Increases in Oxygen Prepare Earth for Complex Life

Increases in Oxygen Prepare Earth for Complex Life

June 30th, 2010

By Dr. Jeff Zweerink

One of Earth’s most remarkable attributes is the permanent oxygen component of the planet’s atmosphere. Oxygen’s reactivity makes it an efficient energy source for life, but it also means oxygen would disappear quickly without a continuous resupply. Atmospheric oxygen increased dramatically during two different periods in Earth’s history. Yet these increases occurred only because of a complex and elegant interplay of geological, astronomical, biological, atmospheric, and chemical processes.

For most of Earth’s history its atmosphere contained no oxygen. Then, just over two billion years ago, oxygen gained a permanent foothold, though at a fraction of today’s concentrations. Even greater jumps in oxygen content occurred between 600 and 800 million years ago. These jumps resulted in long-standing consequences. First, they were often accompanied by intense ice ages where glaciers advanced close to the equator. Scientists believe these aptly-named “snowball Earth” events may have occurred because increased oxygen levels converted methane, a strong atmospheric greenhouse gas, into the less potent carbon dioxide. As catastrophic as these snowball events were, the changes in Earth’s atmosphere were necessary to compensate for the Sun’s steadily increasing luminosity. Fortunately, aspects of biological activity prevented the glaciations from destroying Earth’s capacity to support life.

Most importantly, the oxygen jumps ushered in a dramatic rise in life’s complexity. Previous research indicated that changes in the plate tectonic activity—specifically the first formation of tall mountains—increased the supply of molybdenum to the oceans and that, in turn, boosted biological activity.

Now it appears that the changes in biological activity (both the increase in number and complexity) also required a boosted phosphorous supply. According to research recently published in Astrobiology, phosphorite deposits across the globe correspond to Earth’s two great oxygenation events.1 The model outlined in the paper argues that tectonic processes produced a greater (and higher) continental landmass. The weathering of this landmass transported phosphorous to the oceans, causing a dramatic rise in primary biological production. After the last increase in oxygen around 650 million years ago Earth could finally support complex, multicellular organisms.

We at RTB argue that any mechanism exhibiting complex, integrated actions that bring about a specified outcome is designed. Studies of Earth’s history reveal highly orchestrated interplay between astronomical, geological, biological, atmospheric, and chemical processes that transform the planet from an uninhabitable wasteland to a place teeming with advanced life. The implications of design are overwhelming.

Endnotes:
1. Dominic Papineau, “Global Biogeochemical Changes at Both Ends of the Proterozoic: Insights from Phosphorites,” Astrobiology 10 (April 19, 2010): 165–81.

Too Much Oxygen in the Past

September 22nd, 2010

By Dr. Jeff Zweerink

Oxygen Spikes Jumpstart Life's Complexity and Size

March 1st, 2010

By Dr. Jeff Zweerink

Since life first appeared on Earth, the size of the largest organisms increased in size by a factor of 10 quadrillion (1016 or 10,000,000,000,000,000). Two sudden bursts, each showing an organism volume increase by a factor of one million (106), account for most this growth.1Both bursts occurred after a significant change in the quantity of oxygen in Earth’s atmosphere. The latter oxygenation event occurred just prior to the Cambrian explosion. Research into the timing and stability of the first oxygenation event provides more evidence supporting RTB’s creation model, which predicts that complex life would appear suddenly and early in Earth’s history.

Timing of First Oxygenation Event

The geological column records the history of how life changed as time progressed. A number of geological signatures indicate oxygen appeared as a permanent component in Earth’s atmosphere 2.4 billion years ago. However, evidence shows that photosynthetic organisms arrived on the scene at least 100 million years earlier. Studies of nitrogen cycling may explain the delay.2

The presence of oxygen affects how nitrogen interacts with its environment. Lacking oxygen, a specific ratio of nitrogen isotopes is deposited on the ocean floor. Adding oxygen to the mix will increase the amount of heavier nitrogen (15N) compared to lighter nitrogen (14N and 13N). Around 2.7 billion years ago, the amount of heavier nitrogen increased by a detectable amount, providing evidence that photosynthetic organisms were producing oxygen.

