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Back in July 1965,the Mariner Four space Probe transmitted thefirst close-up pictures of Mars and convinced many people thatMars was as dead as our own moon.Two later space probesseemed to confirm this.But then,in 1971,Mariner Nine raised hopes once again thatthere could be life on the planet—or at least that life might oncehave existed there.Pictures revealed the existence of a volcano—