Mars may look dry and dusty from the outside, but it has a surprisingly vibrant inner life, according to new findings from NASA's quake-hunting InSight mission.
The lander, which touched down on the red planet 15 months ago, has detected plenty of seismic activity, an unexpectedly strong local magnetic field and around 10,000 whirlwinds passing over the Martian surface.
The findings, published Monday in a suite of six papers in the journals Nature Geoscience and Nature Communications, will help scientists unlock the secrets of Mars' interior and understand why it looks so different from Earth.
"What these results really are showing us is that Mars is an active planet today," said Bruce Banerdt, the mission's principal investigator, based at NASA's Jet Propulsion Laboratory [JPL] in La Canada-Flintridge, California, and a co-author of the new studies.
InSight is situated in a roughly 25-metre-wide impact crater in western Elysium Planitia, a volcanic plain whose surface material ranges in age from 3.7 billion to just 2.5 million years old.
About 1600 kilometres away lies Cerberus Fossae, a volcanic region full of faults, evidence of old lava flows and signs that liquid water once ran on the surface.
"Anything that's been active in the last couple million years could be active today, especially at depth," Banerdt said.
The lander is equipped with a dome-covered seismometer to measure quakes in Mars' upper layers. The quake-sensing instrument also comes with a small entourage of magnetic pressure, wind and temperature sensors.
The seismometer picked up 174 marsquakes through September 30, including more than 20 measuring magnitude 3 to magnitude 4.
These shakers wouldn't necessarily have felt like magnitude 3 or 4 temblors on Earth because they originated far deeper than such quakes typically do on this planet.
In general, tectonic activity on Mars is caused by the upper layers of the planet deforming and cracking as its interior cools and shrinks.
But there are many different potential causes of individual marsquakes, and scientists said they'd need to catch more of them - particularly the larger-magnitude ones - to figure out the cause of any single event. So far, the larger quakes seem to be less frequent than scientists expected, and no "big ones" over magnitude 4 have appeared.
"Right now, we've got a lot more data than we have conclusions, and we're still trying to get our arms around what Mars is telling us," Banerdt said. "This is an entire new world of processes for us."
On Mars, he added, "we really are in the same situation that geophysicists were (in) for the Earth back in the early 1900s ... We're seeing these wiggles, we're using the best analysis tools we have, but it's still a very mysterious situation."
Still, two of the marsquakes were big enough to be traced to Cerberus Fossae, and it's possible that a pocket of magma deep beneath the surface might have had something to do with them.
Scientists think ancient Mars once had a thicker atmosphere that could have encapsulated clouds in the sky and liquid water on the surface - an almost Earth-like environment with the potential to support life.
Even with the relatively paltry atmosphere that remains, the Martian surface has proved surprisingly dynamic, scientists said. InSight's instruments have picked up evidence of around 10,000 whirlwinds that might be termed dust devils - if they had whipped up enough dust to be seen as well as felt.
It will take another Earth year or so of readings for InSight to gather more clues about the planet's inner and outer dynamics, NASA scientists said.
Australian Associated Press