Science & Technology - Posted by Brian Peloza-Purdue on Thursday, May 31, 2012 11:29 - 8 Comments 
(No Ratings Yet)
Loading ...
(No Ratings Yet) Loading ...Did orbit mishap save Earth from freezing?
"I calculated to keep the Earth from being frozen over at the beginning of its history, it would have to be 6 or 7 percent closer to the sun than it is now," says Purdue University's David Minton. "It's a few million miles, but from an orbital mechanics standpoint, it's not that far. The question is what could make a planet move from one location to another?" (Credit: "Sun rising above planet" via Shutterstock)
PURDUE (US) — More than 2 billion years ago, a much fainter sun should have left the Earth as an orbiting ice ball, unfit to develop life as we know it today.
Share this article
Email
Republish this article
The text of this article by Futurity is licensed under a Creative Commons Attribution-No Derivatives License.
Why the Earth avoided the deep freeze is a question that has puzzled scientists, but David Minton believes he might have an answer.
“If you go back in time to about 2 billion years ago, the earth should have been frozen over,” says Minton, an assistant professor of earth, atmospheric and planetary sciences at Purdue University. “There’s a lot of geological evidence that the Earth wasn’t frozen over. So, what is not equal? That is the Faint Young Sun Paradox.”
Minton has offered a hypothesis of why the Earth avoided freezing over during a period when, according to geological and astrophysical observations, the sun burned at about only 70 percent of its current brightness. In short, he believes our planet might have been in a warmer place.
“I calculated to keep the Earth from being frozen over at the beginning of its history, it would have to be 6 or 7 percent closer to the sun than it is now,” Minton says. “It’s a few million miles, but from an orbital mechanics standpoint, it’s not that far. The question is what could make a planet move from one location to another?”
Ejected from orbit
Minton proposes the Earth may have migrated from the sun over time through a process called planet-planet scattering, which occurs when one planet or more is ejected from its orbit, an increase in orbital separation occurs, or when planets collide. He presented his hypothesis recently at the Space Telescope Science Institute in Baltimore.
Straight from the Source
There are many possible ways a planet could move, but Minton says most alternatives could be ruled out because of the timeline involved.
“You have a huge time scale range from 1 billion to 10,000 years ago to work with,” Minton explains. “While most theories can be ruled out, planet-planet scattering is not ruled out. When a planet system or solar system forms there is no knowledge of how long they will be stable.
“They form and then they can go unstable in some time scale, and that time scale is set arbitrarily. Most of the instabilities happen early, and the longer you go in history, the more rare instabilities become. But rare does not mean never, and rare events can happen.”
Venus twins
Minton speculates two proto-Venus planets existed at one point and went into a chaotic and unstable phase, crossing the Earth’s path and boosting us to our familiar orbit.
The two proto-Venus planets then collided, forming the planet Venus that exists today.
“One way we could have ruled this out would be if Venus had a geological history older than 2 billion years ago. We know, though, Venus is a relatively young planet.”
The oldest surface on Venus is estimated to be 500 million to 700 million years old, a relatively young surface by planetary science standards. Impact craters on Earth can stretch back 1 billion to 2 billion years old, with a variety of ages on the surface.
“Venus looks like it became one age all at once,” Minton says. “Venus could look like it does because at some point in the last billion years it was two planets that collided and had this catastrophic event. This hypothesis of the Faint Young Sun Paradox fits the evolution of Venus.”
Minton will continue to research his hypothesis, which, if proven, could have several ramifications.
“It could say something about the evolution of life on Earth,” Minton says. “Depending on when it happened, it could have had a major effect on the Earth’s biosphere. You’re basically shifting the Earth’s orbit from one area to another pretty dramatically.”
Minton notes that researchers from numerous disciplines have worked to solve the Faint Young Sun Paradox, including those from solar physics, astrophysics, geology, climatology, and planetary sciences.
“It’s one of the most all-inclusive subject areas in earth science because trying to understand it requires communicating with all of these different fields,” he adds.
More news from Purdue University: www.purdue.edu/newsroom
Please wait
8 Comments
Dunemi
Burton Richter
A stronger greenhouse effect than today’s can also account for the effect. Teo billion years ago atmospheric oxygen was only about a percent and CO-2 could have been much larger. We have lots of evidence that the greenohouse has varied over time.
Kimberley
Dunemi – nice thinking… but!
The sun has varied in its activity over time, yes. But when it comes to the positions of the orbits of the planets this is largely irrelevant.
What matters in the matter (pardon the pun!) by that I mean the mass (how much matter there is) of the star (sun) and the mass of the planets. The sun is massive (about 2,000,000,000,000,000,000,000,000,000,000 kg) by far the biggest object around for light-years. It is this huge mass that keeps everything orbiting a star.
The force that holds the bodies of the solar system in orbit is an attractive force – gravity. I really could go on about gravity all day it is so much more than what keeps us on the ground. But the important thing to note in this case is that all matter is attracted to other matter by the force of gravity, and that as the mass of the two bodies increases the greater that force is.
As stars are so massive they attract matter from millions of miles around and whole solar systems build up around them. The solar bodies are only going around the sun because they’re too far away to reach it despite the fact that they are constantly falling towards it. This falling results in an elliptical orbit. There have been lots of other objects, particularly when the sun was younger that were too close and did fall into the Sun and they helped contribute to its mass.
Some stars can have so much gravitational ‘power’ that they attract whole galaxies – black holes.
I hope you don’t think I’m being patronising, I’m sure you know much of this already. The point I’m trying to make is that the Sun and the Earth are attracted to each other by a very strong force that negates any push force that may result from solar winds etc. It would take something that would disrupt the gravitational balance within the solar system, such as the annihilation of planet as the article suggests, to change the position of a planets orbit. Planets are not only attracted to the Sun by gravity but to each other and to their own satellites.
It’s a bit like if you were to arrange marbles on a tightly stretched piece of nylon with the heaviest marble in the middle, the marbles would have to be carefully positioned – not too closely to each other or else they will try to occupy the same space. Changing the position or removing a marble would mean that the other marbles would shift their positions to regain the balance.
Hope that answers your question!
KenL
let’s see a calculation of the 30% increase of brightness on the orbit. It shouldn’t be difficult, and I’m sure it isn’t 0.000m.
Kimberley
Maybe you’d like to elaborate further? I’m not claiming to be an expert, I’m a biochemist with an interest in cosmology. If you know more on the topic I’d also be interested to hear it.
Dunemi
@Kimberly,
Thanks for the explanation.
Kimberley
No problem :) although it sounds like KenL knows more, so your theory may be right after all!
Tim
I am curious why the mechanism that has caused the moon to steadily move further and further out, can not be the same mechanism that has caused the earth to steadily move further and further out.
Basically as I understand it, when one object orbits and other the ultimate stable state is for the object to be tidally locked with the other object. Basically they always show one another the same face. (Don’t ask me the why that do that, I just know that objects like to become tidally locked over time) Over time the object that is moving faster will “pull” on the object that moving slower. In the case of the Earth and Moon, the Earth is moving much faster around that the Moon. Over time the Earth has slowed down and this energy has mostly been lost to speeding up the Moon. As the moon speeds up, this boosts it a higher and higher orbit.
Last time the checked the Sun orbits around its axis much faster than we orbit around it. This process would be a LOT more smooth and gentle than a one time boost by proto Venus twin being ejected from the solor system.
I’m not a physicist, so can someone explain to me why the following conjecture is wrong/insane/stupid? So my idea is, all the planets used to be closer to the sun, but as the sun became more active/energetic over time, the planets were “pushed” away by the force of this increased energy?