NASA announced Wednesday that it will attempt to launch its InSight mission to Mars in 2018, two years after its original launch date, after engineers discovered problems with the spacecraft's seismometer system. The decision is a win for Mars scientists because there had been some concern that NASA would have to cancel the mission due to cost overruns.

"The science goals of InSight are compelling," said John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington. "The quest to understand the interior of Mars has been a longstanding goal of planetary scientists for decades. We're excited to be back on the path for a launch."

The seismometer itself worked fine, but several times during the last summer and fall engineers found a leak in the 22cm sphere that creates a vacuum so that the instrument can function on the harsh surface of Mars. Their temporary fixes didn't address the problem. Now NASA and the French seismometer manufacturer Centre National d'Études Spatiales believe they have found a permanent fix for the recurring leak.

NASA says it will have a firm estimate of the delay's cost by August, but one planetary science source pegged the delay in the neighborhood of $150 million. It's not clear what programs in NASA's planetary science program might suffer from the cost overruns of InSight, budgeted at a maximum of $675 million.

The InSight mission has been designed to provide a much better view of the history of Mars, particularly around its interior structure and the forces that shaped the formation of rocky planets like Earth and Mars in the inner Solar System.