InSight has recorded about 450 marsquakes to date.
This image, the second selfie
captured by NASA's InSight Mars lander, is a mosaic of 14 photos taken
between March 15 and April 11, 2019.
(Image: © NASA/JPL-Caltech)
Mars may be cold and dry, but it's far from dead.
The first official science results from NASA's quake-hunting
InSight Mars lander just came out, and they reveal a regularly roiled world.
"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 during a teleconference with reporters Thursday (Feb.
20).
Related: Mars InSight in photos: NASA's mission to probe Martian core
Martian seismicity falls between that of
the moon and that of Earth, Banerdt added.
"In
fact, it's probably close to the kind of seismic activity you would
expect to find away from the [tectonic] plate boundaries on Earth and
away from highly deformed areas," he said.
https://www.space.com/nasa-insight-lander-mars-seismically-active.html?fbclid=IwAR2NNzs2dgXc-2K-sXS2vUnruDiMO9QmeA7zUHzs_JkMmekJu_eZjaHbIjA&jwsource=cl
Probing the Martian subsurface
InSight touched down
near the Martian equator in November 2018, kicking off a two-year, $850
million mission to probe the Red Planet's interior in unprecedented
detail.
The stationary lander carries two main science
instruments to do this work: a supersensitive suite of seismometers and a
burrowing heat probe dubbed "the mole," which is designed to get at
least 10 feet (3 meters) below the Red Planet's surface.
Analyses of marsquake and heat-transport measurements will allow the mission team to construct a detailed, 3D map of
the Martian interior,
NASA officials have said. In addition, InSight scientists are using
radio signals beamed from the lander to track how much Mars wobbles on
its axis over time. This information will help researchers determine how
big and dense the planet's core is. (The mission's full name — Interior
Exploration using Seismic Investigations, Geodesy and Heat Transport —
references these various lines of investigation.)
Overall,
InSight's observations will help scientists better understand how rocky
planets such as Mars, Earth and Venus form and evolve, mission team
members have said.
The mission's initial science returns, which were published today (Feb. 21) in six papers in the journals
Nature Geoscience and
Nature Communications, show that InSight is on track to meet that long-term goal, Banerdt said. (We have gotten a
taste of these results over the past year or so, however, as mission team members have released some findings in dribs and drabs.)
Related: NASA's Mars InSight lander: 10 surprising facts
https://videos.space.com/m/uxwPf3tt/how-are-marsquakes-monitored?list=9wzCTV4g
lots of quakesThe new studies cover the first 10 months of InSight's tenure on Mars, during which the lander detected 174 seismic events.
These
quakes came in two flavors. One hundred and fifty of them were shallow,
small-magnitude tremors whose vibrations propagated through the Martian
crust. The other 24 were a bit stronger and deeper, with origins at
various locales in the mantle, InSight team members said. (But even
those bigger quakes weren't that powerful; they landed in the magnitude 3
to 4 range. Here on Earth, quakes generally must be
at least magnitude 5.5 to damage buildings.)
That
was the tremor tally through September 2019. InSight has been busy
since then as well; its total quake count now stands at about 450,
Banerdt said. And all of this shaking does indeed originate from Mars
itself, he added; as far as the team can tell, none of the vibrations
were caused by meteorites hitting the Red Planet. So, there's a lot
going on beneath the planet's surface.
But that activity is quite different from what we're used to on Earth, where most quakes are caused by
tectonic plates
sliding against, over or under each other. Mars doesn't have active
plate tectonics, the researchers said, so both types of quakes are
caused by the long-term cooling of the planet since its formation 4.5
billion years ago.
"As the planet cools, it contracts, and then
the brittle outer layers then 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."
And some Martian locales are more
stressed than others. One particularly active region is the Cerberus
Fossae fracture system, which lies about 1,000 miles (1,600 kilometers)
east of InSight's Elysium Planitia landing site.
The mission team
traced two of the largest detected marsquakes to Cerberus Fossae, which
"contains faults, volcanic flows and liquid water outflow channels with
ages as recent as 2-10 Ma [million years ago], and possibly younger from
impact crater counts," Banerdt and his colleagues wrote in
one of the new studies.
"So,
it's possible that there's actual magma at depth that's cooling,"
InSight deputy principal investigator Sue Smrekar, also of JPL, said
during Thursday's teleconference. That cooling would lead to the
contraction of the magma chamber, causing deformation of the crust, she
added.
But Smrekar stressed that this is a hypothesis, not a
definitive determination of what's going on at Cerberus Fossae. Indeed,
though mission team members think they understand Martian seismicity in
broad strokes, they're still trying to nail down how it works in detail.
Related: 7 biggest mysteries of Mars
https://www.space.com/nasa-insight-lander-mars-seismically-active.html?fbclid=IwAR2NNzs2dgXc-2K-sXS2vUnruDiMO9QmeA7zUHzs_JkMmekJu_eZjaHbIjA
Many insights
A
wealth of information can be gleaned from InSight's quake measurements.
For example, analyses of how the seismic waves move through the Martian
crust suggest there are small amounts of water mixed in with the rock,
mission team members said.
"Our data is consistent with a crust which has some moisture in it, but we can't say one way or the other whether there [are]
large underground reservoirs of water at this point," Banerdt said.
The
new papers report a variety of other discoveries as well. For example,
InSight is the first mission ever to tote a magnetometer to the Martian
surface, and that instrument detected a local magnetic field about 10
times stronger than would be expected based on orbital measurements.
(Mars lost its global magnetic field billions of years ago, however.
This allowed solar particles to strip away the once-thick
Martian atmosphere, which spurred the planet's transition from a relatively warm and wet world to the cold desert it is today.)
InSight
is also taking a wealth of weather data, measuring pressure many times
per second and temperature once every few seconds, Banerdt said. This
information helps the mission team better understand environmental noise
that could complicate interpretations of the seismic observations, but
it also has considerable stand-alone value.
"This is really going
to, I think, revolutionize our understanding of the interaction of the
atmosphere with the surface of Mars," Banerdt said. "That's one of the
things that's really going to open up a whole new window of research on
Mars."
ole updateNot
everything has gone smoothly for InSight, however. Notably, the mole
has been unable to get down to its prescribed depth because the
Martian dirt is proving more slippery
than mission team members had anticipated. (The mole's self-hammering
burrowing system requires a certain amount of friction to work.)
The
mission team has tried several strategies to get the mole moving,
including pressing on the side of the probe with InSight's robotic arm
to generate the required friction. This latter tactic has generated some
halting success, but the mole remains stranded too close to the
surface.
So,
in the next six to eight weeks, mission team members aim to try a
modification of the arm-pressing strategy, in which they'll push on the
mole's back rather than its side. The goal is to get the mole about 16
inches (40 centimeters) down, at which point it will hopefully be able
to start digging on its own, Banerdt said.
The
InSight team would also like a bit more cooperation from Mars on the
seismic side of things, if possible. The lander has not yet spotted any
truly big quakes, which have the potential to paint a clearer picture of
the planet's deep interior for mission scientists.
The lack of
powerful quakes is no surprise, Banerdt stressed; big tremors are much
rarer than their smaller counterparts here on Earth, after all. So, the
team may have to wait a while to get one.
https://www.space.com/nasa-insight-lander-mars-seismically-active.html?fbclid=IwAR2NNzs2dgXc-2K-sXS2vUnruDiMO9QmeA7zUHzs_JkMmekJu_eZjaHbIjA
