When scientists are asked what led to the first appearance of life on Earth almost four billion years ago, many point to the planet's rocky surface, the presence of water and its unique atmosphere. Now, a new study reveals a lesser-known factor that played an important role in its evolution: its magnetic field.
"To be habitable, a planet needs warmth, water, and it needs to be sheltered from a young, violent Sun," said Jose-Dias Do Nascimento, lead author of the study.
Nascimento and his team made the discovery by examining Kappa Ceiti, a young star that is much like our sun. The age of the star - around 400 to 600 million years old - corresponds to the approximate time that life first appeared on Earth, allowing the team to use insights from its examination to better grasp the early history of our solar system.
Kappa Ceti is very magnetically active, a trend that is common in most stars its age. Its surface possesses many giant starspots, which resemble sunspots, and it propels a steady stream of ionized gases into space that is 50 times stronger than the sun's solar wind.
These strong stellar winds are enough to damage the atmosphere of any planet that is habitable unless its is protected by a magnetic field. Without an adequate magnetic field, planets could lose their atmosphere due to such factors, something that we know happened to Mars and ultimately turned it into a cold, dry desert planet.
Using computer models, the team created a depiction of the stellar wind of Kappa Ceti and its effects on a young Earth, which is believed to have possessed a magnetic field roughly the same strength as it is today, if not slightly weaker. The results showed that Earth's early magnetosphere protected it.
"The early Earth didn't have as much protection as it does now, but it had enough," Do Nascimento said.
The team also believes that Kappa Ceti may produce "superflares," which are large eruptions that create 10 to 100 million times more energy than the biggest flares we have ever seen on the sun. Such flares could destroy a planet's atmosphere, giving the researchers hope that exploring these phenomena will help them better understand how the sun erupted years ago and its effects on a young Earth.
The findings were published March 12 on pre-print server arXiv.
