NASA's scientists believe its lander has detected a first seismic event — the first time a probable seismological tremor has been recorded on a planet other than the Earth and its Moon.
The American space agency's InSight robotic probe picked up the faint rumble on Mars on April 6, the lander's 128th Martian day, or sol.
"We've been collecting background noise up until now, but this first event officially kicks off a new field: Martian seismology!" said InSight Principal Investigator Bruce Banerdt.
Scientists from the NASA Jet Propulsion Laboratory labelled the tremor a "Marsquake".
Three different types of sounds can be heard on the above recording, according to NASA.
There's noise from Martian wind, the seismic event itself, and the spacecraft's robotic arm as it moves to take pictures. These have all been detected as ground vibrations by the spacecraft's seismometer, called the Seismic Experiment for Interior Structure (SEIS).
While several other seismic events have been recorded, they are much more ambiguous than this signal, the space agency said.
This is 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.
One of InSight's main objectives is to provide solid data on the Martian interior of the red planet, but the new seismic event was too small to do this.
While the Earth's surface is quivering constantly from seismic noise created by oceans and weather, Mars' surface is extremely quiet, which allows the SEIS to pick up faint rumbles.
Despite the small scale of this likely "Marsquake", it still marks an exciting milestone for the lander's team.
"We've been waiting months for a signal like this," said Philippe Lognonné, SEIS team lead at the Institut de Physique du Globe de Paris (IPGP) in France. "It's so exciting to finally have proof that Mars is still seismically active."