14 DAY TRIAL // Astronomers have known for a long time that the Sun is currently at the middle of its life cycle, having already burnt for more than 4.6 billion years. As a yellow main sequence star, it is expected to live a full life of about 10 billion years, but naturally, during this time, it will evolve. Sadly for Earth, this implies it expanding as it turns into a red supergiant, eventually engulfing the entire planet within its mass. Things are considered to start getting pretty worse in about one billion years, when astronomers believe the heat will be so great that our planet will become uninhabitable.
However, this theory has recently been contested by a group of experts from the California Institute of Technology (Caltech), who say that we could make the planet able to support life even beyond the 1 billion years marker currently theorized. But, in order to do that, we'd have to get into some pretty serious geoengineering schemes. The scientists say that the best way to prevent temperatures from skyrocketing and oceans from evaporating is to simply pump out vast amounts of nitrogen from our planet's atmosphere, which is mostly made up of the stuff.
In a study published online in the June 1st issue of the journal Proceedings of the National Academy of Sciences (PNAS), the Caltech team showed that the concentrations of carbon dioxide (CO2), the main greenhouse gas responsible for global warming, had actually been decreasing for the past 3.5 billion years. That is to say, the pressure the gas exerts in the atmosphere is becoming ever-smaller; on the other hand, it is the main compound that regulates the amount of heat the atmosphere gets, and also determines how much of it the air disperses.
“We're nearing the point where there's not enough carbon dioxide left to regulate temperatures following the same procedures,” says a co-author of the PNAS paper, the Caltech Nico and Marilyn Van Wingen Professor of Geobiology, Joseph L. Kirschvink. Together with a number of colleagues, the expert believes that the only solution we may have of making our planet inhabitable for, say, the next two billion years, would be to decrease its overall pressure, rather than increase that of CO2. The move could add another 1.3 billion years of lifespan to the planet, and would allow it to retain its oceans, ecosystems, vegetation, and possibly human populations, for longer too.
The team likens the carbon dioxide with the weaves on a cotton blanket. “The cotton weave may have holes, which allow heat to leak out,” says graduate student King-Fai Li, the lead author of the new paper. “The size of the holes is controlled by pressure. Squeeze the blanket and the holes become smaller, so less heat can escape. With less pressure, the holes become larger, and more heat can escape,” adds Caltech professor of planetary science Yuk L. Yung, who collaborated with Kirschvink for the new research.
The team says that the reduction process of atmospheric nitrogen may already be underway. The compound is naturally drawn into living things when they are born, and is then buried in the ground when they die. This means that it may not even take a global effort of pumping nitrogen out of the atmosphere, but simply an intervention to boost the planet's natural abilities of doing just that. The experts believe that the pressure currently being recorded in the atmosphere is, in fact, significantly lower than it was when the planet was first formed, some 4.5 billion years ago.
“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. And if it turns out that older planets tend to have thinner atmospheres, it would be an indication that this process has some universality,” explains Kaveh Pahlevan, also a graduate student at Caltech. “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,” Yung argues.
“It didn't take very long to produce life on the planet, but it takes a very long time to develop advanced life. 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,” he adds, highlighting the fact that it took well over four billion years for intelligent life to develop on Earth, to the point where we came along.