Temporary dip in Earth’s magnetic field may have helped complex life emerge. Really!

This period of a weakened magnetosphere lasted only 26 million years! Does this geologically short blip matter so much?

"Complex life on Earth may have emerged more than 541 million years ago due to strange fluctuations in the planet’s unique magnetic field.

Unlike its 3 closest rocky planets, Earth produces a magnetosphere thanks to convective interactions in the planet’s iron core layers. This generates huge electrical currents that extend beyond the crust and form a ‘shield’ to protect against harmful solar radiation from the Sun. ...

Records show that soft-bodied animals underwent a surge in diversification 575-565 million years ago and likely due to increased oxygen in the atmosphere and ocean.

A dip in the strength of Earth’s magnetic field 591-565 million years ago happened alongside the oxygen spike. ...
The analysis indicates the massively weakened magnetic field persisted for around 26 million years. Tarduno’s team suggests the rise in the percentage of oxygen may have been caused by the escape of atmospheric hydrogen through the Earth’s weakened shield. ..."

"Researchers ... have uncovered compelling evidence that Earth’s magnetic field was in a highly unusual state when the macroscopic animals of the Ediacaran Period diversified and thrived. Their study ... raises the question of whether these fluctuations in Earth’s ancient magnetic field led to shifts in oxygen levels that may have been crucial to the proliferation of life forms millions of years ago. ...

Leveraging cutting-edge tools, including a CO2 laser and the lab’s superconducting quantum interference device (SQUID) magnetometer, the team analyzed with precision the crystals and the magnetism locked within. ...

A weak magnetic field makes it easier for charged particles from the sun to strip away lightweight atoms such as hydrogen from the atmosphere, causing them to escape into space. If hydrogen loss is significant, more oxygen may remain in the atmosphere instead of reacting with hydrogen to form water vapor. These reactions can lead to a buildup of oxygen over time. ..."

From the abstract:

"Earth’s magnetic field was in a highly unusual state when macroscopic animals of the Ediacara Fauna diversified and thrived. Any connection between these events is tantalizing but unclear. Here, we present single crystal paleointensity data from 2054 and 591 Ma pyroxenites and gabbros that define a dramatic intensity decline, from a strong Proterozoic field like that of today, to an Ediacaran value 30 times weaker. The latter is the weakest time-averaged value known to date and together with other robust paleointensity estimates indicate that Ediacaran ultra-low field strengths lasted for at least 26 million years. This interval of ultra-weak magnetic fields overlaps temporally with atmospheric and oceanic oxygenation inferred from numerous geochemical proxies. This concurrence raises the question of whether enhanced H ion loss in a reduced magnetic field contributed to the oxygenation, ultimately allowing diversification of macroscopic and mobile animals of the Ediacara Fauna."

Temporary dip in Earth’s magnetic field may have helped complex life emerge

Did a magnetic field collapse trigger the emergence of animals? (original news release) Evidence suggests a weak magnetic field millions of years ago may have fueled the proliferation of life.

Near-collapse of the geomagnetic field may have contributed to atmospheric oxygenation and animal radiation in the Ediacaran Period (open access)

Fig. 3: Paleointensity, oxygen and animal evolution.