Approximately every millennium, Earth is struck by a devastating event of extreme solar particles. These proton storms, originating directly from the Sun, can penetrate our atmosphere and cause significant damage to the environment and life on Earth. Scientists are now questioning the consequences of these phenomena, especially during periods of weak magnetic fields.
Earth's magnetic field, our shield against solar radiation, undergoes significant fluctuations over time. Over the past century, the magnetic north pole has moved 25 miles (40 kilometers) per year, and the field has lost more than 6% of its intensity. Periods of weak magnetic field have been recorded in geological history, and the complete absence of this field has dramatic consequences, as evidenced by Mars.
Solar particle events are characterized by the massive emission of protons from the Sun, often associated with solar flares. Unlike electrons, protons, which are heavier and more energetic, can reach lower altitudes in Earth's atmosphere, generating X-rays that are invisible to the naked eye. Such events occur regularly, but some in Earth's history have been thousands of times more powerful than those observed with our current instruments.
The consequences of an extreme solar particle event on Earth's ozone and UV radiation levels are alarming. During these events, a series of chemical reactions can significantly deplete the ozone layer, thereby increasing UV exposure, which raises the risks of skin cancer and affects the climate. If these events occur when the magnetic field is weak, the damage can last for years, increasing UV levels by 25% and DNA damage by 50%.
The study of periods of weak magnetic fields and extreme solar events reveals correlations with mass extinctions and significant evolutions in life on Earth. For example, the extinction of the Neanderthals and marsupial megafauna coincides with a period of weak magnetic field 42,000 years ago. Similarly, the appearance of the first multicellular animals and the Cambrian explosion could be linked to these geomagnetic variations and elevated UV radiation levels.
Scientists continue to seek to understand the influence of solar activity and Earth's magnetic field on the evolution of life, exploring new avenues to explain the great transitions in biological history.