'Totally New' Idea Suggests Longer Days On Early Earth Set Stage For Complex Life (sciencemag.org) 27
"A research team has proposed a novel link between how fast our planet spun on its axis, which defines the length of a day, and the ancient production of additional oxygen," reports Science Magazine. "Their modeling of Earth's early days, which incorporates evidence from microbial mats coating the bottom of a shallow, sunlit sinkhole in Lake Huron, produced a surprising conclusion: as Earth's spin slowed, the resulting longer days could have triggered more photosynthesis from similar mats, allowing oxygen to build up in ancient seas and diffuse up into the atmosphere." From the report: As a postdoc at the University of Michigan, Ann Arbor, Klatt had studied microbial mats growing on sediments in the Middle Island Sinkhole in Lake Huron. There, the water is shallow enough for the cyanobacteria to get enough sunlight for photosynthesis. Oxygen-depleted water and sulfur gas bubble up from the lake floor, creating anoxic conditions that roughly approximate conditions of early Earth. Scuba divers collected samples of the microbial mats and in the lab, Klatt tracked the amount of oxygen they released under various day lengths simulated with halogen lamps. The longer the exposure to light, the more of the gas the mats released.
Excited, Klatt and Arjun Chennu, a modeler from the Leibniz Center for Tropical Marine Research, set up a numerical model to calculate how much oxygen ancient cyanobacteria could have produced on a global scale. When the microbial mat results and other data were plugged into this computer program, it revealed a key interaction between light exposure and the microbial mats. Typically, microbial mats "breathe" in almost as much oxygen at night as they produce during the day. But as Earth's spin slowed, the additional continuous hours of daylight allowed the simulated mats to build up a surplus, releasing oxygen into the water. As a result, atmospheric oxygen tracked estimated day length over the eons: Both rose in a stepped fashion with a long plateau.
This "elegant" idea helps explain why oxygen didn't build up in the atmosphere as soon as cyanobacteria appeared on the scene 3.5 billion years ago, says Timothy Lyons, a biogeochemist at the University of California, Riverside. Because day length was still so short back then, oxygen in the mats never had a chance to build up enough to diffuse out. "Long daytimes simply allow more oxygen to escape to the overlying waters and eventually the atmosphere," Lyons says. Still, Lyons and others say, many factors likely contributed to the rise in oxygen. For example, Fischer suspects free-floating cyanobacteria, not just those in rock-affixed mats, were big players. Benjamin Mills, an Earth system modeler at the University of Leeds, thinks the release of oxygen-binding minerals by ancient volcanoes likely countered the early buildup of the gas at times and should be factored into oxygen calculations. Nonetheless, changing day length "is something that should be considered in more detail," he says. "I'll try to add it to our Earth system models."
Excited, Klatt and Arjun Chennu, a modeler from the Leibniz Center for Tropical Marine Research, set up a numerical model to calculate how much oxygen ancient cyanobacteria could have produced on a global scale. When the microbial mat results and other data were plugged into this computer program, it revealed a key interaction between light exposure and the microbial mats. Typically, microbial mats "breathe" in almost as much oxygen at night as they produce during the day. But as Earth's spin slowed, the additional continuous hours of daylight allowed the simulated mats to build up a surplus, releasing oxygen into the water. As a result, atmospheric oxygen tracked estimated day length over the eons: Both rose in a stepped fashion with a long plateau.
This "elegant" idea helps explain why oxygen didn't build up in the atmosphere as soon as cyanobacteria appeared on the scene 3.5 billion years ago, says Timothy Lyons, a biogeochemist at the University of California, Riverside. Because day length was still so short back then, oxygen in the mats never had a chance to build up enough to diffuse out. "Long daytimes simply allow more oxygen to escape to the overlying waters and eventually the atmosphere," Lyons says. Still, Lyons and others say, many factors likely contributed to the rise in oxygen. For example, Fischer suspects free-floating cyanobacteria, not just those in rock-affixed mats, were big players. Benjamin Mills, an Earth system modeler at the University of Leeds, thinks the release of oxygen-binding minerals by ancient volcanoes likely countered the early buildup of the gas at times and should be factored into oxygen calculations. Nonetheless, changing day length "is something that should be considered in more detail," he says. "I'll try to add it to our Earth system models."
Let me guess (Score:2)
They want to hit the brake to check their theory?
The sun was also dimmer back then (Score:3)
Dimmer sun = less efficient photosynthesis
Re: (Score:2)
1. I was under the impression that Stars shine brighter when they are younger.
2. A lot of photosynthesis based life plants, algae and microbes when exposed to too much sun (even on current earth) they will burn or dry up. They actually thrive better in shade. More evolved plants like trees, have adapted coping mechanisms to deal with a full sun.
