NASA’s InSight lander has discovered something totally unexpected and unique on the surface of Mars.
The red planet once possessed a global magnetic field of which traces remain evident in the rocks that make up its crust. Already in 1997 the probe Mars Global Surveyor was able to map the magnetic field of the Martian crust flying over the surface at an altitude ranging between 100 km and 400 km, detecting a magnetic intensity ten times higher than that of the Earth at the same altitude.
It is also known that the interaction between the solar wind and the atmosphere of Mars produces a magnetosphere with an elongated shape towards the shadow side of the planet.
Also the probe MAVEN has provided valuable information on the complex structure of the weak Martian magnetic field, but always measurements made from orbit.
The lander InSight instead is the first probe (and so far the only one) to provide us with measurements taken from the ground, measurements that have been found to be truly amazing!
The magnetometer of InSight has begun to amaze us by detecting a magnetic field twenty times more intense than expected based on the measurements made by the various orbiters that had already measured a magnetic intensity ten times higher than the Earth at the same altitude!
According to Dave Brain, physicist at the University of Colorado, if this high value was created by rocks near the surface we should admit that Mars has retained an intense global magnetic field for a much longer time than we thought until now.
But the most shocking surprise was to detect pulsations in the intensity and/or direction of the magnetic field with a frequency between 0.01 Hz and 1 Hz mainly during the night.
Similar pulsations on Earth are observed only at high latitudes and mainly during the auroras and never at the equator, as in the case of InSight. This singular behavior of the Martian magnetic field “could” be caused by the transit of the equatorial zones in the magnetic tail of the planet that would act on the local magnetic field in a similar way to the strings of a guitar when they are plucked, although at the moment it is a simple hypothesis and not a scientifically established fact.
Last but not least, from the data obtained from the magnetometer of InSight would emerge the presence of an electrically conductive layer under the surface at a depth less than 100 km.
This layer should be made of water mixed with salts or water mixed with ice that apparently would wrap the entire planet.
Obviously the presence of this global liquid water layer will require further verification that will be performed by future missions able to probe more or less directly the Martian subsurface.
The fact remains that the current image of Mars painted as a totally arid planet with no magnetic field is destined to be revolutionized in the very near future.
Sources:
National Geographic article by Robin George Andrews:
“Mysterious magnetic pulses discovered on Mars”. https://www.nationalgeographic.com/science/2019/09/mars-insight-feels-mysterious-magnetic-pulsations-at-midnight/
Free downloadable PDF publication:
“InSight Observations of Magnetic Pulsations on Martian Surface: Initial Findings and Implications”. https://meetingorganizer.copernicus.org/EPSC-DPS2019/EPSC-DPS2019-838-1.pdf
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