An air leak in one of the instruments of the Interior Exploration Using Seismic Investigations, Geodesy and Heat Transport (InSight) spacecraft forced NASA to delay its flight to Mars two more years.

According to The Associated Press, the instrument was scheduled to head to its launch site in Southern California next month ahead of a launch toward Mars in March. The instrument in question is the Seismic Experiment for Interior Structure (SEIS), which came from the French Space Agency (CNES).

"The seismometer is the prime science payload that will help answer questions about the interior structure and processes within the deep Martian interior. The SEIS instrument has three high-sensitivity seismometers enclosed in a sealed sphere," NASA stated in a news release. "The seismometers need to operate in a vacuum in order to provide exquisite sensitivity to ground motions as small as the width of an atom. After the final sealing of the sphere, a small leak was detected, that would have prevented meeting the science requirements once delivered to the surface of Mars.

"The CNES/JPL team is currently working to repair the leak, prior to instrument integration and final environmental tests in France before shipping to the United States for installation into the spacecraft and launch."

NASA had to delay the launch by two years because the Earth's alignment needs to be aligned properly with Mars, Reuters noted. Unlike the rovers NASA previously landed on Mars, the InSight probe would stay in one place on the Red Planet's surface and detect seismic activity and subsurface heat.