“It’s great to finally have a sign that there’s still seismic activity on Mars,” said Philippe Lognonne, a researcher at Paris’ Institut de Physique du Globe. “We’ve waited for our first Martian quake for months.” Scientists said Tuesday they might have detected the first known seismic tremor on Mars in a discovery that could shed light on the ancient origins of Earth’s neighbor.
A dome-shaped probe known as SEIS landed on the surface of Mars in December after hitching a ride on NASA’s InSight spacecraft. With InSight’s landing at Elysium Planitia, NASA has successfully soft-landed a vehicle on the Red Planet eight times. Its instruments measure surface vibrations caused by weather but are also capable of detecting movement from deep within the planet—so called “marsquakes”—or those caused by meteorite impacts.
“In some ways, InSight is like a scientific time machine that will bring back information about the earliest stages of Mars’ formation 4.5 billion years ago,” said JPL’s Bruce Banerdt, principal investigator. “It will help us learn how rocky bodies form, including Earth, its moon, and even planets in other solar systems.”
According to Banerdt, the data that the Insight spacecraft will collect will “prime NASA on all the geological processes” that have persisted on Mars for the past billions of years.
“If you were a Martian coming to explore Earth’s interior like we are exploring Mars’ interior, it wouldn’t matter if you put down in the middle of Kansas or the beaches of Oahu,” said Banerdt. “While I’m looking forward to those first images from the surface, I am even more eager to see the first data sets revealing what is happening deep below our landing pads. The beauty of this mission is happening below the surface. Elysium Planitia is perfect.” The 81-mile long, 17-mile-wide (130-kilometer-long, 27-kilometer-wide) landing ellipse is on the western edge of a flat, smooth expanse of lava plain.
The French space agency Cnes, which operates SEIS, said it had detected “a weak but distinct seismic signal” from the probe into its formation billions of years ago.
According to Banerdt, the quake detection “marks the birth of a new discipline: Martian seismology.”
The new seismic event was too small to provide solid data on the Martian interior. The Martian surface is extremely quiet, allowing SEIS, InSight’s specially designed seismometer, to pick up faint rumbles. In contrast, Earth’s surface is quivering constantly from seismic noise created by oceans and weather. An event of this size in Southern California would be lost among dozens of tiny crackles that occur every day.
“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,” said Lori Glaze, Planetary Science Division director at NASA Headquarters.
NASA’s Apollo astronauts installed five seismometers that measured thousands of quakes while operating on the Moon between 1969 and 1977, revealing seismic activity on the Moon. Different materials can change the speed of seismic waves or reflect them, allowing scientists to use these waves to learn about the interior of the Moon and model its formation. NASA currently is planning to return astronauts to the Moon by 2024, laying the foundation that will eventually enable human exploration of Mars.
InSight’s seismometer, which the lander placed on the planet’s surface on Dec. 19, 2018, will enable scientists to gather similar data about Mars. By studying the deep interior of Mars, they hope to learn how other rocky worlds, including Earth and the Moon, formed.
Three other seismic signals occurred on March 14 (Sol 105), April 10 (Sol 132) and April 11 (Sol 133). Detected by SEIS’ more sensitive Very Broad Band sensors, these signals were even smaller than the Sol 128 event and more ambiguous in origin. The team will continue to study these events to try to determine their cause. Regardless of its cause, the Sol 128 signal is an exciting milestone for the team.
Most people are familiar with quakes on Earth, which occur on faults created by the motion of tectonic plates. Mars and the Moon do not have tectonic plates, but they still experience quakes – in their cases, caused by a continual process of cooling and contraction that creates stress. This stress builds over time, until it is strong enough to break the crust, causing a quake.
Detecting these tiny quakes required a huge feat of engineering. On Earth, high-quality seismometers often are sealed in underground vaults to isolate them from changes in temperature and weather. InSight’s instrument has several ingenious insulating barriers, including a cover built by JPL called the Wind and Thermal Shield, to protect it from the planet’s extreme temperature changes and high winds.
SEIS has surpassed the team’s expectations in terms of its sensitivity. The instrument was provided for InSight by the French space agency, Centre National d’Études Spatiales (CNES), while these first seismic events were identified by InSight’s Marsquake Service team, led by the Swiss Federal Institute of Technology.
The team said they were still working to confirm the cause of the tremor, picked up on April 6, and ensure it came from the planet’s interior rather than wind or noise distortion. It said three other similar but weaker signals of tremors had been picked up by the apparatus.