Even though Mars has lost much of its overall magnetic field, some areas still create unique atmospheric electrodynamic structures – magnetic loops and cusps which alter how ions leave its atmosphere.
Sabine Stanley and her colleagues have developed an effective technique for artificially creating these structures. Their paper published in Science details how this can be accomplished.
Earth’s Magnetic Field
Earth’s magnetic field acts as a shield, deflecting charged particles found in solar wind away from our planet while trapping them within an expanding doughnut-shaped region called Van Allen radiation belts. As a result, an enormous magnetosphere encircles our dayside globe and extends out as an outgoing tail at nighttime to protect us from most of the sun’s powerful radiation.
The Earth’s magnetic field is complex and not fully understood. Although dipole in form, its behavior owes much more to non-dipole components which add an additional dimension of complexity than can be discerned simply from looking at a linear representation of its vector field vectors. Compasses will not point directly at magnetic poles because these other influences distort this straight-line drawing of its vector field.
Earth’s core serves as an immense dynamo that drives its magnetic field, where liquid metals like iron and nickel churn with each rotation on its axis, producing electrical currents which then generate the magnetic field. Once generated, its effects can be “frozen” into rocks through magnetostratigraphy by recording their direction using samples cooled down over time with radiometric dating technology; such records provide an archive for reconstructing Earth’s history in terms of magnetic field patterns.
Over geological timescales, Earth’s magnetic field has the ability to shift, with its north and south magnetic poles swapping places. These changes, known as geomagnetic reversals (GMRs), often include changes in rotation rate and tilt of its axis as well as unpredictable effects that could disrupt communications, navigation, or any number of human activities.
GMR occurs when magnetic field lines depart Earth’s geographic poles and curve away, similar to what can be observed with stars and some planets’ rotation and magnetic fields. This phenomenon helps us better understand plate tectonic movement as well as navigation and communications industries who use satellites to detect field variations and make adjustments accordingly for their systems.
The Sun’s Magnetic Field
The Sun boasts an enormous magnetic field that dwarfs that of Earth. This magnetic field is produced by churning of charged particles within its core, and extends outward into space. This magnetic field redirects and shields solar radiation from reaching Earth surface while helping reduce atmospheric molecules stripped away by solar wind during large solar events.
The Sun’s magnetic fields can be observed in its outer atmosphere, known as the corona. EUV images make this phenomenon apparent. At solar minimum, open magnetic field lines (in yellow) become tangled together into sunspots while closed field lines (traced in teal) loop back onto themselves to trap plasma into planet-sized arches called coronal loops which help guide solar material away into interplanetary space at approximately 750 km/s speed.
Researchers believed that Mars had lost its global magnetic field 4 billion years ago, which would have prevented it from maintaining an atmosphere and protecting itself against solar wind. But according to a new study published by Science, its loss wasn’t as dramatic.
Scientists now suspect that this loss was the result of changes in core temperature. When this happened, convection of immiscible hydrogen and sulphur-rich liquids that create Earth’s magnetic field ceased, leading to its breakdown and eventual disappearance from Mars’ iron core – thus rendering its loss impossible to explain using similar mechanisms as with Earth.
This new research allows scientists to use data from Mars’ satellites to generate a model of its magnetic field. This allows for improved interpretations of observations of Mars surface observations for signs of dynamo cessation timing or ancient magnetic field directions, or interactions between its surface and solar wind. Furthermore, understanding processes that create and destroy its magnetosphere could help create more conducive conditions for human mission terraforming activities or protect future missions to this distant world.
The Moon’s Magnetic Field
Researchers studying the Moon have made an exciting discovery: its magnetic field has existed much longer than previously believed. Magnetic fields serve an essential purpose: they protect planets and their moons against solar wind particles and ionizing radiation that threaten their existence. These new findings could have important ramifications for the search for habitability on other planetary bodies, as published today in Science Advances by Sonia Tikoo, an assistant professor from Rutgers University-New Brunswick’s Department of Earth and Planetary Sciences. “Our findings demonstrate that the Moon’s magnetic field lasted 1 billion to 2.5 billion years longer than we initially believed,” Tikoo noted. This finding could be explained by iron-rich mantle lithosphere in its interior which can sustain such magnetic fields.
The Moon does not feature a global magnetic field emanating from its core like our own planet does, instead its surface exhibits many locally concentrated magnetic anomalies which tend to form around large impact basins and volcanic provinces. According to MGS data models, these anomalies appear associated with magnetization within its underlying lithosphere.
Magnetization acquisition explains these local magnetic anomalies rather than core dynamo magnetic fields, with electric currents flowing reversibly from lithosphere to plasma due to impact heating, leading to an asymmetry that allows lithosphere locking resulting in the creation of magnetic fields.
MGS data also demonstrate that the Moon’s magnetic anomalies are non-bipolar; in other words, they don’t have a clear north and south pole. This evidence supports the hypothesis that their production involves current exchange in an ocean-locked lithosphere. Future observations, including InSight surface magnetic measurements from MGS mission, should help resolve discrepancies while also offering insight into processes responsible for electric current exchange and subsequent magnetization processes.
Mars’ Magnetic Field
Scientists are providing stunning visualisations of Mars’ magnetic data, unveiling previously hidden flows of energy. After analysing five years’ worth of MAVEN mission data from NASA and creating maps that depict electrical currents forming double loop structures around Mars – currents thought to be responsible for atmospheric stripping that has reduced Mars to an inhospitable desert world.
Researchers believe a magnetic field could be one of the key steps towards terraforming Mars. A strong magnetic field would help slow down atmospheric loss while shielding against harmful radiation particles from the sun that are currently stripping it of atmosphere. Researchers at RAL (Rutherford Appleton Laboratory) Space in Oxfordshire, England have long studied this idea and provide technological solutions that enable an artificial magnetosphere around our planet.
Modells by these researchers demonstrate that once upon a time, a core-dynamo process powered the magnetic field on Mars; however, its strength gradually declined until eventually dissipating altogether approximately 4.2 billion years ago allowing solar winds to strip it bare of any atmosphere that might have made life possible.
Recent analyses of rocks near Mars Polar Crater Noachis Terra have uncovered magnetic anomalies which suggest the existence of an active magnetic field that may have been altered by this dynamo, yet further surface measurements will likely be necessary to reach definitive results.
Because Mars lacks a solid metal core, scientists believe its residual magnetic field originates from old rock layers buried several hundred feet below its surface and has remained there for billions of years. To gain further understanding into how and where this magnetic field emanates from, future missions are planned that will measure its strength at Mars’ surface as well as observe any changes over time.