For the first time since landing on Mars in November, NASA's InSight mission has recorded and measured what scientists believe to be a "marsquake."
Martian winds have been recorded on the surface and can be heard on the recording released by the agency . But then, a deeper sound emerges, recorded by the lander's seismometer that was installed on the Red Planet's surface in December.
It's a seismic signal that was recorded April 6, and by all indications, the InSight team believes this sound is a quake from within the planet rather than something on the surface.
The InSight Twitter account shared the recording Tuesday. "Mars, I hear you. I've detected some quiet but distinct shaking on #Mars. The faint rumbles appear to have come from the inside of the planet, and are still being studied by my team. Take a listen."
The data will continue to be studied so that scientists can be sure of the signal's origin.
Smaller seismic signals were detected on Mars in March and April, but researchers aren't sure about their origin, and they are being studied.
Luckily, the Martian surface is quiet, and the seismometer was designed to pick up on smaller rumbles just like this one.
If this had happened on Earth, it probably wouldn't have been detected above the surface vibrations caused by weather and oceans.
"InSight's first readings carry on the science that began with NASA's Apollo missions," said InSight Principal Investigator Bruce Banerdt at NASA's Jet Propulsion Laboratory. "We've been collecting background noise up until now, but this first event officially kicks off a new field: Martian seismology!"
This quake is similar to the ones measured on the moon during the Apollo missions. Between 1969 and 1977, five seismometers installed by Apollo astronauts measured thousands of quakes, shedding light on the moon's seismic activity.
Mars and the moon don't have tectonic plates, which is the cause of quakes on Earth; their quakes are caused by cooling and contraction, which create stress fractures on the crust.
Seismic activity can paint a picture of the interior of a planet and how it was formed, which is one of InSight's main objectives for Mars. However, the new signal is too small and faint to provide a clear picture of the Martian interior.
"We've been waiting months for a signal like this," said Philippe Lognonné, seismometer team lead at the Institut de Physique du Globe de Paris. "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 analyze them."