Space

Massive star may be the reason Earth isn't a waterworld

Massive star may be the reason...
Artist’s rendering of researchers’ simulations showing how planetary systems born in dense and massive star formation regions (left) inherit substantial amounts of radioactive materials, making them much drier than those formed in different environments (right)
Artist’s rendering of researchers’ simulations showing how planetary systems born in dense and massive star formation regions (left) inherit substantial amounts of radioactive materials, making them much drier than those formed in different environments (right)
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Artist’s rendering of researchers’ simulations showing how planetary systems born in dense and massive star formation regions (left) inherit substantial amounts of radioactive materials, making them much drier than those formed in different environments (right)
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Artist’s rendering of researchers’ simulations showing how planetary systems born in dense and massive star formation regions (left) inherit substantial amounts of radioactive materials, making them much drier than those formed in different environments (right)

The Earth as a habitable planet may be rarer than we thought. Scientists have used computer models to show that the reason our planet and has a moderate climate and isn't an ocean world is because there was a massive star in the vicinity of the primordial solar system. This star provided the growing inner planets with radioactive elements that evaporated some of the water that otherwise would have been delivered to them.

One of the great scientific mysteries during the Victorian era was why the Earth wasn't a frozen wilderness? As geologist learned more about how to calculate the age of the planet accurately, the numbers produced a real poser because they found that the Earth shouldn't be anywhere near as warm as it is.

The accepted theory at that time was that the Earth had started out as a giant molten mass that gradually cooled off. This was the reason why the age of the dinosaurs was hotter than it is today and suggested that the planet would be cooler centuries from now. The problem was that geologists had discovered that the Earth was billions of years old, which meant that the world should have long ago been reduced to its ambient base temperature with the only heat coming from the Sun to warm it.

However, that wasn't the case. The Earth is very warm and the interior is molten and very active. Why? The answer came with the discovery of radioactivity. It was found that the presence of radioactive elements like uranium provide the interior of the Earth with an energy source that keeps it hot even after many epochs of cooling.

Today, scientists have learned much more about how planets form and one result of the latest computer simulations is that a planet like the Earth is very odd. We think of it as being watery – comparing it to planets like Mercury or Mars, the oceans that cover 75 percent of the Earth's surface do make it seem like a water world. But the models say that in a planetary system like ours, the Earth should be a giant ball of ice with a frozen ocean many miles thick covering the entire surface from pole to pole.

According to University of Michigan astronomer Michael Meyer, the computer simulations provided part of the answer if it's assumed that there was a massive star in the area of the solar system as it formed. When such stars reach the end of their lives, they go nova and expel enormous amounts of matter with some of it made up of radioactive elements like aluminium-26.

The simulations suggest that having these elements present in the planetesimals or building blocks of the new planet (and its neighbors), provided added heat that helps to evaporate most of the water, preventing a global ocean with an impenetrable layer of ice on the ocean floor from forming. This allows the carbon cycle to begin, which helps stabilize the climate and results in surface conditions favorable to life.

The important thing about this discovery isn't just that it sheds new light on how the Earth forms, but it will also help space scientists predict which exoplanets beyond our solar system are worth looking at for signs of life. By looking for the proper radioactive isotopes, it may be possible to predict whether a candidate planet is Earth-like or a giant ice world. In addition, a better understanding of the mechanism will help in calculating how many Earth-like worlds there are in the galaxy.

"It is great to know that radioactive elements can help make a wet system drier and to have an explanation as to why planets within the same system would share similar properties," says Meyer. "But radioactive heating may not be enough. How can we explain our Earth, which is very dry, indeed, compared to planets formed in our models? Perhaps having Jupiter where it is was also important in keeping most icy bodies out of the inner solar system."

The research was published in Nature Astronomy.