A second increase 150 million years later indicates that the nitrogen cycle changed again, thus demonstrating some instability. During this latter increase the amount of “fixed” nitrogen decreased. Many organisms cannot use atmospheric nitrogen (N2) for energy production but rely on “fixed” nitrogen, primarily in the form of ammonia. The lack of fixed nitrogen then limits the productivity of the photosynthetic organisms, keeping the amount of oxygen in the atmosphere low.

This research highlights how difficult it is to effect major changes in a planet’s atmospheric chemistry. Even with the advent of oxygen producing organisms, a permanent component of atmospheric oxygen was delayed hundreds of millions of years––suggesting that the agent of change was beyond natural.

Stability of First Oxygenation Event

Most geological signatures point to the arrival of eukaryotes (animals, plants, fungi) on Earth around 1.6–2.1 billion years ago. In contrast to the prokaryotes (bacteria, archaea) dating back to 3.8 billion years, eukaryotes exhibit far more internal structure and can grow much larger. It was the advent of eukaryotes that accounts for the first rapid increase of organism size.

Even though a growing body of evidence shows that Earth’s atmosphere contained oxygen starting 2.4 billion years ago, more detailed studies hint at instabilities during its initial stages.3This instability may explain why the first dramatic increase in organism size and complexity did not occur for roughly half-a-billion years after the first appearance of oxygen.

Evidence for this atmospheric oxygen instability comes from the same element that makes (old) bumpers shine and steel stainless, namely chromium. In an atmosphere without oxygen, chromium remains locked in the continental crust. In the presence of oxygen, chemical reactions extract chromium and lead to weathering processes that then transport it to the ocean. Additionally, these processes alter chromium’s isotopic composition in a way that can be used to trace the presence of oxygen in the atmosphere.

A team of scientists analyzed these chromium isotopes in ancient sea sediments. Their research revealed chromium isotope fractionation in formations deposited before the great oxygenation event around 2.4 billion years ago. This find indicates that the oxygen levels rose for a geologically brief period of time (a couple million years). However, in more recent formations, around 1.9 billion years ago, no fractionation occurs, pointing to a lack of oxygen in Earth’s atmosphere. Over the next hundred million years atmospheric oxygen permanently increased, preceding the appearance of eukaryotic life and the associated factor of a million jump in body size.

If naturalistic processes triggered the formation of the more complex eukaryotic life, scientists would expect to see some fossil traces of eukaryotes during the earlier increases in oxygen. Instead, eukaryotes don’t appear until oxygen gains a permanent foothold in the atmosphere. This exquisite timing is consistent with the notion of a carefully designed plan to bring about a planet maximized for human habitability.
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1 Jonathan L. Payne et al., “Two-phase Increase in the Maximum Size of Life over 3.5 Billion Years Reflects Biological Innovation and Environmental Opportunity,” Proceedings of the National Academy of Sciences, USA 106 (January 6, 2009): 24–27.

2 Linda V. Godfrey and Paul G. Falkowski, “The Cycling and Redox State of Nitrogen in the Archaean Ocean,” Nature Geoscience 2 (October 1, 2009): 725–29.

3 Robert Frei et al., “Fluctuations in Precambrian Atmospheric Oxygenation Recorded by Chromium Isotopes,” Nature 461 (September 10, 2009): 250–53.

Subjects: Geophysical Design

“This fire needs more wood!” said my oldest daughter as we sat around the campfire after setting up in the rain. I couldn’t agree more.

One of my favorite activities is roasting s’mores over the campfire in the cool of the evening. Everyone knows you need graham crackers, chocolate squares, and marshmallows to make s’mores. But one essential “ingredient” that often goes unnoticed is the atmosphere’s oxygen content. For the last 50 million years, this important gas comprised 20 percent of the atmosphere. New research indicates that this value fluctuated dramatically in earlier times.

Attempts to measure Earth’s past oxygen content often give conflicting results. This difficulty arises because scientists cannot directly measure the ancient atmospheric gases but must use proxies instead. Numerous variables affect the geological record, oxygen being just one of those variables. However, a team of scientists recently found a way to control for all the other variables by using coal as a proxy for past oxygen content.

