The space administration's lander probe, which is designed to dig as far as five meters below the surface and measure heat coming from inside the planet, hit a snag after encountering what scientists suspect is a "rock or some gravel", The Associated Press reported.
The drilling instrument, dubbed 'the mole', first encountered trouble last week when it struck what appeared to be a couple of stones, prompting developer Astronika to lament that "the Mars environment is not very favorable to us".
The probe only managed to burrow between 18 centimeters and about 50 centimeters — far short of the first dig's goal.
Despite being designed to push rocks aside or "wend its way around them", NASA instrument lead Tilman Spohn said it had "continued to work against some resistance without clear evidence for progress".
"The team has therefore decided to pause the hammering for about two weeks to allow the situation to be analyzed more closely and jointly come up with strategies for overcoming the obstacle," he wrote in an online logbook.
"In the meantime, we are planning on carrying out thermal conductivity measurements for the first time on Mars.
The Mars InSight lander touched down on the dusty Red Planet in November last year after sailing 548 million kilometers over a six-month voyage through deep space.
InSight will spend 24 months using seismic monitoring and underground temperature readings to unlock mysteries about how Mars formed and, by extension, the origins of the Earth and other rocky planets of the inner solar system.
But the spacecraft has no life-detecting capability.
That will be left to future rovers, such as NASA's Mars 2020 mission, which will collect rocks that will eventually be brought back to Earth and analyzed for evidence of ancient life.