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

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

Norway Joins the Race to Develop Killer Robots
2014 10 24
Norway is a large exporter of weapons, which makes the resolution of the debate about creating killer robots an important issue for everyone.  One could debate the overall merits or failings of robotic systems, but an area that clearly has become a point for concern on all sides is the emergence of "killer robots." According to robotics pioneer, David Hanson, ...
Gene That Once Aided Survival in the Arctic Found to Have Negative Impact on Health Today
2014 10 23
In individuals living in the Arctic, researchers have discovered a gene variant that arose thousands of years ago and most likely provided an evolutionary advantage for processing high-fat diets or for surviving in a cold environment; however, the variant also seems to increase the risk of hypoglycemia, or low blood sugar, and infant mortality in today’s northern populations. {snip} “Our work ...
The Ebola hoax: questions, answers, and the false belief in the “One It”
2014 10 23
“The Reality Manufacturing Company doesn’t just sell ‘fake paintings’ that are easy to spot. No. They also sell images that are geared to mesh with people’s deeply held instincts and thereby produce rigid false beliefs. People are sure that if they gave up such beliefs, their world would fall apart and blow away in the wind.” ...
New Controversial Theory Suggests "Hobbits" Were Not Human - Who Were These Mysterious Beings?
2014 10 23
The origin of the Hobbit species remains a challenging subject to scientists. The Hobbit’s discovery confirmed the view that the Earth was once populated by many species of human, but new research the Hobbit’s were not human at all! So, who were these mysterious beings? Where did they come from? The idea that our species, Homo sapiens, was the only species of human on ...
Right into enemy hands? ISIS shows off new weapons allegedly airdropped by US (VIDEO)
2014 10 23
Islamic State has published a new video in which a jihadist shows off brand-new American hardware, which was purportedly intended for the Kurds they are fighting in the Syrian border town of Kobani. The undated video, posted by the unofficial IS mouthpiece “a3maq news”, sees a jihadist showing several boxes of munitions with English-language markings, with a parachute spread out on ...
More News »