In November 2018, NASA. Internal exploration using seismic investigations, geodesy and heat transport (InSight) lander established on Mars. Soon after, he began to prepare for his scientific operations, which would consist of studying the seismology of Mars and its heat flow to learn how this planet and all other terrestrial planets of the Solar System (like Earth) were formed and evolved. through time.
With scientific operations underway, InSight has been "listening" to Mars to see what it can learn about its internal structure and composition. A few weeks ago, mission controllers discovered that the Seismic Experiment for Interior Structure (SEIS) instrument on the lander detected its strongest seismic signal (also known as a "marsquake") to date. This weak tremor could reveal a lot about the Red Planet and how it came to be.
The weak seismic signal, detected by the Seismic Experiment Instrument for Interior Structure (SEIS) of the landing module, was recorded on April 6, or day 128 of Mars (Sun 128) since the vehicle landed. This is the first recorded seismic signal that seems to have originated from inside the planet, instead of being caused by something like the wind.
NASA scientists are now examining the data from SEIS to determine the exact cause of the signal, which may have originated from within Mars or been caused by a meteorite that crashed into the planet's surface and sent waves through of the mantle. On Earth, seismic activity (also known as "earthquakes") is the result of the action between tectonic plates, particularly along fault lines.
While Mars and the Moon do not have tectonic plates, they still experience tremors, which are largely the result of continuous heating and cooling of their surfaces. This causes expansion and contraction, which ultimately results in stress strong enough to break the crust. While the new seismic event was too small to provide solid data on the Martian interior, it is giving the mission team an idea of how seismic activity works on Mars.
For example, the weak nature of this event is similar to that measured by Apollo astronauts in the late 1960s and early 1970s. Beginning with Apollo 11NASA astronauts installed a total of five seismometers on the lunar surface that measured thousands of lunar earthquakes between 1969 and 1977. The data obtained by these sensors allowed scientists to learn a lot about the structure and interior composition of the Moon.
In this sense, InSight continues in a tradition that began with the Apollo missions. As Renee Weber, a planetary scientist at NASA's Marshall Space Flight Center, explained in a recent NASA press release:
"We thought that Mars was probably going to be somewhere between Earth and the Moon. [in terms of seismic activity]. It is still very early in the mission, but it seems a bit more like the Moon than the Earth. "
Unlike the surface of the Earth, which trembles constantly because of the seismic noise created by the oceans and the climate of the planet, the Martian surface is extremely silent. This allows SIX, which was provided by the National Center for Space Studies of France (CNES) and built by the National Superior Institute of Aeronautics and Space (ISAE) of France, to capture weak noises that would go unnoticed on Earth.
As Lori Glaze, director of the Planetary Science Division at NASA headquarters, said:
"The Martian Sun 128 event is exciting because its size and longer duration match the profile of the Moon's earthquakes detected on the lunar surface during the Apollo missions."
The InSight SIX, which was placed on the surface in December 2018, allows scientists to collect similar data on Mars. And just as the way composition data on the Moon allowed scientists to badume that the Earth-Moon system has a common origin (the Giant Impact Theory), these data are expected to shed light on how the they formed the rocky planets of our Solar System.
This is the fourth seismic signal detected by the InSight landing vehicle, the three previous ones took place on March 14 (Sun 105), on April 10 (Sun 132) and on April 11 (Sun 133), respectively. However, these signals were even weaker than those detected on April 6, which makes them even more ambiguous in terms of their origins. Here, too, the team will continue to study them to try to learn more.
Regardless of what caused the April 6 signal, its detection is an exciting milestone for the team. Like Philippe Lognonné, the leader of the SIX team at the Institute of Physics of the Globe of Paris (IPGP) in France, said:
"We've been waiting months for a signal like this, it's so exciting to finally have evidence that Mars is still seismically active, and we're eager to share detailed results once we've had the opportunity to badyze them."
Of the four events recorded since December, the SEIS team has indicated that the instrument has exceeded its expectations in terms of sensitivity. "We are delighted with this first achievement and look forward to many similar measurements with SEIS in the coming years," said Charles Yana, operations manager of the SEIS mission at CNES.
The landing module continues to study the interior of the planet from its place in Elysium Planitia, a plain near the equator of Mars. Currently, mission controllers are still trying to figure out how to dislodge the heat probe from the Heat and Physical Properties Package (HP3), which got stuck in the rock buried in February when it was trying to get on the ground to measure the temperatures there.
Be sure to review this recording of the seismic event, courtesy of NASA JPL and the SEIS team:
Additional readings: NASA, Nature