Washington - The launch of a robot that will delve deep beneath the surface of Mars has been rescheduled for May 5, 2018, US space agency NASA said on Wednesday.The InSight lander was originally set to launch this month but that had to be scrapped because of a problem with a seismometer provided by France's space agency CNES. InSight's primary goal is to study how the solar system's rocky planets, including Earth, formed and evolved.It will help determine whether the core of the red planet is solid or liquid, and why its surface is not made of moving tectonic plates like Earth."The quest to understand the interior of Mars has been a long standing goal of planetary scientists for decades. We're excited to be back on the path for a launch, now in 2018," John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington, said in a statement.Launch dates are based on relative positions of the planets and favourable conditions for missions from Earth to Mars are available a few weeks every 26 months, NASA has said.The robot is now expected to arrive on Mars on November 26, 2018.Three Mars missionsThe delay stemmed from a leak affecting the seismometer device, which measures ground movements as small as the diameter of an atom.It requires a vacuum seal around its three main sensors to withstand the harsh conditions of the Martian environment.Officials were studying the cost of the two-year delay, with an estimate expected in August.The total cost of the mission was budgeted at $675m, of which $525m had been spent by December 2015, according to NASA. NASA is currently working on three Mars missions with the European Space Agency and plans to send another rover to Mars in 2020. A manned mission to Mars is set for the 2030s.