Today’s New Reason To Believe

Posted by Fazale ‘Fuz’ Rana, Ph.D.

New Discovery Undercuts Origin of Life at Hydrothermal Vents

Most people now recognize that smoking takes years off of one’s life. But if it wasn’t for smokers, life’s start wouldn’t be possible—at least according to some origin-of-life researchers.

One prominent origin-of-life model posits life’s beginnings at deep-sea hydrothermal vents, sometimes referred to as “black smokers.” These structures result when superheated water pushes through the Earth’s crust on the ocean floor to form a sea vent. The water that spews out of the vent is rich in dissolved minerals including sulfides. When the superheated water comes into contact with cold water surrounding the sea vent, it causes the metal sulfides to precipitate. These precipitates look like black smoke emanating from the sea floor. Over time as the sulfides deposit around the vent, a chimney-like structure forms.

A complex, rich ecosystem is associated with black smokers. Some bacteria and archaea thrive near hydrothermal vents. Here the microbes make use of gases like methane and the sulfides through a process called chemosynthesis to generate foodstuff. These chemoautotrophs serve as the primary producers in the hydrothermal vent communities.

Since the discovery of thriving microbial communities near underwater smokestacks, origin-of-life researchers have thought that perhaps life began in similar locales on early Earth. If life can live at hydrothermal vents today, why couldn’t it originate there as well? After all, the microbes thought to be representatives of some of the oldest organisms on Earth are hyperthermophiles and thermophiles, the types of (heat-loving) organisms found at these vents. Additionally, laboratory simulation experiments designed to mimic the chemical and physical conditions of hydrothermal vents have demonstrated that biologically interesting compounds could have been generated in these locales on early Earth. Presumably, these compounds could have formed a complex chemical mix that eventually spawned the first life-forms.

New research, however, indicates that this explanation for the origin of life is probably not correct.

This work took advantage of the typical biochemical makeup of nucleic acids, like DNA and RNA, and proteins of hyperthermophiles and thermophiles to determine (from an evolutionary standpoint) the identity of the last universal common ancestor.

The composition of these important biomolecules serves as a “molecular thermometer” of sorts. For example, hyperthermophiles and thermophiles possess nucleic acids more enriched in guanine and cytosine compared to those of organisms that live at more moderate temperatures. Likewise, the amino acid compositions of thermophilic proteins are depleted within certain amino acids. (For a detailed discussion of the principles behind this analysis go here.)

Using both thermometers, the researchers concluded that the last universal common ancestor must have lived at moderate temperatures. That is, it wasn’t thermophilic. This means that from an evolutionary vantage point, life’s origin probably didn’t take place at hydrothermal vents. (For more information on other problems associated with alternative origin-of-life explanations see Origins of Life.)

It looks like smoking wasn’t all that good for Earth’s first life either.

Previously Posted on October 26th, 2007 by David H. Rogstad, Ph.D.

When the Bible tell us that we have been made from the “dust of the earth,” and will eventually “return to the dust,” it is more true than perhaps the authors realized. Prevailing theory for the formation of planets maintains that they form when dust particles in the disk of material rotating around a central star begin to stick together in clumps (just like the dust under my bed!). Gradually they grow in size, from particles the size of sand, to pebbles, rocks, and eventually boulders as big as a meter across. Next, these boulder-sized objects aggregate into objects called planetesimals that can be many kilometers across. Finally, gravity takes over and draws these planetesimals together to form planets.

Scientists have accounted for most of the physical processes necessary to bring about the accumulation of material to finally form planets, except for that one step of going from boulders to planetesimals. On occasion it has been called one of the major unsolved problems in planet formation, and has often been the focus of dispute by some in the young-earth creationist community as grounds for rejecting this explanation for how solar systems like our own were formed.

New research could help resolve the issue. In a paper published in the August 30, 2007 issue of Nature, Anders Johansen and several of his colleagues describe a set of simulations that, to their knowledge, for the first time permits accurate and complete modeling of how these objects go from meter-sized boulders to kilometer-scale planetesimals.

The team needed to solve two major problems: (1) boulders are not expected to stick together very easily because of the weakness of their gravitational interaction, and (2) the time to interact is short because the objects tend to spiral into the central star in only a few tens of orbits, due to the “headwind” from slower rotating gas.

The results of their simulations demonstrate, however, that boulders can, indeed, collapse together under the force of gravity. What they show is that some regions in the disk randomly undergo local increases in the density of boulders. Then gravity can act over a long-enough period of time and with sufficient strength to build up larger bodies.

While the authors are cautious about claiming to have resolved all the difficulties, they do offer a possible path for filling this gap in planet formation. Once again, more detailed studies have yielded an explanation for a particular phenomenon that at first had been criticized.

Certainly there are areas of science where the lack of an explanation is grounds for abandoning a theory, but this is not one of them. Instead, to (the planetary) dust we shall return.

Previously Posted on October 26th, 2007 by David H. Rogstad, Ph.D.

When the Bible tell us that we have been made from the “dust of the earth,” and will eventually “return to the dust,” it is more true than perhaps the authors realized.

Prevailing theory for the formation of planets maintains that they form when dust particles in the disk of material rotating around a central star begin to stick together in clumps (just like the dust under my bed!). Gradually they grow in size, from particles the size of sand, to pebbles, rocks, and eventually boulders as big as a meter across. Next, these boulder-sized objects aggregate into objects called planetesimals that can be many kilometers across. Finally, gravity takes over and draws these planetesimals together to form planets.

Scientists have accounted for most of the physical processes necessary to bring about the accumulation of material to finally form planets, except for that one step of going from boulders to planetesimals. On occasion it has been called one of the major unsolved problems in planet formation, and has often been the focus of dispute by some in the young-earth creationist community as grounds for rejecting this explanation for how solar systems like our own were formed.

New research could help resolve the issue. In a paper published in the August 30, 2007 issue of Nature, Anders Johansen and several of his colleagues describe a set of simulations that, to their knowledge, for the first time permits accurate and complete modeling of how these objects go from meter-sized boulders to kilometer-scale planetesimals.

The team needed to solve two major problems: (1) boulders are not expected to stick together very easily because of the weakness of their gravitational interaction, and (2) the time to interact is short because the objects tend to spiral into the central star in only a few tens of orbits, due to the “headwind” from slower rotating gas.

The results of their simulations demonstrate, however, that boulders can, indeed, collapse together under the force of gravity. What they show is that some regions in the disk randomly undergo local increases in the density of boulders. Then gravity can act over a long-enough period of time and with sufficient strength to build up larger bodies.

While the authors are cautious about claiming to have resolved all the difficulties, they do offer a possible path for filling this gap in planet formation. Once again, more detailed studies have yielded an explanation for a particular phenomenon that at first had been criticized.

Certainly there are areas of science where the lack of an explanation is grounds for abandoning a theory, but this is not one of them. Instead, to (the planetary) dust we shall return.