InSight has just detected its first "marsquake"

In November 2018, NASA Indoor exploration using seismic studies, geodesy and heat transport (InSight) lander landed on Mars. Shortly after, he began to prepare for his scientific operations, which would consist of studying Mars seismology and heat flux to understand how this planet – and all other terrestrial planets in the solar system (such as Earth) – it's formed and evolved. overtime.

With scientific operations well advanced, InSight "listened" to Mars to see what it could learn about its interior structure and composition. A few weeks ago, the mission controllers discovered that the LG's SEIS (Experimental Sismic Experiment for Interior Structure) instrument had detected its most powerful seismic signal (to this day a "marsquake"). This earthquake could say a lot about the red planet and its evolution.

The weak seismic signal, detected by the instrument of seismic experiment for internal structure (SEIS) of the undercarriage, was recorded on April 6, the 128th Martian day (Sol 128) since the landing of the landing gear. This is the first recorded seismic signal that seems to come from the inside of the planet, instead of being caused by something like the wind.

NASA scientists are currently examining the SEIS data to determine the exact cause of the signal, which could come from inside Mars or be caused by a meteorite that crashed on the surface of the planet and that caused ripples through the mantle. On Earth, seismic activity (or "earthquakes") results from an action between tectonic plates, especially along fault lines.

Although Mars and the Moon do not have tectonic plates, they still experience earthquakes, which are largely the result of continuous warming and cooling of their surfaces. This causes expansion and contraction, resulting in enough stress to break the crust. While the new seismic event was too small to provide reliable data on the inside of the Martian site, it gives the mission team an idea of ​​how the seismic activity on Mars works.

For example, the weak nature of this event is similar to that measured by Apollo astronauts in the late 1960s and early 1970s. Apollo 11, NASA astronauts installed a total of five seismometers on the lunar surface, which measured thousands of moonquakes between 1969 and 1977. The data obtained from these sensors allowed scientists to learn a lot about the structure and the internal composition of the Moon.

In this regard, InSight continues a tradition that began with Apollo missions. As Renee Weber, scientist in planetary science at NASA's Marshall Space Flight Center, said in a recent NASA press release:

"We thought Mars would probably be somewhere between Earth and Moon [in terms of seismic activity]. It's still early in the mission, but it's a bit more like the Moon than the Earth. "

Unlike the Earth's surface, which constantly quivers with seismic noise created by oceans and weather conditions, the Martian surface is extremely silent. This allows the SEIS, which was provided by the National Center for Space Studies of France (CNES) and built by the Higher Institute of Aeronautics and Space (ISAE) in Toulouse, to detect low rumors that would go unnoticed on Earth.

As Lori Glaze, director of the Global Science Division at NASA headquarters, said:

"The Martian Sol 128 event is exciting because its size and longer duration match the profile of earthquakes detected on the lunar surface during Apollo missions."

The InSight's SEIS software, which was placed on the surface in December 2018, allows scientists to collect similar data on Mars. And much like the way compositional data on the moon have allowed scientists to hypothesize that the Earth-Moon system has a common origin (the giant impact theory), it is hoped that these data will help to better understand the formation of rock planets in our solar system.

This is the fourth seismic signal detected by the InSight lander, the three previous ones having taken place respectively on March 14 (Sol 105), April 10 (Sol 132) and April 11 (Sol 133). However, these signals were even weaker than the one detected on April 6, which makes them even more ambiguous as to their origins. Here too, the team will continue to study them to try to learn more.

Whatever the cause of the 6 April signal, its detection is an important step for the team. Like Philippe Lognonné, the SEIS team at the Institute of Earth Physics in Paris (IPGP) in France said:

"We have been waiting for months for a signal like this. It's so exciting to finally have the proof that Mars is still seismically active. We look forward to sharing the detailed results once we have had the opportunity to analyze them. "

Of the four events recorded since December, the SEIS team reported that the instrument had exceeded their expectations in terms of sensitivity. "We are delighted with this first achievement and look forward to taking many similar steps with SEIS in the coming years," said Charles Yana, SEIS Mission Operations Manager at CNES.

The lander continues to study the interior of the planet from its location at Elysium Planitia, a plain near the equator of Mars. At present, mission controllers are still trying to figure out how to dislodge the HP3 (Heat and Physical Properties Package) thermal probe, which got stuck in buried rocks in February while she was trying to embed in the soil to measure the temperature.

Be sure to check out this record of the seismic event, courtesy of NASA JPL and the SEIS team:

Further reading: NASA, Nature