The first 10 months of data from NASA's Mars Insight mission reveal a new picture of what lies beneath the Red Planet's surface, and it's not all we expected.
Every day small quakes shake the Red Planet. It also has invisible dust devils, weird pulsating magnetic fields and surprisingly flaky top soil, according to the findings reported today in a series of six papers in the journal Nature Geoscience and Nature Communications.
"Mars has offered us many new puzzles and we have to come up with some great new theories to understand all that data," said Sue Smrekar, the mission's deputy principal investigator from NASA's Jet Propulsion Laboratory.
The InSight lander touched down on Mars at the end of 2018 on a volcanic plain known as Elysium Planitia.
In particular, InSight was looking for subtle vibrations caused by internal rumblings, meteorites smashing into the planet or dust devils whipping across the surface.
The larger the quake, the more we learn about the deeper part of Mars.
Some of those quakes confirm Mars is still geologically active below its surface, but the source of others is unknown.
"One thing that is surprising is the large numbers of small events and the lack so far of events larger than magnitude 4," Dr Smrekar said.
Only around 20 quakes between magnitude 3-4 have been detected.
That makes Mars, on average, about as active as Earth in regions that are far from plate boundaries, like Australia.
Dr Smrekar said the quakes typically only lasted for 10 to 20 minutes, which made it challenging to work out where they came from.
Two to three of these events were big enough to be traced to an area called Cerberus Fossae, the volcanically youngest part of the planet 1,600 kilometres to the east of the landing site.
"We can't say exactly what caused those quakes," Dr Smrekar said.
"It could have been motion of magma, it could have been in motion on the fault, or it could have even been flow of water at depth. But it is saying that there is activity still in that region."
The scientists also expected to find around 10 meteorite strikes that would have been responsible for some of the marsquakes, none have been detected so far.
Australian team member Katarina Miljkovic of Curtin University is looking at the impact data in other research.
While Dr Miljkovic said more work was needed to tease out why meteorites aren't appearing in the data as expected, she said confirming that Mars was seismically active was exciting.
Although quakes have been detected on the Moon, "this is this is the first extra-terrestrial planet where we've detected seismic events".
"There is at least one event a day — which is pretty spectacular in itself — and the number of the total number of smaller quakes grows on a daily basis," she said
These shallower quakes could be coming from things at the surface such as changes in atmospheric pressure or dust devils.
But while InSight's weather station has picked up atmospheric vortices and turbulence that varies throughout the day, no dust devils have been seen on the ground, Dr Smrekar said.
The team was also surprised to find that the magnetic field around the lander was 10 times stronger than that observed in space.
"It has to be a patch in the order of 100 kilometres or less in scale, otherwise we'd have seen it from orbit," Dr Smrekar said.
The magnetic field varies in strength throughout the day and sends out a mysterious pulse around midnight.
"We're still not entirely sure what the source of [the pulse] is, but it's certainly telling us about a process going on elsewhere."
"We can see the evidence of impacts everywhere, but what's really interesting is that that top 3 metres isn't consistently the same size range," Professor Benedix commented.
"There seems to be a very thin layer up towards the surface that looks like a crust of some kind that overlays very dusty unconsolidated materials underneath it."
She said the dusty subsoil could have implications for understanding things like how meteor strikes affected the planet.
Dr Smrekar said the scattering of seismic waves in the top soil indicated the upper part of the crust was more broken up by impact craters than people had anticipated.
In turn, the dusty soil could be making it harder to locate events happening now.
"There are probably impacts occurring not so far from us, but the fact that the seismic waves get scattered makes it harder to distinguish an impact," she said.
Dr Smrekar said teams would now spend time reinterrogating the data looking for patterns in seismic activity and collecting new data that is crosschecked using atmospheric and magnetic instruments onboard spacecraft such as Mars Reconnaissance Orbiter and the Mars MAVEN Orbiter.
"It is early in our efforts to interpret these seismic events," she said.
