Life May Extend Planet's 'Life': Billion-year Life Extension For Earth Also Doubles Odds Of Finding Life On Other Planets
2009 06 14

ScienceDaily.com

Roughly a billion years from now, the ever-increasing radiation from the sun will have heated Earth into inhabitability; the carbon dioxide in the atmosphere that serves as food for plant life will disappear, pulled out by the weathering of rocks; the oceans will evaporate; and all living things will disappear.

Or maybe not quite so soon, say researchers from the California Institute of Technology (Caltech), who have come up with a mechanism that doubles the future lifespan of the biosphere—while also increasing the chance that advanced life will be found elsewhere in the universe.
A paper describing their hypothesis was published June 1 in the early online edition of the Proceedings of the National Academy of Sciences (PNAS).
Earth maintains its surface temperatures through the greenhouse effect. Although the planet's greenhouse gases—chiefly water vapor, carbon dioxide, and methane—have become the villain in global warming scenarios, they're crucial for a habitable world, because they act as an insulating blanket in the atmosphere that absorbs and radiates thermal radiation, keeping the surface comfortably warm.


Roughly a billion years from now, the ever-increasing radiation from the sun will have heated Earth into inhabitability; the carbon dioxide in the atmosphere that serves as food for plant life will disappear, pulled out by the weathering of rocks; the oceans will evaporate; and all living things will disappear. Or maybe not quite so soon, researchers now say.


As the sun has matured over the past 4.5 billion years, it has become both brighter and hotter, increasing the amount of solar radiation received by Earth, along with surface temperatures. Earth has coped by reducing the amount of carbon dioxide in the atmosphere, thus reducing the warming effect. (Despite current concerns about rising carbon dioxide levels triggering detrimental climate change, the pressure of carbon dioxide in the atmosphere has dropped some 2,000-fold over the past 3.5 billion years; modern, man-made increases in atmospheric carbon dioxide offset a fraction of this overall decrease.)

The problem, says Joseph L. Kirschvink, the Nico and Marilyn Van Wingen Professor of Geobiology at Caltech and a coauthor of the PNAS paper, is that "we're nearing the point where there's not enough carbon dioxide left to regulate temperatures following the same procedures."

Kirschvink and his collaborators Yuk L. Yung, a Caltech professor of planetary science, and graduate students King-Fai Li and Kaveh Pahlevan, say that the solution is to reduce substantially the total pressure of the atmosphere itself, by removing massive amounts of molecular nitrogen, the largely nonreactive gas that makes up about 78 percent of the atmosphere. This would regulate the surface temperatures and allow carbon dioxide to remain in the atmosphere, to support life, and could tack an additional 1.3 billion years onto Earth's expected lifespan.

In the "blanket" analogy for greenhouse gases, carbon dioxide would be represented by the cotton fibers making up the blanket. "The cotton weave may have holes, which allow heat to leak out," explains Li, the lead author of the paper.

"The size of the holes is controlled by pressure," Yung says. "Squeeze the blanket," by increasing the atmospheric pressure, "and the holes become smaller, so less heat can escape. With less pressure, the holes become larger, and more heat can escape," he says, helping the planet to shed the extra heat generated by a more luminous sun.

Strikingly, no external influence would be necessary to take nitrogen out of the air, the scientists say. Instead, the biosphere itself would accomplish this, because nitrogen is incorporated into the cells of organisms as they grow, and is buried with them when they die.

In fact, "This reduction of nitrogen is something that may already be happening," says Pahlevan, and that has occurred over the course of Earth's history. This suggests that Earth's atmospheric pressure may be lower now than it was earlier in the planet's history.

Proof of this hypothesis may come from other research groups that are examining the gas bubbles formed in ancient lavas to determine past atmospheric pressure: the maximum size of a forming bubble is constrained by the amount of atmospheric pressure, with higher pressures producing smaller bubbles, and vice versa.

If true, the mechanism also would potentially occur on any extrasolar planet with an atmosphere and a biosphere.

"Hopefully, in the future we will not only detect Earth-like planets around other stars but learn something about their atmospheres and the ambient pressures," Pahlevan says. "And if it turns out that older planets tend to have thinner atmospheres, it would be an indication that this process has some universality."

Adds Yung: "We can't wait for the experiment to occur on Earth. It would take too long. But if we study exoplanets, maybe we will see it. Maybe the experiment has already been done."

Increasing the lifespan of our biosphere—from roughly 1 billion to 2.3 billion years—has intriguing implications for the search for life elsewhere in the universe. The length of the existence of advanced life is a variable in the Drake equation, astronomer Frank Drake's famous formula for estimating the number of intelligent extraterrestrial civilizations in the galaxy. Doubling the duration of Earth's biosphere effectively doubles the odds that intelligent life will be found elsewhere in the galaxy.

"It didn't take very long to produce life on the planet, but it takes a very long time to develop advanced life," says Yung. On Earth, this process took four billion years. "Adding an additional billion years gives us more time to develop, and more time to encounter advanced civilizations, whose own existence might be prolonged by this mechanism. It gives us a chance to meet."




Related Articles
Ocean-bearing Planets: Looking For Extraterrestrial Life In All The Right Places
What Are The Odds Of Finding Extraterrestrial Intelligent Life?
NASA Takes Giant Step Toward Finding Earth-Like Planets


Latest News from our Front Page

Tiny Micro Robots Build Things in ‘Microfactory’
2014 04 17
The teenie-weeniest robot uprising ever might be sooner rather than later due to the work of research institute SRI. Don’t let these microbots’ size fool you, there is power in numbers and thousands of the robots can work together to perform tasks at dizzying speed. From ReCode.net: SRI International has developed a new generation of ant-like robots that can work as ...
’We are not dead yet’: Heartbreaking text messages sent from schoolchildren trapped aboard South Korean ferry
2014 04 17
Passengers on board the South Korean ferry sent heartbreaking messages to their family members just moments before it sank. Children waiting to be rescued frantically reached for their phones as the boat began to list in a bid to communicate with their loved ones a final time. Twenty-four people, including five students and two teachers, have been found dead, but 272 are ...
"A world of pure imagination": How Occupy turned to "anarchy"
2014 04 17
In the closing ceremonies of London’s 2012 Summer Olympics, comedian Russell Brand, perched atop the Beatles’ "Magical Mystery Tour" bus, opened his performance by singing the first lines of "Pure Imagination" from the movie Willy Wonka: Come with me And you’ll be In a world of Pure imagination ...
Artists ’have structurally different brains’
2014 04 17
Artists have structurally different brains compared with non-artists, a study has found. Participants’ brain scans revealed that artists had increased neural matter in areas relating to fine motor movements and visual imagery. The research, published in NeuroImage, suggests that an artist’s talent could be innate. But training and environmental upbringing also play crucial roles in their ability, the authors report. As in many areas ...
NSA-proof email service goes online
2014 04 17
A new email service that protects its users from the prying eyes of the NSA and other spy agencies has gone online. The service’s creators say it will make encrypted messaging accessible to all and curtail internet snooping. Germany-based Lavaboom was inspired by Lavabit, the encrypted email service that was believed to have been used by whistleblower Edward Snowden before it ...
More News »