The sound was detected by NASA's Insight Lander, a robot spacecraft that's now sitting on the Martian surface. The sound was detected on April 6, 2019.
Three distinct kinds of sounds can be heard, all of them detected as ground vibrations by the spacecraft's seismometer: noise from Martian wind, the quake itself, and the spacecraft's robotic arm as it moves to take pictures.
InSight heard the "marsquake" using a French-built instrument that contains three extremely sensitive seismometers nestled inside a dome to protect them from the wind, Nature magazine said.
“We’ve been waiting months for a signal like this,” said French seismologist Philippe Lognonné. "It's so exciting to finally have proof that Mars is still seismically active."
Science magazine reported that the quake is so tiny that it would never be detected on Earth amid the background sounds of waves and wind.
As InSight’s two-year mission continues, larger quakes will likely be discovered, Lognonné said. “We’re starting to have many small quakes,” he said. By the end of the mission, he told Science, “we’ll have a super big quake.”
This is not the first quake detected away from Earth: NASA’s Apollo astronauts installed five seismometers that measured thousands of quakes while operating on the moon between 1969 and 1977.