The faint seismic signal was detected by the lander's Seismic Experiment for Interior Structure (SEIS) instrument, the first recorded trembling that "appears" to have come from inside the planet, as opposed to being caused by forces above the surface, such as wind.
“InSight’s first readings carry on the science that began with NASA’s Apollo missions,” said InSight principal investigator Bruce Banerdt of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.
“We’ve been collecting background noise up until now, but this first event officially kicks off a new field: Martian seismology!”
NASA confirmed that scientists are still examining the data to determine the exact cause of the signal, as the event was so small that it's unable to provide "solid data on the Martian interior, which is one of InSight's main objectives".
Due to the extremely quiet surface of Mars, the SEIS is able to detect faint rumbles that would comparatively be lost among the noise on Earth, created by oceans and weather.
“We’ve been waiting months for a signal like this,” said Philippe Lognonné, SEIS team lead at the Paris Institute of Earth Physics in France.
“It's so exciting to finally have proof that Mars is still seismically active. We're looking forward to sharing detailed results once we've had a chance to analyse them.”
Quakes on Mars (and the moon) work differently to Earth, as they do not have tectonic plates, and are caused by a continual cooling and contraction process that causes stress to the crust.
“We are delighted about this first achievement and are eager to make many similar measurements with SEIS in the years to come,” said Charles Yana, SEIS mission operations manager at CNES.
You can hear the audio of the "marsquake", here.
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