Science
NASA-funded studies link Sun's ancient history to Earth's climate and early life
Computer simulations and experiments show how interstellar clouds and ancient solar superflares influenced Earth's historical climate.
The short version
- Two new studies examine how the Sun's interactions with interstellar clouds and solar superflares impacted Earth's ancient climate.
- Simulations show the heliosphere shrank past Earth's orbit at least three times, exposing the atmosphere to cold galactic hydrogen clouds that may have driven ancient ice ages.
- Laboratory tests demonstrate that superflares from a younger Sun could have produced nitrous oxide, helping solve the Faint Young Sun paradox by warming early Earth above freezing.
- Researchers plan to use these insights and digital modeling to further study the evolution of life and evaluate the habitability of other star systems.
Key facts
- Researchers at NASA's SHIELD center determined that the Sun encountered interstellar cold clouds approximately 2–3 million, 6–7 million, and 13–14 million years ago.[NASA News]
- The encounters compressed the heliosphere to a size smaller than Earth's orbit, exposing the planet to galactic hydrogen, cosmic radiation, and interstellar dust.[NASA News]
- Geologic evidence matching the simulation timelines for interstellar dust exposure includes deep-sea sediment cores, Antarctic snow, and lunar samples.[NASA News]
- A second study addressed the Faint Young Sun paradox, which questions how Earth maintained liquid water 3 billion years ago when the Sun was 70 percent as bright as today.[NASA News]
- Simulated atmospheric tests showed proton bombardment from solar superflares generated nitrous oxide, a greenhouse gas capable of warming Earth's equatorial regions to about 41 degrees Fahrenheit.[NASA News]
What remains uncertain
- The exact proportion of generated nitrous oxide that survived degradation by the young Sun's ultraviolet radiation remains uncertain, though models show a 10 percent survival rate would suffice to warm the planet.[NASA News]