on some infected host.

FORBES: Uncovering the unknown threat via beaconing detection

The purpose of the current Okeanos Explorer expedition is to help reduce that large unknown, by mapping and imaging features and creatures that may never have been seen before.

WHITEHOUSE: Watch Live: Be a Virtual Ocean Explorer