Astronomy Picture of the Day

Explanation: Arachnoids are large structures of unknown origin that have been found only on the surface of Venus. Arachnoids get their name from their resemblance to spider-webs. They appear as concentric ovals surrounded by a complex network of fractures, and can span 200 kilometers. Radar echoes from the Magellan spacecraft that orbited Venus from 1990 to 1994 built up this image. Over 30 arachnoids have been identified on Venus, so far. The Arachnoid might be a strange relative to the volcano, but possibly different arachnoids are formed by different processes.

蜘蛛狀結構是一種起源不明的大型構造，而且只發現於金星的表面上。 蜘蛛狀物體則是得名於其外觀形似蜘蛛網。 它們呈同心橢圓形，周圍有複雜的裂縫網絡，跨幅可達200公里。 這幅圖像，建構自1990年至1994年間繞行金星的麥哲倫號太空船所回傳的雷達回波數據。 截目前為止，已在金星上找到30多個蜘蛛狀結構。 蜘蛛狀結構可能是火山的怪親戚，不過，不同形狀的蜘蛛狀結構，可能形成於不同的過程。