Bengaluru: Results from a NASA mission on Mars has revealed a planet that is alive with quakes, seismic zones and strange magnetic pulses.
The findings of 10 months of NASA’s InSight lander mission have been described in a set of six papers published Monday in the journals Nature Geoscience and Nature Comminications.
InSight is the first mission dedicated to looking deep beneath the Martian surface. After landing on Mars in November 2018, the lander has been performing extensive investigation of the planet’s surface.
The results, which have surprised scientists, have shown that Mars is seismically active and has regular marsquakes at a strength and frequency between that of the Earth’s and the Moon’s.
The most notable of all findings have been the readings of seismic activity on the planet. The researchers have analysed 174 incidences of quakes from April to September last year.
They had earlier also discovered the first active fault zone on the planet. These are regions where active seismic activity can be expected.
“We’ve finally, for the first time, established that Mars is a seismically active planet,” InSight Principal Investigator Bruce Banerdt, of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, said at a statement Thursday.
“It’s just such a relief to finally be able to stand up and shout, look at all this great stuff we’re seeing,” he added.
An analysis of marsquakes have indicated that water may be present deep within the red planet. Sensors near the lander have also detected thousands of small whirlwinds and strong magnetic signals from rocks underground.
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Seismology on Mars
The strongest quakes on Mars have been found to measure 3 to 4 on the Richter scale. These are not too strong on Earth and quakes measuring 5.5 and above usually cause damage to concrete structures.
Mars does not have active plate tectonics like Earth. When tectonic plates move, stress builds up due to friction. When this stress increases to the point of breaking, seismic waves are released from stored energy that eventually causes earthquakes.
Without a similar mechanism on Mars, it is still a mystery as to what exactly causes seismic activity on the planet. Scientists have so far only predicted that the cooling and contracting action of its magma and rocks causes marsquakes.
They have, however, argued that there is the need for a lot of observation before arriving at a conclusion about seismic activity on Mars.
“As the planet cools, it contracts, and then the brittle outer layers have to fracture in order to sort of maintain themselves on the surface,” Banerdt said. “That’s kind of the long-term source of stresses.”
Researchers have also observed that the frequency of small quakes seem to increase in Mars. From April to September, less than 200 quakes were observed. Since September 2019, there have been over 250. While the researchers aren’t sure what affected the frequency of marsquakes, they suspect it could be seasonal.
The original locations of these quakes have also been inexplicable. Around 150 quakes were shallow and smaller in magnitude, originating and propagating through the crust. The remaining 24 came from deep within the mantle, at different heights, and were stronger.
The origins of two of the largest quakes were traced to Cerberus Fossae, a series of fissures on the surface of the planet that were formed over 10 million years ago. This is the active fault zone which InSight planetary scientists had discovered last year.
Through the Cerberus Fossae, lava and water were likely to have been oozing out to the surface millions of years ago. These might have originated from pockets of magma cooling underneath, and it is possible that some fluids are still underground, said scientists.
InSight also detected a mysterious seismic signal pulsating constantly in the background of the regular quakes. This signal seemed to be independent of the movement of wind on the planet.
The humming sound of the mysterious signal seemed to strengthen when a quake occurred. Scientists are, however, unsure what causes this humming sound — whether it is the planet’s geology or the InSight lander itself.
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Stronger magnetic field
The InSight lander also discovered that the magnetic field surrounding the lander is 10 times stronger than what was earlier expected.
Earth’s magnetic field is formed because of our rotating core — the molten iron core rotates steadily for 3,000 km underground, causing it to behave like a dynamo.
This geodynamo generates a global magnetic field which surrounds the Earth and protects it from the Sun’s harmful radiation. The magnetic field is also responsible for protecting the atmosphere and the environment, and without it, Earth might lose its atmosphere to space like the Mars has.
Mars also had a geodynamo, but scientists suspect that it had stopped rotating billions of years ago. There have only been lingering remains of Martian magnetism, primarily found in rocks. Data from InSight, however, pointed to a much stronger magnetic field than expected.
Scientists also found a pulsating and varying magnetic field on top of the planetary field. The InSight lander has detected magnetic pulses that seemed to throb in variation.
Magnetic variation around a planet isn’t uncommon — during the day, on Earth, solar radiation interacts with its magnetic field and releases charged particles via wind movement, generating magnetic and electric currents. So the field is stronger during the day and is comparatively weaker at night.
The same mechanism also seems to be working on Mars, something which the scientists didn’t expect to find. The Martian field, however, was found to have shorter periods of variation, lasting only a few hours and occurring sometimes at dawn or dusk, but mostly at midnight.
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Other measurements
InSight also has a mole that is expected to dig underground but Martian dirt proved to be more slippery than anticipated. This has prevented the mole’s burrowing system from working efficiently.
Engineers have tried multiple things to get the mole working but have not been successful. In the next two months, scientists are expected to focus on getting the mole to dig underground efficiently.
InSight is also monitoring the Martian weather, collecting pressure and temperature data. Data on pressure is collected many times per second to record variations, while temperature is collected once in many seconds. This will help them understand the sounds coming from under the planet’s surface better.
The InSight mission is expected to advance our understanding of the evolution of Mars and its current processes.
“This is really going to, I think, revolutionise our understanding of the interaction of the atmosphere with the surface of Mars,” added Banerdt. “That’s one of the things that’s really going to open up a whole new window of research on Mars.”
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