The InSight mission, first announced in 2012, is designed to give NASA another scientific tool to help researchers understand the makeup of Mars, how it formed and why it evolved so differently from Earth.
The probe had originally been scheduled to launch this month, but wascalled off in December when scientists were unable to fix a vacuum leak in its prime science instrument.
InSight, which stands for Interior Exploration using Seismic Investigations Geodesy and Heat Transport, now is expected to be launched May 5, 2018 and land on Mars Nov. 26, 2018.
"The science goals of InSight are compelling, and... plans to overcome the technical challenges are sound," John Grunsfeld, associate administrator for NASA's Science Mission Directorate, said in a statement. "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, now in 2018."
Scientists at NASA's Jet Propulsion Laboratory will be redesigning, building and testing a new vacuum enclosure for the Seismic Experiment for Interior Structure, the component that failed in December. The seismometer's main sensors need to be extremely accurate -- able to measure ground movements as small as half the radius of a hydrogen atom.
The vacuum seal is needed to protect the sensor from the harsh conditions on Mars.
NASA said it should have an idea in August of how much the two-year delay will cost.
InSight is comprised of a lander with a robotic arm, two cameras and a thermal probe designed to dig into the Martian surface to calculate the planet's temperature.
Scientists expect the robotic machine to tell them how Mars is cooling, whether the core of Mars is solid or liquid like Earth's, and why Mars' crust is not divided into tectonic plates that drift as they do on Earth.
Mars has been a major focus for NASA scientists. InSight should be joining the Mars rovers Curiosity and Opportunity, as well as the Mars Reconnaissance and Odyssey orbiters in studying the planet.
All of the robotic rovers and orbiters are helping to prepare NASA to send humans to Mars in the 2030s.