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Lander Offers New InSights on Martian Magnetic Field

mars magnetic field

Contributions to the Magnetic Field Measured by the InSight Fluxgate Magnetometer (IFG). Time varying fields are either of external origin (orange), including the interplanetary magnetic field, ionospheric currents and weather events such as dust devils; they can also be of lander origin (blue), e.g., due to movement of the arm, radio-science (RISE) communications, Solar Array Currents, or Martian temperature variations, measured by the temperature sensors on the lander. The Martian static crustal field (red) results from crustal magnetization, represented schematically here as subsurface dipoles. A steady field is also associated with the lander itself (green). Inset shows the IFG sensor box mounted under the lander deck. 

 

Investigations by NASA’s InSight lander have found that the Martian magnetic field is 10 times stronger than expected, while experiencing unexpected pulses, research by PSI’s Catherine Johnson says. 

“We know from previous work based on satellite data that about 4 billion years ago Mars had a global magnetic field that is no longer present,” Johnson said. This field magnetized ancient rocks that can still be found on the surface, though most are now between 200 feet (61 meters) to several miles below ground. InSight has found that the magnetic field at Homestead hollow is 10 times stronger than expected based on data from orbiting spacecraft. Those previous measurements were averaged over a couple of hundred kilometers; InSight's ground-level sensor — the first on Mars — provides a view of the local magnetic field. 

Because most rocks at the surface at InSight's location are too young to have been magnetized by the planet's former field, "this magnetism must be coming from ancient rocks underground," Johnson said. "We're combining these data with what we know from seismology and geology to understand the magnetized layers below InSight. How strong or deep would they have to be for us to detect this field?" 

The magnetic field also pulses mysteriously, typically around midnight on Mars. It's likely these pulses originate in space above Mars. Before InSight, scientists weren't sure whether weak signals from space could be detected at the Martian surface. In the future, the InSight team wants to observe the surface magnet field at the same time that NASA’s MAVEN orbiter passes over InSight, several hundred kilometers above the surface, allowing the team to compare data.

 

March 15, 2020
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