Solar storms four billion years ago may have provided the crucial energy needed to warm Earth and seed life despite the Sun’s faintness, new research has revealed.
Some four billion years ago, the sun shone with only about three-quarters the brightness we see today, but its surface roiled with giant eruptions spewing enormous amounts of solar material and radiation out into space.
The eruptions also may have furnished the energy needed to turn simple molecules into the complex molecules such as RNA and DNA that were necessary for life, said NASA researchers.
“Back then, Earth received only about 70 percent of the energy from the Sun than it does today,” said Vladimir Airapetian, solar scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
That means Earth should have been an icy ball.
“Instead, geological evidence says it was a warm globe with liquid water. We call this the ‘Faint Young Sun Paradox’. Our new research shows that solar storms could have been central to warming Earth,” he added.
Understanding what conditions were necessary for life on our planet helps us both trace the origins of life on Earth and guide the search for life on other planets.
Until now, however, fully mapping Earth’s evolution has been hindered by the simple fact that the young Sun wasn’t luminous enough to warm Earth.
Scientists are able to piece together the history of the sun by searching for similar stars in our galaxy.
By placing these sun-like stars in order according to their age, the stars appear as a functional timeline of how our own Sun evolved.
It is from this kind of data that scientists know the sun was fainter four billion years ago.
Such studies also show that young stars frequently produce powerful flares - giant bursts of light and radiation -- similar to the flares we see on our own Sun today.
Such flares are often accompanied by huge clouds of solar material, called coronal mass ejections or CMEs which erupt out into space.
NASA’s Kepler mission has found stars that resemble our sun about a few million years after its birth.
The Kepler data showed many examples of what are called “superflares” - enormous explosions so rare today that we only experience them once every 100 years or so.
Yet the Kepler data also show these youngsters producing as many as 10 superflares a day.
While our sun still produces flares and CMEs, they are not so frequent or intense.
What’s more, Earth today has a strong magnetic field that helps keep the bulk of the energy from such space weather from reaching Earth, the authors said.
Our young Earth, however, had a weaker magnetic field, with a much wider footprint near the poles.
This newly discovered constant influx of solar particles to early Earth may have done more than just warm the atmosphere; it may also have provided the energy needed to make complex chemicals.
In a planet scattered evenly with simple molecules, it takes a huge amount of incoming energy to create the complex molecules such as RNA and DNA that eventually seeded life.
While enough energy appears to be hugely important for a growing planet, too much would also be an issue -- a constant chain of solar eruptions producing showers of particle radiation can be quite detrimental.
Such an onslaught of magnetic clouds can rip off a planet’s atmosphere if the magnetosphere is too weak.
Understanding these kinds of balances help scientists determine what kinds of stars and what kinds of planets could be hospitable for life.
The research was published in the journal Nature Geoscience.