After nearly two weeks of delays, a rocket holding Nasa's second Mars rover was launched yesterday on a mission to study whether the red planet ever had enough water to sustain life.

Nasa had until Tuesday to launch Opportunity before Earth and Mars became too far apart. The next chance would be in four years.

A failed battery cell was replaced over the weekend and workers last week reglued in place cork believed to have peeled off the Delta II Heavy rocket during fuelling.

Opportunity and its sister rover, Spirit, which was launched last month, are scheduled to arrive at Mars in January.