"Earth and Moon Once Shared a Magnetic Shield, Protecting Their Atmospheres"

[krispos42]

Oct. 14, 2020

Earth and Moon Once Shared a Magnetic Shield, Protecting Their Atmospheres

Four-and-a-half billion years ago, Earth’s surface was a menacing, hot mess. Long before the emergence of life, temperatures were scorching, and the air was toxic. Plus, as a mere toddler, the Sun bombarded our planet with violent outbursts of radiation called flares and coronal mass ejections. Streams of charged particles called the solar wind threatened our atmosphere. Our planet was, in short, uninhabitable.

But a neighboring shield may have helped our planet retain its atmosphere and eventually go on to develop life and habitable conditions. That shield was the Moon, says a NASA-led study in the journal Science Advances.

“The Moon seems to have presented a substantial protective barrier against the solar wind for the Earth, which was critical to Earth’s ability to maintain its atmosphere during this time,” said Jim Green, NASA’s chief scientist and lead author of the new study. “We look forward to following up on these findings when NASA sends astronauts to the Moon through the Artemis program, which will return critical samples of the lunar South Pole.”



At certain times, the Moon’s magnetosphere would have served as a barrier to the harsh solar radiation raining down on the Earth-Moon system, scientists write. That’s because, according to the model, the magnetospheres of the Moon and Earth would have been magnetically connected in the polar regions of each object. Importantly for the evolution of Earth, the high-energy solar wind particles could not completely penetrate the coupled magnetic field and strip away the atmosphere.



Written by Elizabeth Landau
NASA Headquarters
Last Updated: Oct. 15, 2020
Editor: Tricia Talbert

https://www.nasa.gov/feature/earth-and-moon-once-shared-a-magnetic-shield-protecting-their-atmospheres

I think this is interesting because it seems to me to challenge the "principle of mediocrity" that we assume about our solar system. After all, we've only examined one solar system in detail: ours. We assume there is nothing special about our system... but maybe we're wrong.

We know, based on the history of our planet, that life needs liquid water and plenty of time to evolve to achieve complexity. Scientists believe life began some 3.75 billion years ago, but multi-cellular life took over two billion years to emerge.

Astronomers call the region around a star where a plant has liquid water and moderate temperatures the "Goldilocks" zone; not too hot, and not too cold. So in order for life to have the conditions and time to evolve, a planet has to not only be in the Goldilocks zone, but it has to stay there for billions of years! And the zone moves based on the star's output, so the planet has to be in a much smaller long-term zone that stays in the Goldilocks zone over billions of years.

Okay, so maybe that's not that uncommon in the universe. Planets form, stars form, and some planets are in the long-term Goldilocks zone. Some aren't, and maybe life started but then the planet got too cold and froze, or maybe some were too hot for a couple of billion years and by the time they got in the Goldilocks zone they were dry and barren. So maybe a quarter or a third or a tenth of planetary formations occur in the long-term Goldilocks zone. That's still tens of billions of stars in our galaxy alone. So, pretty common.

But now we need a really big moon. I mean, way bigger than we should. We need this moon to stabilize our axial tilt, so Earth's axis of rotation doesn't wander all over the place and do something fatal like point the north pole at the sun for a few hundred million years.

And, as the article discusses, it also provides extra protection from radiation and energetic particles during the early formation of life on Earth by having a linked magnetic field between the two.

And maybe we need big tides to force water-borne life to start to adapt to land by making tidal pools that have more extreme conditions than the quiet depths of the oceans.

Maybe THIS is what makes life on Earth unique and improbable. Maybe the odds of a rocky planet in the long-term Goldilocks zone having a really big and protective satellite is exceedingly rare.

The most popular theory of the Moon's creation has a Mars-sized body is a nearly-identical orbit to Earth's spiraling in for a (relatively) slow-motion collision that created a big and close satellite. The collision also deposited a chunk of the Mars-sized body's core into the Earth, giving us a larger-than-normal core and thus stronger-than-normal magnetic field. The rest of the Mars-sized body's core became the core of the Moon, and per the article, for a while the Moon was close to us and had a magnetic field that combined with ours.

Maybe THIS astronomical rarity is what makes conditions for long-term life rare as well. And since only a few solar systems have this combinations of events, it's possible that there are only a few thousand solar systems in the galaxy where conditions exist for life to grow and evolve for billions of uninterrupted years.

And if intelligent, tool-using, and communicating life is also rare... maybe we're alone in the Galaxy after all.

[AllaN01Bear]

1. if so, what a bunch of wasted space . ive always wanted to have breakfast with an alien.