Marsquake is official. The Mars InSight Lander of the National Aeronautics and Space Administration detects a tremor in the red planet for the first time.
The lander's Seismic Experiment for Interior Structure instrument was able to record a weak seismic signal on April 6, which is the vehicle's 128th Martian day, or sol. NASA said this is the first time that a tremor seem to have originated from the interior of Mars, instead of from external factors, such as the wind. Experts are still investigating the available information to determine where exactly the tremor came from.
"InSight's first readings carry on the science that began with NASA's Apollo missions," says Bruce Banerdt, InSight Principal Investigator of NASA's Jet Propulsion Laboratory. He adds that the team has been gathering background noise up until now, but this pioneer event officially opens a new horizon, which is Martian seismology.
Earthquake Versus Marsquake
The new seismic signal detected in Mars is considered too small to give strong data about the internal properties of the planet, which is actually one of InSight's main goals. The surface of Mars is really quiet paving the way for SEIS to detect faint activity. Earth, on the other hand, is vibrating constantly from seismic noise generated by oceans and the weather. If a tremor like the one detected by the InSight happens in Southern California, it will just get lost among the other different small quivers that occur daily.
Earthquakes happen on faults produced by the movement of tectonic plates. Mars and the moon do not have tectonic plates. The quakes that occur in these places are caused by the continuous process of cooling and contraction that result in stress. Such stress builds over time and subsequently breaks the crust, causing a quake.
Another difference between earthquake and marsquake is the mechanism by which they are detected. On Earth, devices that measure seismic activity are usually sealed in underground vaults to keep them away from the effects of weather and temperature. On Mars, SEIS has a number of innovative insulating covers, such as JPL's Wind and Thermal Shield, to protect against extreme changes in temperature and high winds.
In Comparison To The Apollo Missions
Lori Glaze, director of NASA Headquarters' Planetary Science Division thinks the Martian Sol 128 event is similar to the moonquakes detected during the Apollo missions. She says the size and longer duration of the recent event and the Apollo missions are comparable.
During the Apollo missions, the astronauts set up five seismometers that recorded thousands of quakes on the moon from 1969 to 1977. The recorded data enabled scientists to discover that different things can alter the speed of seismic waves, enabling them to use these waves to study the internal parts of the moon.
SEIS, which was installed on the Martian surface on Dec. 19, 2018, is said to provide the same information about Mars. By studying what's inside Mars, scientists are able to discover how rocky worlds, such as the Earth and moon, formed.
Results Beyond Expectations
Aside from the Sol 128 event, SEIS was already able to record other seismic signals on March 14 (Sol 105), April 10 (Sol 132) and April 11 (Sol 133). The earlier tremors were more faint and obscure in origin. The team will keep on working to delve into what really caused the quakes. Regardless of cause, they consider Sol 128 as a significant milestone.
"We've been waiting months for a signal like this," says Philippe Lognonné, SEIS team lead from France's Institut de Physique du Globe de Paris. He adds that it is exciting to finally have evidence that Mars is still active, seismic-wise. His team is looking forward to share other information to the public as their investigation advances.
Centre National d'études Spatiales is the French space agency that supplied SEIS, while the Swiss Federal Institute of Technology led the detection of Mars' first tremor.
Overall, the team behind SEIS believes the instrument performed beyond expectations. Charles Yana, manager of SEIS mission operations at CNES, says they are psyched about this first achievement, and the similar measurements that are about come in the following years.