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Sweet surprise: Look inside Mars reveals the Red Planet's crust resembles a three-layer cake


Sweet surprise: NASA Insight lander’s first look inside Mars reveals the Red Planet’s crust resembles a three-layer cake

  • The lander’s seismometer has recorded over 480 marsquakes since April 2019
  • Differences in how seismic waves move lets scientists evaluate the crust’s size and composition
  • They believe Mars’ crust is about 23 miles thick,  far thicker than the Earth’s
  • Seismic activity has virtually stopped, with only four quakes since June 

Data beamed back to Earth from NASA‘s InSight lander suggests Mars’ crust is composed of three cake-like layers.

Anchored near Mars’ equator, the robotic lander’s super-sensitive seismometer, known as SEIS, has recorded hundreds of ‘marsquakes’ in the past two years.

Each quake emits two sets of seismic waves and analyzing the differences in how those waves move has allowed researchers to begin calculating the size and composition of the planet’s crust, mantle and core. 

‘We have enough data to start answering some of these big questions,’ Jet Propulsion Laboratory scientist Bruce Banerdt told Nature

Launched in 2018, the InSight mission marks the first time scientists have peered inside a planet other than Earth.

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Analysis of primary and secondary waves caused by hundreds of marsquakes suggests the red planet's crust is composed of three 'cake-like' layers

Analysis of primary and secondary waves caused by hundreds of marsquakes suggests the red planet’s crust is composed of three ‘cake-like’ layers

The Earth’s crust is divided into three sublayers of rock: metamorphic, igneous and sedimentary.

Scientists had theorized Mars’ crust was similarly structured but, until now, had no data to work with. 

According to the report in Nature, it’s possible Mars only has two layers but a three-layer crust aligns with analysis of Martian meteorites. 

By comparing the marsquakes’ primary and secondary waves, they’ve deduced the crust is about 23 miles thick on average, and close to 42 at its thickest.  

NASA's InSight lander arrived on Mars in 2018, but its 'Mole' probe has had difficulty drilling beneath the surface

NASA’s InSight lander arrived on Mars in 2018, but its ‘Mole’ probe has had difficulty drilling beneath the surface

InSight's super-sensitive seismometer, known as SEIS, has recorded more than 480 marsquakes. Analyzing primary and secondary waves from these quakes, researchers believe Mars' crust is about 23 miles thick

InSight’s super-sensitive seismometer, known as SEIS, has recorded more than 480 marsquakes. Analyzing primary and secondary waves from these quakes, researchers believe Mars’ crust is about 23 miles thick

That’s considerably thicker than Earth, which has a crust that varies from about 3 miles under the oceans, up to 18 miles beneath the continents. 

InSight (short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) arrived on Mars in November 2018.

Its probe, dubbed the ‘Mole,’ was designed to dig beneath the surface and take the planet’s temperature — but unexpected properties in martian soil made progress difficult.

Other equipment on the lander is fully functional, thankfully—including the seismometer, provided by the French space agency, Centre National d’Études Spatiales.

Since April 2019, SEIS has recorded more than 480 quakes. The tremors are  relatively mild, with none larger than a magnitude 3.7.

‘It’s a little surprising we haven’t seen a bigger event,’ said seismologist Mark Panning of NASA’s Jet Propulsion Laboratory.

Panning says it’s not clear yet whether Mars is just more static than Earth or if InSight landed during a quiet interlude.

The quakes had been daily for some time, but abruptly stopped in late June—right around the time the planet entered its windiest season of the year.

The seismometer has shielding, but it’s possible the wind is so strong its shaking the ground and masking legitimate tremors.

Researchers hope more major quakes follow, giving greater insight into the planet’s inner layers.

‘Sometimes you get big flashes of amazing information, but most of the time you’re teasing out what nature has to tell you,’ Banerdt said.

‘It’s more like trying to follow a trail of tricky clues than having the answers presented to us in a nicely wrapped-up package.’

WHAT ARE INSIGHT’S THREE KEY INSTRUMENTS?

The lander that could reveal how Earth was formed: InSight lander set for Mars landing on november 26th

The lander that could reveal how Earth was formed: InSight lander set for Mars landing on november 26th

Three key instruments will allow the InSight lander to ‘take the pulse’ of the red planet:

Seismometer: The InSight lander carries a seismometer, SEIS, that listens to the pulse of Mars. 

The seismometer records the waves travelling through the interior structure of a planet. 

Studying seismic waves tells us what might be creating the waves. 

On Mars, scientists suspect that the culprits may be marsquakes, or meteorites striking the surface. 

Heat probe: InSight’s heat flow probe, HP3, burrows deeper than any other scoops, drills or probes on Mars before it. 

It will investigate how much heat is still flowing out of Mars. 

Radio antennas: Like Earth, Mars wobbles a little as it rotates around its axis. 

To study this, two radio antennas, part of the RISE instrument, track the location of the lander very precisely. 

This helps scientists test the planet’s reflexes and tells them how the deep interior structure affects the planet’s motion around the Sun.



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