Without oxygen, nothing burns—but with enough oxygen, even wet objects readily combust. Thus, the researchers were able to use charcoal (burned organic matter) formed in water-rich environments as the proxy. The amount of charcoal in coal depends primarily on the amount of gaseous oxygen available and coal’s economic value means a large database of charcoal compositions already exists. The information in this database demonstrates that even with dramatic climate changes over the last few million years the amount of coal remained relatively uniform. This matches the expectation that the oxygen content of the atmosphere remained constant over the past 50 million years.

However, over the last 400 million years, the oxygen showed dramatic increases and decreases compared to current values.1 Past life on Earth may have been well adapted to these changes, but similar changes today would cause significant problems for humanity. Too much oxygen in the atmosphere leads to explosive and destructive wildfires. Too little oxygen means less energy is available to fuel biochemical reactions inside large-bodied organisms, like humans.

An increasing body of evidence shows that Earth’s environment changed numerous times in ways that altered the kinds of life able to survive on the planet. Yet humanity arrived on the scene during a stable period when the atmospheric oxygen met all the criteria that advanced life requires. Such fine-timing follows if a supernatural Designer is preparing a place for human life.

Subjects: Geophysical Design

More Evidence for the Design of Earthquake Activity

August 18th, 2008

By Dr. Hugh Ross

Faulting, generated by active and widespread tectonics, allowed a youthful Earth to support diverse and abundant life.

In the December 2007 issue of Astrobiology Stanford University geophysicists Norman H. Sleep and Mark D. Zoback note that the higher tectonic activity during Earth’s early history could have played a key role in cycling critically important nutrients and energy sources for life.1 The production of numerous small faults in the brittle primordial crust released trapped nutrients. Such faults could also release pockets of methane gas and molecular hydrogen. The methane and hydrogen could then provide crucial energy sources for nonphotosynthetic life. Finally, the production of faults could bring water to otherwise arid habitats, such as rocks far below Earth’s surface.

Faulting, generated by active and widespread tectonics, allowed a youthful Earth to support diverse and abundant life. This enhanced diversity and abundance of life quickly transformed Earth’s surface into an environment safe for advanced life. Also, the buildup of biodeposits for the support of human civilization occurred more rapidly due to active tectonics.

The more rapid preparation of Earth for humanity is critical. Without such rapid preparation, humans could not come upon the terrestrial scene before the Sun’s increasing luminosity would make their presence impossible (due to excessive heat).2 Thus, yet one more reason exists to thank God for His supernatural design of Earth’s tectonics.

Subjects: Biodeposits, Extrasolar Planets, First Life on Earth, Geophysical Design, Habitable Planets, Natural Disasters, Plate Tectonics, Solar System Design, TCM - Cosmic Design

Subduction Design

November 3rd, 2008

By Phil Chien

11/3/2008
by Dr. Hugh Ross

Stanford University geophysicist Norman Sleep has outlined some new constraints on habitable planets.1 He explains how the possible existence of advanced life crucially depends upon a planet maintaining efficient plate tectonics for billions of years. Without such plate tectonics several nutrient-recycling processes, critical for advanced life, cannot be sustained. Efficient plate tectonics are also essential for transforming a planet’s surface into a mix of oceans and continents.

Both the nutrient recycling and the development of continental landmasses require a high rate of subduction. Subduction is the sliding of one tectonic plate under another. For subduction to take place, the tectonic plates need to slip in friction at the fault zones. Also, the lithosphere within the crustal slab that is slipping under another crustal slab needs to bend with a specified strain.

An overarching design requirement for advanced life, then, is that the rate of subduction must be fine-tuned. Too low of a subduction rate would lead to inadequate nutrient recycling and inadequate buildup of continents. (If the buildup rate is much less than the erosion rate, the continents will disappear.) Too high of a subduction rate would disturb the ecosystems of advanced life and challenge the development of global high-technology civilization.

