Darwin's pond, revisited

Darwin’s “warm little pond” scenario for the origin of life on earth may not have been hot enough to do the work of chemosynthesis, combining the elements of life—CO2, methane, and water—into more complex biological compounds, and some researchers suggest that hydrothermal vents like those found today in abyssal ocean depths are a more likely candidate for the environment in which life first evolved.

Water gushing from hydrothermal events tends to be alkaline from reaction with minerals in the earth’s crust. When an alkaline hydrothermal fluid (that is, a fluid with low Hydrogen ion levels) mixes with acidic seawater (which has a higher H ion concentration), the resulting pH gradient creates potential energy that can be used to power chemical reactions by the diffusion of hydrogen ions in a process called chemiosmosis.

The oldest and simplest forms of life on Earth may have used chemiosomosis as an energy source.

Source: Nicole Branan writing in Earth, May 2010, based on research by Wm Martin and others in BioEssays

At the beginning

To put the Earth’s history in context, our planet and our solar system formed about 4 and a half billion years ago, in a Universe that had its beginning at least 13 billion years ago.

In this beginning there was a tremendous expansion of all matter and energy in the Universe, in an event that astronomers call the Big Bang. From this event the first elementary particles such as quarks formed; after several hundred million years atoms, and elements such as hydrogen and helium formed, eventually, after a 100 million years, these elements condensed and formed the first stars.

Perhaps a billion years after the Big Bang galaxies began to form, including our own Milky Way Galaxy.

To be continued...

Links for more information on the Big Bang from the University of Michigan and NASA.

Big Bang timeline (illustration, above) from here.

Big numbers. Really. Big.

This week GeoLog will begin a trip through time, exploring the physical and biological changes on Earth through the more than four-and-a-half billion years of its history, as told through the rocks and fossils that are the physical evidence of these changes. But first, a few words about our frame of reference:

Geologists tend to use numbers like 4.6 billion without a second thought. In fact, the scope of what we call geologic time is ENORMOUS and extremely hard to comprehend, especially for those of us who spend our days counting seconds, minutes and hours.

After all, our own life spans are on the order of 10s to one hundred years; known civilization goes back only thousands of years, and there were no modern humans around millions of years ago.

Our ability to comprehend the vast eras of geologic time is severely challenged by the remoteness and scope of these events.

Links for some help in visualizing these large numbers:

This site measures millions and billions in pennies, and the image of one billion pennies (above) is from here.

Teachers can find an exercise for class use on big numbers here, and the geologic time scale here and here.