Did our ancient sun go on a diet? Bands of martian rock could solve the ‘faint young sun’ paradox

[Elderberry]

Science By Joshua Sokol 12/3/2018

When Earth was a mass of newly minted rock some 4.5 billion years ago, the solar system was a cold place. Physicists predict our young sun put out some 15% to 25% less energy than it does today—enough to freeze over Earth’s oceans and make Mars even colder. Yet ancient rocks suggest water flowed across both planets, posing a perplexing puzzle.

For years, climate modelers solved this so-called “faint young sun” paradox by proposing that ancient atmospheres on both planets had the right composition of greenhouse gases to insulate them and keep them above freezing. But if the young sun reached its current weight only after a diet—shedding perhaps 5% of its early mass in a stellar wind of escaping particles—it would have burned brighter in its past than predicted, resolving the paradox. The only problem with that hypothesis? Scientists have had no way of knowing whether this stellar slim-down happened.

Now, astronomers say they have come up with a potential “fingerprint” of the sun’s ancient mass—climate cycles preserved in bands of martian rocks. To find their marker, Christopher Spalding, a planetary astronomer at Yale University, geobiologist Woodward Fischer at the California Institute of Technology in Pasadena, and astronomer Gregory Laughlin of Yale started with an orbital cycle that both Earth and Mars experience. As the solar system’s planets revolve around the sun, their own gravity tweaks each other’s orbits.

More: https://www.sciencemag.org/news/2018/12/did-our-ancient-sun-go-diet-bands-martian-rock-could-solve-faint-young-sun-paradox

[Elderberry]

Gravity of Venus and Jupiter Elongates Earth’s Orbit Every 405,000 Years

http://www.sci-news.com/featurednews/venus-jupiter-earths-orbit-climate-05983.html

A research team led by Rutgers University’s Professor Dennis Kent has documented a gradual shift in Earth’s orbit that repeats regularly every 405,000 years, playing a role in natural climate swings. Astrophysicists have long hypothesized that the cycle exists, but Professor Kent and co-authors have found the first verifiable physical evidence; they showed that the cycle has been stable for at least 215 million years and is still active today.

Researchers have for decades posited that Earth’s orbit around the Sun goes from nearly circular to about 5% elliptical, and back again every 405,000 years.

The shift is believed to result from a complex interplay with the gravitational influences of Venus and Jupiter, along with other bodies in the Solar System as they all whirl around the Sun like a set of gyrating hula-hoops, sometimes closer to one another, sometimes further.

Astrophysicists believe the mathematical calculation of the cycle is reliable back to around 50 million years, but after that, the problem gets too complex, because too many shifting motions are at play.

“It’s an astonishing result because this long cycle, which had been predicted from planetary motions through about 50 million years ago, has been confirmed through at least 215 million years ago,” Professor Kent said.

“Scientists can now link changes in the climate, environment, dinosaurs, mammals and fossils around the world to this 405,000-year cycle in a very precise way.”

The researchers linked reversals in the Earth’s magnetic field to sediments with and without zircons as well as to climate cycles.

“The climate cycles are directly related to how the Earth orbits the Sun and slight variations in sunlight reaching Earth lead to climate and ecological changes. The Earth’s orbit changes from close to perfectly circular to about 5% elongated especially every 405,000 years,” Professor Kent said.

More at link above.

[Elderberry]

Rock-solid evidence shows how Earth's eccentric orbit affects climate change

"It's an astonishing result because this long cycle, which had been predicted from planetary motions through about 50 million years ago, has been confirmed through at least 215 million years ago," says Kent. "Scientists can now link changes in the climate, environment, dinosaurs, mammals and fossils around the world to this 405,000-year cycle in a very precise way."

https://newatlas.com/earth-orbit-climate-change/54539/