In November of 2018, the NASA Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander set down on Mars. Shortly thereafter, it began preparing for its science operations, which would consist of studying Mars’ seismology and its heat flow for the sake of learning how this planet – and all the other terrestrial planets in the Solar System (like Earth) – formed and evolved over time.
With science operations well-underway, InSight has been “listening” to Mars to see what it can learn about its interior structure and composition. A few weeks ago, mission controllers discovered that the lander’s Seismic Experiment for Interior Structure (SEIS) instrument detected its strongest seismic signal (aka. a “marsquake”) to date. This faint quake could reveal much about the Red Planet and how it came to be.
The faint seismic signal, detected by the lander’s Seismic Experiment for Interior Structure (SEIS) instrument, was recorded on April 6th, or the 128th Martian day (Sol 128) since the lander touched down. This is the first recorded seismic signal that appears to have originated from inside the planet, as opposed to being caused by something like wind.
NASA scientists are now examining the SEIS data to determine the exact cause of the signal, which may have originated from inside Mars or been caused by a meteorite crashing into the planet’s surface and sending ripples through the mantle. On Earth, seismic activity (aka. “earthquakes”) are the result of action between tectonic plates, particularly along fault lines.
While Mars and the Moon do not have tectonic plates, they still experience quakes, which are largely the result of the continual heating and cooling of their surfaces. This causes expansion and contraction, which eventually 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 on Mars works.
For instance, the faint nature of this event is similar to those measured by the Apollo astronauts during the late 1960s and early 1970s. Beginning with Apollo 11, NASA astronauts installed a total of five seismometers on the lunar surface that measured thousands of moonquakes between 1969 and 1977. The data obtained by these sensors allowed scientists to learn a great deal about the Moon’s interior structure and composition.
In this respect, InSight is carrying on 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 Mars was probably going to be somewhere between Earth and the Moon [in terms of seismic activity]. It’s still very early in the mission, but it’s looking a bit more Moon-like than Earth-like.”
Unlike Earth’s surface, which is constantly quivering from seismic noise created by the planet’s oceans and weather, the Martian surface is extremely quiet. This allows SEIS, which was provided by France’s National Center for Space Studies (CNES) and built by the French National Higher Institute of Aeronautics and Space (ISAE) in Toulouse, to pick up faint rumbles that would go unnoticed on Earth.
As Lori Glaze, the Planetary Science Division director at NASA Headquarters, said:
“The Martian Sol 128 event is exciting because its size and longer duration fit the profile of moonquakes detected on the lunar surface during the Apollo missions.”
InSight’s SEIS, which it placed on the surface in December of 2018, is allowing scientists to gather similar data about Mars. And much like how composition data on the Moon allowed scientists to hypothesize that the Earth-Moon system has a common origin (the Giant Impact Theory), it is hoped that this data will shed light on how the rocky planets of our Solar System formed.
This is the fourth seismic signal detected by the InSight lander, the previous three having taken place on March 14th (Sol 105), April 10th (Sol 132) and April 11th (Sol 133), respectively. However, these signals were even fainter than the one detected on April 6th which makes them even more ambiguous as far as their origins are concerned. Here too, the team will continue studying them to try to learn more.
Regardless of what caused the April 6th signal, its detection is an exciting milestone for the team. As Philippe Lognonné, the SEIS team lead at the Institut de Physique du Globe de Paris (IPGP) in France, said:
“We’ve been waiting months for a signal like this. 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.”
From the four events recorded since December, the SEIS team has indicated that the instrument has surpassed their expectations in terms of sensitivity. “We are delighted about this first achievement and are eager to make many similar measurements with SEIS in the years to come,” said Charles Yana, the SEIS mission operations manager at CNES.
The lander continues to study the planet’s interior from its spot in Elysium Planitia, a plain near Mars’ equator. At present, mission controllers are still trying to figure out how to dislodge the Heat and Physical Properties Package (HP3) heat probe, which became stuck in buried rock back in February while trying to hammer itself into the ground to measure the temperatures there.
Be sure to check out this recording of the seismic event, courtesy of NASA JPL and the SEIS team: