Enormous solar flares key to life on Earth
SOME 4 BILLION years ago, the Sun only shone with about 70 per cent of the brightness we see today, meaning Earth should have been an uninhabitable icy ball.
Instead, we know from geological evidence that Earth was in fact a warm globe with liquid water at the time; perfect conditions for life.
This is called the ‘Faint Young Sun Paradox’, and until now it has hindered our ability to fully map the Earth’s evolution.
Now, NASA scientists say they may have solved this paradox, in a study published in the journal Nature Geoscience this week.
Stormy adolescence and greenhouse gases
According to the new research, powerful solar explosions on the surface of the Sun 4 billion years ago may have provided the crucial energy needed to warm the Earth despite the Sun’s faintness. The enormous solar flares may also have provided the energy needed to turn simple molecules into complex molecules such as DNA and RNA.
The NASA scientists studied similar stars in our galaxy to piece together a functional timeline of how our own Sun evolved. They found that young stars frequently produce powerful solar flares and huge clouds of solar material called Coronial Mass Ejections (CME).
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While our Sun still produces flares and CMEs, they are not as frequent or intense as back then. Earth also has a stronger magnetic field today, which helps keep out the bulk of the energy from space weather. However, space weather does still occasionally impact Earth with so called ‘geomagnetic storms’ affecting radio communications and our satellites. This is also what causes aurorae, the northern and southern lights.
“Our calculations show that you would have regularly seen auroras all the way down in South Carolina,” said Vladimir Airapetian, lead author of the paper and a solar scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The make-up of early Earth’s atmosphere was also different to what it is now, with more powerful greenhouse gases contributing to the warming of early Earth.
“As the particles from the space weather travelled down the magnetic field lines, they would have slammed into abundant nitrogen molecules in the atmosphere. Changing the atmosphere’s chemistry turns out to have made all the difference for life on Earth,” Vladimir added.
The search for life on other planets
Understanding the conditions necessary for life on Earth can help not only trace the origins of life on our own planet, but also guide the search for life elsewhere in the universe.
“We want to gather all this information together, how close a planet is to the star, how energetic the star is, how strong the planet’s magnetosphere is in order to help search for habitable planets around stars near our own and throughout the galaxy,” said William Danchi, principal investigator of the project at Goddard and a co-author on the paper.
Source: NASA
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