Every day small quakes shake the Red Planet. It also has invisible dust devils, weird pulsating magnetic fields and surprisingly flaky top soil, according to the findings reported today in a series of six papers in the journal Nature Geoscience and Nature Communications.
"Mars has offered us many new puzzles and we have to come up with some great new theories to understand all that data," said Sue Smrekar, the mission's deputy principal investigator from NASA's Jet Propulsion Laboratory.
In particular, InSight was looking for subtle vibrations caused by internal rumblings, meteorites smashing into the planet or dust devils whipping across the surface.
The larger the quake, the more we learn about the deeper part of Mars.
Marsquakes
In its first 10 months of operation, the seismometer picked up 174 events.Some of those quakes confirm Mars is still geologically active below its surface, but the source of others is unknown.
"One thing that is surprising is the large numbers of small events and the lack so far of events larger than magnitude 4," Dr Smrekar said.
Only around 20 quakes between magnitude 3-4 have been detected.
That makes Mars, on average, about as active as Earth in regions that are far from plate boundaries, like Australia.
Dr Smrekar said the quakes typically only lasted for 10 to 20 minutes, which made it challenging to work out where they came from.
Two to three of these events were big enough to be traced to an area called Cerberus Fossae, the volcanically youngest part of the planet 1,600 kilometres to the east of the landing site.
"We can't say exactly what caused those quakes," Dr Smrekar said.
"It could have been motion of magma, it could have been in motion on the fault, or it could have even been flow of water at depth. But it is saying that there is activity still in that region."
The scientists also expected to find around 10 meteorite strikes that would have been responsible for some of the marsquakes, none have been detected so far.
Australian team member Katarina Miljkovic of Curtin University is looking at the impact data in other research.
While Dr Miljkovic said more work was needed to tease out why meteorites aren't appearing in the data as expected, she said confirming that Mars was seismically active was exciting.
Although quakes have been detected on the Moon, "this is this is the first extra-terrestrial planet where we've detected seismic events".
"There is at least one event a day — which is pretty spectacular in itself — and the number of the total number of smaller quakes grows on a daily basis," she said
These shallower quakes could be coming from things at the surface such as changes in atmospheric pressure or dust devils.
Invisible dust devils and weird magnetic fields
Mars' massive dust storms have been observed from space.But while InSight's weather station has picked up atmospheric vortices and turbulence that varies throughout the day, no dust devils have been seen on the ground, Dr Smrekar said.
The team was also surprised to find that the magnetic field around the lander was 10 times stronger than that observed in space.
"It has to be a patch in the order of 100 kilometres or less in scale, otherwise we'd have seen it from orbit," Dr Smrekar said.
The magnetic field varies in strength throughout the day and sends out a mysterious pulse around midnight.
"We're still not entirely sure what the source of [the pulse] is, but it's certainly telling us about a process going on elsewhere."
Flaky top soil
The magnetic and seismic data also revealed amazing detail about the top layer of soil directly underneath the lander, noted Gretchen Benedix of Curtin University.
"We can see the evidence of impacts everywhere, but what's really interesting is that that top 3 metres isn't consistently the same size range," Professor Benedix commented.
"There seems to be a very thin layer up towards the surface that looks like a crust of some kind that overlays very dusty unconsolidated materials underneath it."
She said the dusty subsoil could have implications for understanding things like how meteor strikes affected the planet.
In turn, the dusty soil could be making it harder to locate events happening now.
"There are probably impacts occurring not so far from us, but the fact that the seismic waves get scattered makes it harder to distinguish an impact," she said.
Dr Smrekar said teams would now spend time reinterrogating the data looking for patterns in seismic activity and collecting new data that is crosschecked using atmospheric and magnetic instruments onboard spacecraft such as Mars Reconnaissance Orbiter and the Mars MAVEN Orbiter.
"It is early in our efforts to interpret these seismic events," she said.
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