Earth is exclusive within the photo voltaic system for quite a few causes: It is the one planet with a breathable oxygen ambiance, it is coated in liquid water and it is the one celestial physique (that we all know of) to harbor life. An often-overlooked attribute that makes our planet particular, nevertheless, is that it is the solely rocky physique within the internal photo voltaic system with robust magnetic poles — your compass could be ineffective on Mars.
However the place do these poles come from, and what do they do? To reply these questions, let’s begin with a journey to the middle of our planet.
Earth’s core is separated into two layers: the strong internal core and the molten steel outer core. Each layers are product of a cocktail of magnetic iron and nickel, with a number of dashes of lighter components, corresponding to oxygen, silicon and sulfur.
The internal core is extraordinarily dense and scorching, like a large incandescent marble. However the outer core is fluid, and it swirls round this strong mass with its personal convective present. It is this fixed convection that generates Earth’s magnetic area, John Tarduno, a geophysicist on the College of Rochester in New York, instructed Dwell Science.
Associated: What if Earth’s magnetic area disappeared?
As warmth from the internal core repeatedly radiates into the outer core, it meets materials cooled by plate tectonic exercise. This cycle drives convection, giving rise to the so-called geodynamo that produces the magnetic area.
Different planets, like Mars and Venus, haven’t got magnetic fields, partially as a result of they lack plate tectonics. Proof means that these planets could have as soon as had self-sustaining geodynamos however that they petered out for unknown causes. Mercury does have a weak magnetic area, however it’s just one.1% as robust as Earth’s and does not do a lot to defend the planet from photo voltaic radiation.
Because the liquid steel in Earth’s outer core flows, its movement and excessive iron content material trigger the planet to behave like an enormous dipolar magnet, with one negatively charged pole and one positively charged pole. Round 80% of Earth’s magnetic area is organized this fashion, however the remaining 20% is non-dipolar; somewhat than forming parallel bands of magnetic pressure, there are specific areas the place the sector swirls and eddies, behaving “like climate patterns that form of float round,” Tarduno stated.
These irregular patterns produce bizarre patches within the magnetic area — locations just like the South Atlantic Anomaly, a big swath of the Atlantic Ocean the place the depth of Earth’s magnetosphere dips dramatically. Researchers assume this “dent” within the magnetic area arises from uncommon tectonic exercise beneath Africa. Areas just like the South Atlantic Anomaly are fascinating, however they’re additionally regarding, for a few causes.
“The magnetosphere is sort of a protecting envelope,” Joshua Feinberg, a geologist who makes a speciality of paleomagnetism on the College of Minnesota, instructed Dwell Science. It helps to deflect big quantities of harmful photo voltaic radiation away from Earth, performing like a planetwide layer of sunscreen. In areas the place the magnetosphere is weak, additional doses of radiation leak by, probably contributing to increased charges of pores and skin most cancers.
“One other concern is the impact on satellites,” Tarduno stated. Bursts of radiation from the solar referred to as coronal mass ejections can knock out satellites and different spacecraft if they don’t seem to be shielded by Earth’s magnetic area. This may have catastrophic results for telecommunications, web entry and GPS companies in anomaly-impacted areas.
The South Atlantic Anomaly could also be 11 million years previous, in keeping with a 2020 paper revealed within the journal PNAS, and it is likely to be related to a different planetary magnetic-field phenomenon: pole reversal.
The historical past of Earth’s magnetic area is written in historic lava flows and deep-sea sediments. A lot of these rocky materials are wealthy in magnetic steel fragments, corresponding to tiny chips of iron, which orient themselves alongside magnetic-field strains. “Finally, that authentic alignment will get locked into the sediments, and we get these deep-time data of how the Earth’s magnetic area was oriented,” Feinberg stated.
From these data, scientists know that our planet’s magnetic poles drift over time. Presently, the geographic North Pole is about 310 miles (500 kilometers) away from its corresponding magnetic pole (which is technically magnetic south, for the time being). And roughly each 300,000 years, the poles all of the sudden flip, reversing magnetic north and south, in keeping with NASA.
Nevertheless, the paleogeomagnetic report exhibits {that a} full pole reversal hasn’t occurred in about 780,000 years. Some researchers consider which means we’re due for a flip — and that the power of the South Atlantic Anomaly might point out that one is shut.
If the poles have been to reverse, Earth’s magnetic area would dip to twenty% power, presumably for hundreds of years. Such an occasion would plunge our present international communications system into disarray. Nevertheless, different research counsel that a flip isn’t imminent.
Both manner, Feinberg stated, learning our planet’s inside and the paleogeomagnetic report will assist us perceive the complicated interaction between the magnetosphere and life on Earth — and presumably assist us put together for future change.