3. Conditions like clouds, mountains, competing plants, ocean depths, as well latitude on the earth, are often much larger factors than a few percentages in power o
Re:The sun was also dimmer back then (Score:5, Informative)
1. Nope. The sun is getting brighter as it gets older.
3. More than a few percent:
https://faculty.wcas.northwest... [northwestern.edu]
"when the Sun was formed 4.5 billion years ago it was about 30% dimmer than at present"
Re: (Score:1)
Given there is evidence of of significant impacts we can assume that our proximity to the sun has changed over time.
Re: (Score:2)
If it has its nothing to do with impacts. An asteroid hitting the earth is equivalent to a fly hitting a truck.
Re: (Score:1)
Come now your making some big assumptions about of the object that collided, as far as I am aware the Sumarian's recorded a story of an impact by a very large moon which was deflected, an impact with a planet/moon of significant size compared to our planet and was a deflected could have easily taken place. And we haven't even started to consider the relative speeds, angles of trajectory, impact surface size, atmosphere of the the interstellar body which we collided with. To think that our Rotation, our traj
Re: (Score:2)
When the dinosaurs were around, the earth was alot warmer, however, earth has had some notably long ice-ages -- most recently a small one, ~1700's could have been thought to have been indirectly responsible for the industrial revolution and an uptick in CO2. Could humans be part of that global-c
Re: (Score:2)
For a star of the Sun's mass, it brightens at about 5% per gigayear. [wikipedia.org] As the star fuses hydrogen into helium, the mean mass of nuclear particles in the core increases (because 4 particles at mass 1 merge to form 1 particle of mass 3.98) and that requires the core temperature to increase to maintain pressure equilibrium. Higher core temperature produces more fusion.
Where did you get the idea that young stars are brighter? The o
You rarely go wrong with totally new ideas. (Score:2)
Re:You rarely go wrong with totally new ideas. (Score:4, Insightful)
Global Cooling is valid - The next ice-age would be underway without man's activities having reversed it. We've managed to override the natural rhythm. Which likely makes the looming catastrophe an even bigger hammer because of the extra energy required to flip its inertia.
Seasons (Score:2)
The early Earth still had an axial tilt and seasons, right? So shouldn't the northern and southern areas already have had long summer days, months of daylight at the poles? Are the tropics that much more important for some reason?
Re: (Score:2)
Have a read of the linked article.
They're taking about the length of the whole day (light and dark combined) being as little as a few hours, then growing at something like a linear rate to about 16 hours. Then, oddly, flatlining for nearly 1.5 billion years before again resuming the increase in longer days just 750 million years ago.
There is no explanation for that particular profile though. And given the moon's tidal drag is meant to be the driving force for lengthening days, I struggle to see how they c
Re: (Score:2)
Err, the graph shows the pause at 18 hour days rather.
Re: (Score:2)
I've got to RTFA too, but I can address that point from past studies.
The angular momentum of the Earth is being transferred to the orbit of the moon around the Earth through the medium of the drag of the ocean bottom on the oceans' two tidal bulges, which are dragged ahead of the line joining the Earth and Moon's centres. If the Earth (and Moon) were perfectly smooth rock spheres without irregularity, the tidal drag forces would evolve steadily, b
Slowdown due to formation of the moon (Score:3)
Evidence is the moon broke off from young earth after a catastrophic collision with a large object.
My understanding til now was this happened at a time when earth was still too hot to allow any life, including these bacteria.
But maybe this idea is more about earth slowing down over a longer period of time, sufficient to allow the first bacteria to develop before the slowdown became significant.
Re: (Score:2)
What they're proposing is a relatively fast slowdown but then with a 1.5 billion year pause before resuming the slowdown quite late at just 750 millions years ago. It seems very concocted to me.
The tides slow down the earth (Score:2)
It is still slowing, and the moon is getting further away.
So when we make tidal electricity, we are destroying the Moon, just like solar energy kills the sun...
Makes no sense (Score:2)
This just smells like total bollocks to me
Re: (Score:3)
Re: (Score:2)
TFS makes no sense to me...
A "longer day" at place X also means a longer NIGHT at place Y. So, great, X gets to produce more O2 - but only at the expense of Y. On the surface, this is clearly a zero-sum game. What's the special magic that somehow makes it not so?
Re: (Score:3)
Plants are a bit more complex than "light on