"Alien Solar Systems May Prove to be More Habitable than Ours"
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December 04, 2012

"Alien Solar Systems May Prove to be More Habitable than Ours"

 

 

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Scattered around the Milky Way are stars that resemble our own sun—but a new study is finding that any planets orbiting those stars may very well be hotter and more dynamic than Earth because the interiors of terrestrial planets in these systems are likely warmer than Earth by up to 25 percent, which would make them more geologically active and more likely to retain enough liquid water to support life, at least in its microbial form. The finding comes from geologists and astronomers at Ohio State University who have teamed up to search for alien life in a new way.

The Ohio State team studied eight “solar twins” of our sun—stars that very closely match the sun in size, age, and overall composition—in order to measure the amounts of radioactive elements they contain. Those stars came from a dataset recorded by the High Accuracy Radial Velocity Planet Searcher spectrometer at the European Southern Observatory in Chile (image above). They searched the solar twins for elements such as thorium and uranium, which are essential to Earth’s plate tectonics because they warm our planet’s interior. Plate tectonics helps maintain water on the surface of the Earth, so the existence of plate tectonics is sometimes taken as an indicator of a planet’s hospitality to life.

Of the eight solar twins they’ve studied so far, seven appear to contain much more thorium than our sun—which suggests that any planets orbiting those stars probably contain more thorium, too. That, in turn, means that the interior of the planets are probably warmer than ours. One star in the survey contains 2.5 times more thorium than our sun, said Ohio State doctoral student Cayman Unterborn. According to his measurements, terrestrial planets that formed around that star probably generate 25 percent more internal heat than Earth does, allowing for plate tectonics to persist longer through a planet’s history, giving more time for live to arise.

“If it turns out that these planets are warmer than we previously thought, then we can effectively increase the size of the habitable zone around these stars by pushing the habitable zone farther from the host star, and consider more of those planets hospitable to microbial life,” said Unterborn, who presented the results at the American Geophysical Union meeting in San Francisco this week. “If it turns out that these planets are warmer than we previously thought, then we can effectively increase the size of the habitable zone around these stars...”

“At this point, all we can say for sure is that there is some natural variation in the amount of radioactive elements inside stars like ours,” he added. “With only nine samples including the sun, we can’t say much about the full extent of that variation throughout the galaxy. But from what we know about planet formation, we do know that the planets around those stars probably exhibit the same variation, which has implications for the possibility of life.”

Wendy Panero, associate professor in the School of Earth Sciences at Ohio State, explained that radioactive elements such as thorium, uranium, and potassium are present within Earth’s mantle. These elements heat the planet from the inside, in a way that is completely separate from the heat emanating from Earth’s core.

“The core is hot because it started out hot,” Panero said. “But the core isn’t our only heat source. A comparable contributor is the slow radioactive decay of elements that were here when the Earth formed. Without radioactivity, there wouldn’t be enough heat to drive the plate tectonics that maintains surface oceans on Earth.”

The relationship between plate tectonics and surface water is complex and not completely understood. Panero called it “one of the great mysteries in the geosciences.” But researchers are beginning to suspect that the same forces of heat convection in the mantle that move Earth’s crust somehow regulate the amount of water in the oceans, too.

“It seems that if a planet is to retain an ocean over geologic timescales, it needs some kind of crust ‘recycling system,’ and for us that’s mantle convection,” Unterborn said.

In particular, microbial life on Earth benefits from subsurface heat. Scores of microbes known as archaea do not rely on the sun for energy, but instead live directly off of heat arising from deep inside the Earth, where most of the heat from radioactive decay comes from uranium. Planets rich in thorium, which is more energetic than uranium and has a longer half-life, would “run” hotter and remain hot longer, he said, which gives them more time to develop life.

“It all starts with supernovae. The elements created in a supernova determine the materials that are available for new stars and planets to form. The solar twins we studied are scattered around the galaxy, so they all formed from different supernovae. It just so happens that they had more thorium available when they formed than we did.”

Jennifer Johnson, associate professor of astronomy at Ohio State and co-author of the study, cautioned that the results are preliminary. “All signs are pointing to yes—that there is a difference in the abundance of radioactive elements in these stars, but we need to see how robust the result is,” she said.

Next, Unterborn wants to do a detailed statistical analysis of noise in the HARPS data to improve the accuracy of his computer models. Then he will seek telescope time to look for more solar twins.

The Daily Galaxy via http://researchnews.osu.edu

Comments

I am sure impressively beautiful paradises, not dreamed or even imagined, are out there waiting for our visit, and the beginning of the decline.

Now that someone mentions it, this seems obvious. Naturally produced elements heavier than about iron or nickel have to be made in supernovae. While uranium and thorium have isotopes with long half-lives, significant amounts of both should decay over billions of years. Holding metallicity constant, star systems made from residue of more recent supernovae should have higher uranium and thorium levels. This should lead to greater heat generation from radioactive decay. Therefore otherwise icy planets could have geothermally active zones teaming with life or that could support human settlement. Just be careful of radon levels.

Under the mediocrity principle, this is a given. Together with the sheer number of stars in our galaxy alone, let alone the visible universe (not to even mention the universe beyond what's in our light cone and therefore visible), the chances that a system exists in which many planets are not just habitable but veritable paradises approaches one.

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Therefore otherwise icy planets could have geothermally active zones teaming with life or that could support human settlement. Just be careful of radon levels.

We just keep getting closer and closer to finding a planet that would be hospitable to human life. Hopefully we won't get so excited about it that we send a manned mission as soon as we have the technology. If we can send a robotic probe to explore such things as the ecosystem's biochemistry first, we'll be able to tell if it's safe, including whether the animal life there would be edible and domesticable.

Also, by the time we're able to do actual colonization, I expect we'll have learned from the ecological mistakes of the past. If nothing else, if we haven't learned by then, we probably won't be around to continue making them on other planets.

BUT................what are we going to do about the same thing that killed the Martians in 'War of the Worlds?"

Nice topic but think we should put more effert to engineering faster more efficient safe for radiation means of travel engine wise and ship. Also equip it with more and adaptable features and prob lunch capability then we could Ravel far study and launch a separate study with prob for multi outcome. I have a few ideas on how but it's my dream for now.


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