The Mystery of Earth's Oxygen

I read the article The Mystery of Earth’s Oxygen by Carl Zimmer. This article talked about research that Dr. Canfield, a geochemist at the University of Southern Denmark, did along with his colleagues regarding Earth’s changing oxygen supply. To know whether we are at risk of a dwindling supply of oxygen, the scientists look at rocks in order to examine the chemical fingerprints left behind. They know that certain rocks could have only formed in the presence of oxygen, and from there they can conclude that the more of these molecules found, the more oxygen was present in the air during the formation. When they look at the oldest rocks on earth, there are no traces of oxygen, and research points to the conclusion that earth’s atmosphere had been made of mostly carbon dioxide, methane, and nitrogen. Although the sun had produced oxygen, it dispersed as soon as it was formed. Because oxygen is highly reactive, it bonds easily with other molecules so Earth was like “a giant oxygen volume in its early years.” Evidence shows that three billion years ago the atmosphere had only 0.03 percent of today’s oxygen levels. That was a huge shift in the Earth’s chemistry, because sunlight couldn't have produced that much light, only life could have. Microbes photosynthesized, creating the oxygen, and when they died, they sank to the bottom where the oxygen couldn't react with their carbon, so the oxygen remained. From there it was said that the oxygen source remained fairly scarce for the next few hundred million years, but during that period, Earth’s vacuum was getting weaker. In addition Earth was cooling, so there was less volcanic movement, so not as much Hydrogen was produced to react with the oxygen. And then once again, the oxygen levels declined when carbon rich rocks were created from the microbes on the sea floor, which were brought up to dry land, and reacted with the oxygen.

                This research is directly linked to our lives, and is relevant so we can know how much longer our oxygen levels will stay stable. Over the past two billion years, life and earth have had the oxygen levels bouncing around and not constant. This creates a scare because today as forests shrink, oxygen levels become lower, and makes our future unpredictable. The question that this situation arises is whether Earth’s oxygen supply will remain or begin to decline again. This leaves us worried as to how long our oxygen supply will last.

                I think the author did a really good job of explaining Earth’s atmosphere in the past, and how the oxygen levels have changes with time. I really liked how much information was put behind how they know about the changing oxygen levels. I wish that the author had included more information about what objects today are acting as vacuums, sucking up the oxygen gas, and whether that is something we can change or not. I also wish there had been ways we can help, aside from stop cutting down forests and plant trees, to keep our oxygen level high. Also I wanted to know if our population continues to grow, whether it will affect the oxygen levels, since so much oxygen is being taken in. 

http://www.nytimes.com/2013/10/03/science/earths-oxygen-a-mystery-easy-to-take-for-granted.html?ref=science