To sustain the subduction rate at the just-right level that advanced life needs means that the sliding friction between crustal plates at the subduction zones must be maintained at just-right levels. Also, the crustal slabs undergoing subduction need to bend at the just-right levels and rates. All this fine-tuning adds to the growing weight of evidence that a supernatural, super-intelligent Creator is necessary to explain all the characteristics of Earth that must be present in order for the planet to be habitable by advanced life. It also implies that, unless the Creator has intervened in other places in the cosmos, astronomers will not find advanced-life habitable planets elsewhere in the Milky Way Galaxy or in any other galaxy.

1. Norman Sleep, “Tectonics and Habitability of Super-Earths,” Astrobiology 8 (April 2008): 395.

Subjects: Geology and the Bible, Geophysical Design, Plate Tectonics

Earth Just Barely Large Enough

February 13th, 2008

By Dr. Jeff Zweerink

All the recent talk about global warming highlights one critical characteristic of Earth that makes the planet habitable, namely plate tectonics.

As I discussed two weeks ago, Venus and Earth are remarkably similar in terms of their size and composition. Both probably started out with large oceans of water. While Earth continues to maintain a global temperature that supports a vital stable water cycle, the surface of Venus is bone dry with temperatures near 800oF.

Unlike on Venus, Earth’s plate tectonics still operate and therefore perform the important function of removing greenhouse gases from Earth’s atmosphere. Without plate tectonics, a dense life-suffocating carbon dioxide atmosphere would surround Earth.

Research presented at the 211th meeting of the American Astronomical Society (AAS) puts tight constraints on how large a planet must be to sustain long-standing plate tectonics. Essentially, all rocky planets larger than twice the size of Earth will experience plate tectonics. However, as a consequence of thinner tectonic plates and greater geological stresses these “super-Earths” would experience more vigorous plate tectonics.

Furthermore, the research illuminates two limits for habitable, tectonically active planets. First, any planet larger than ten times Earth’s mass will attract a dense hydrogen and helium atmosphere, like the gas giants in our solar system. Consequently these planets cannot be habitable. On the other end of the spectrum, Earth is barely large enough to sustain plate tectonics. Earth’s large, liquid water oceans and abundant interior water both lubricate tectonic movements and give Earth’s interior the necessary characteristics to support tectonic activity. Thus, for any planet closer to Earth’s mass, the planet must exhibit the facilitating properties of water.

This research implies that scientists will discover more potentially habitable planets. However, the tectonic activity on these super-Earths will be far more destructive than on Earth. Thus, RTB’s creation model predicts that planets much larger than Earth will prove uninhabitable—or at least incapable of supporting human life.

Subjects: Big Bang, Earth/Moon Design, Multiverse

EXTRA! EXTRA! READ ALL ABOUT IT!

July 1st, 2007

By Dr. Jeff Zweerink

You’re Standing on a Floating Plate This just in—ice floats in water! Unlike most materials, as liquid water cools to near its freezing point, its density decreases and then expands as it freezes. Thus, colder water and any ice float on the warmer liquid water below.

Seems anticlimactic, doesn’t it? However, if water did not possess this unusual property, Earth’s habitability would dramatically decrease. Ponds, lakes, streams, rivers, and possibly even oceans would freeze completely solid—not just on the surface—more regularly and take far longer to thaw after temperatures rise.

Amazingly, a similar phenomenon occurring deeper in the Earth may be responsible for enabling our planet to maintain the long-standing plate tectonics so critical for enduring life. Recall that Earth consists of a shallow crust, mantle, and an outer and inner core. Moving from the crust toward the core, most of the relevant materials in Earth’s interior absorb water more readily (because both temperature and pressure increase with depth). One material, a mineral called aluminous orthopyroxene found throughout the Earth, exhibits peculiar behavior in the upper mantle (just below the crust) called the asthenosphere. In this region, aluminous orthopyroxene’s capacity to dissolve water drops dramatically, but increases again at greater depths. Therefore, the materials in this region of the mantle absorb less water than those above and below with the consequence that a large abundance of “hydrous” melt exists in the asthenosphere. Think of a cracker sandwich with jelly (as the asthenosphere) in the middle.