NASA investigators think that the Mars InSight Lander has recorded a seismic event, or “marsquake”.
The likely quake – in the form of a faint rumble detected by the lander’s Seismic Experiment for Interior Structure (SEIS) instrument – was detected on April 6, but the news was kept under wraps for a couple of weeks while the readings were analysed.
The event was too small and too brief to provide any useful information about the interior of the planet, but was nevertheless highly significant.
“We’ve been collecting background noise up until now,” says InSight principal investigator Bruce Banerdt of NASA’s Jet Propulsion Laboratory (JPL) in California, US, “but this first event officially kicks off a new field: Martian seismology!”
The quake was detected as InSight entered Martian day number 128 of its mission. Its detection highlights one of the principle differences between the geology of Earth and Mars.
Beneath its surface, Mars is very quiet, allowing the SEIS instrument to pick up extremely small signals. Earth geology, by contrast, is very noisy, vibrating all the time, even in the absence of tectonic shifts, because of the forces exerted by oceans and weather systems. A tremble the size of the latest Mars one would have been effectively inaudible.
“We’ve been waiting months for a signal like this,” says SEIS mission member Philippe Lognonné, from 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. We’re looking forward to sharing detailed results once we’ve had a chance to analyse them.”
Unlike Earth, Mars does not have tectonic plates. It’s thought that its quakes arise because the interior of the planet continually cools and contracts, creating stress.
A second set of InSight instruments, known as Very Broad Band sensors, detected other possible quakes on March 14, April 10 and April 11. However, the signals were very weak and, so far, researchers have not been able to unambiguously identify them as quakes.
Another member of the SEIS, Neil Bowles from the UK’s University of Oxford, is already looking forward to the next Martian rumble.
“Seeing the first likely ‘marsquake’ is really exciting and it shows the fantastic performance of the SEIS instrument,” he says.
“We can now start to characterise the types of signals we see on Mars to try and understand how this relates to the structure of planet.”