Source: University of Michigan

13 comments
Nobody
This is almost funny. There are so many special characteristics of earth that make it habitable for us that finding anything close is extremely unlikely. Astronomers know this but they are so intent on finding other habitable worlds that they ignore what is really necessary for life. I don't doubt that there could be other worlds similar to earth but they are extremely few. Probability calculations are useful tools but you can calculate a probability for something that will never happen.
Kpar
For a more complete picture on what is required for complex life, I highly recommend the book "Rare Earth" by Ward and Brownlee. This article only adds another confounding factor to that hypothesis. Astronomers have long been citing the Drake Equation for determining the likelihood of having neighboring civilizations in the stars. I have long felt that the Drake Equation is almost hopelessly optimistic- it only had about a dozen factors in the equation- lately I have heard that researchers have added about TWO HUNDRED MORE limiting factors, many based on the Rare Earth Hypothesis
michael_z
Nobody: Claiming it's "something that will never happen" is ridiculous when it has happened. Therefore, the odds of it happening are 1. Now, the odds of it happening twice are up for discussion. But Earth exists, therefore the criteria to make it happen provably also exist. AUTHOR: That would be supernova, not nova. Novae rarely emit more than gas and particles. Heavy elements are emitted in supernova explosions.
Signguy
What has and is becoming obvious to those who study the elements and the incredibly fine balance that the Earth exists in; as well as the cosmos and the life that exists on Earth is amazing and really a miracle of God's creation.
Nobody
michael_z, If you read again, I said I didn't doubt that there could be a few more earth like planets. I just said that probability does not necessarily prove it since we don't even know all the variables to enter. As we enter more conditions the probability gets smaller and smaller. You can even calculate the probability of every molecule of air will be in the other half of a room at the same time. As you add more molecules to the equation the probability gets increasingly smaller. You finally reach the point that it will never happen even though there is a tiny probability that it will.
Cryptonoetic
But, but... I thought CO2 was why the earth is warm. Now I'm being told it's because of *all natural* nuclear power? This is great news. Let's start building more *all natural* nuke plants so we can lower atmospheric CO2!
Thinker
I humbly submit the earth was a watery mess in the beginning. It was much larger in circumference and much hotter in the age of dinosaurs, it has been and still is cooling, not necessarily in the weather we experience today. During the Great Flood the earth cataclysmically contracted, thus in many cultures there is some remembrance of a great flood. When shrinkage takes place, tectonic plates move, and volcanoes explell the contents of the core. Me thinks much, not all scientific speculation is nonsense.
Wolf0579
I am so sick of religionists who haunt science sites (WHY?!?) and spew religious garbage in the comments sections. Grow up. There are no gods. Scientists who were brainwashed with religion as children have been looking for "god" since the invention of the scientific method. They have had zero success. I'm pretty confident when I say primitive humans could not and did not figure out the "creation" of the universe. Dump your primitive monkey religion. It only constrains your ability to imagine.
Nobody
Wolf0579, I seldom answer a comment like yours. I have degrees in chemistry and physics with quite a bit of computer programming and I am a Christian that believes in God. Most of my fellow scientists that I have worked with have the same beliefs. There has never been any conflict between my work and my religious beliefs. The chemical reactions and physics on the techniques I helped develop are the same whether you believe in God or not. I've spent 30 years computerizing chemical analyses and developing instruments so that tests can be run in seconds instead of hours. Many things from the food you eat to the car you drive have benefited from my work. I am not famous and most of my work is proprietary to the companies I worked for or advised. Science has never proven there is no God. Quite the contrary, since so many chemical and physical laws have to exist for us to exist, it could not be by accident. It is much more logical to believe that everything is by design and not an infinite number of coincidences that started with the big bang. Even among scientists who don't believe in God, they can't prove that their theories replace Him. The big bang is full of holes so they invented the inflation theory then dark matter and then dark energy none of which they can prove. As far as the original scientific method goes, something has to be repeatable and carried out by different researchers. The big bang and evolution will never be repeated so they will never be proven without stretching the true scientific method. So Wolf0579, I doubt that you have much if any real training in science. We all are free to believe what we wish. As for me, I am a scientist that has found God.
Stan Mitchell
Earth lost a lot of water because of solar electrolisis.the hydrogen escapes ,leaving oxygen.the author is probably wrong