Scientists Strengthen Case for Life on Earth More Than 3.8 Billion Years Ago

Ten years ago, an international team of scientists reported evidence, in a controversial cover story in the journal Nature, that life on Earth began more than 3.8 billion years ago—400 million years earlier than previously thought. A UCLA professor who was not part of that team and two of the original authors will report in late July that the evidence is stronger than ever.

Craig E. Manning, lead author of the new study and a professor of geology and geochemistry in the UCLA Department of Earth and Space Sciences, painstakingly mapped an area on Akilia

Island in West Greenland where ancient rocks were discovered that may preserve carbon-isotope evidence for life at the time of their formation. Manning and his co-authors—T. Mark Harrison, a UCLA professor of geochemistry, director of UCLA's Institute of Geophysics and Planetary Physics, and University Professor at the Australian National University; and Stephen J. Mojzsis, assistant professor of geological sciences at the University of Colorado, Boulder—conducted new geologic and geochemical analysis on these rocks. Their findings will be reported in the new issue of the American Journal of Science. Harrison and Mojzsis were co-authors on the Nov. 7, 1996, study in Nature.

"This paper shows, with far greater confidence than we ever had before, that these rocks are older than 3.8 billion years," said Manning, who has conducted extensive research in Greenland. "We have shown that the rocks are appropriate for hosting life.

"Everything from the basic geology to the analysis in the original report (in Nature) has been challenged," said Manning, who has expertise in areas that have become central to the debate, including the chemistry of water and the interaction of water and rock. "The chemical evidence for life has been challenged, as have been the minerals to determine whether life was present, whether the rocks have the origin that was originally attributed to them, and whether the rocks were as old as originally envisioned. We didn't go to Greenland in response to the criticism. We went to learn the age of the rocks and to make a better geologic map of the area than any that existed."

At the time of the 1996 Nature paper, there was no reliable map showing the geology of the area, Manning said. So he created one.

"I wandered around that outcrop for two-and-a-half weeks—it's not a big area—with a clipboard, maps, a compass and grid paper. We mapped it like an archeologist would map it," Manning said. "It became clear that these rocks that hosted life line up into two beautiful, coherent layers. They are not randomly distributed, as you might expect if the alternative interpretation is right. I'm very confident about that. I went to Greenland with some skepticism, but I became more and more confident as time went on that the original interpretation was right."

"It could have gone any way," Harrison said. "We could have placed the claim on much firmer footing, or we could have proved ourselves wrong. We found a much more compelling cross-cutting relationship in the rocks than we originally thought."

"We've been holding our fire rather than fire away at each criticism in a piecemeal way," he said. "We've gone back to Greenland and done the study from the ground up, with much more data than existed at the time of the original paper. I'm much more confident today than I was in 1996 about the likelihood that this is evidence of early life. This is not 'smoking gun' evidence—we are not seeing fossils—but in every case, the model has come through with flying colors."

Manning agrees, saying he is confident the rocks contain evidence of ancient life, but "it's not a slam dunk."

Why is there doubt? After more than 3.8 billion years, the rocks are severely damaged.

"They have been folded, distorted, heated and compressed so much that their minerals are very different from what they were originally," Harrison said.

"Akilia Island was not the best place to search for evidence of early life; it's simply the place where it turned up," Harrison said.

"There's nothing special about Akilia Island," Manning said. "If life was there, it should have been abundant on Earth 3.83 billion years ago. The only place where that's been tested so far, also in Greenland, has come up positive."

One of the key methods for dating the rocks is by carefully analyzing cross-cutting intrusions made by igneous rocks, Manning said, adding, "Whatever is cross-cut must be older than that which is doing the cross-cutting. We went there to find these cross-cutting relationships, which we did."

The research on the Akilia rocks is federally funded by the National Science Foundation (http://www.nsf.gov/) and the NASA Astrobiology Institute (http://nai.arc.nasa.gov/), a partnership between NASA, 12 major U.S. teams and six international consortia.

Scientists look for evidence of life in ancient rocks like those from Akilia Island by searching for chemical suggestions and isotopic evidence. The very strong isotopic evidence for ancient life found in the 1996 study included a high ratio of one form of carbon—an isotope—to another, which provides a "signature of life," Mojzsis said.

The carbon aggregates in the rocks have a ratio of about 100-to-one of 12C (the most common isotope form of carbon, containing six protons and six neutrons) to 13C (a rarer isotopic form of carbon, containing six protons and seven neutrons). The light carbon, 12C, is more than 3 percent more abundant than scientists would expect to find if life were not present, and 3 percent is very significant, Harrison said.

Carbon inclusions in the rocks were analyzed with UCLA's high-resolution ion microprobe—an instrument that enables scientists to learn the exact composition of samples. The microprobe shoots a beam of ions, or charged atoms, at a sample, releasing from the sample its own ions, which are then analyzed in a mass spectrometer. Scientists can aim the beam of ions at specific microscopic areas of a sample and analyze them.

While critics noted there are ways to make light carbon in the absence of life, Harrison considers those possibilities to be "extremely unlikely," especially in light of another discovery of rocks in Western Greenland, not far away, of the same age, and a similar ratio of 12C to 13C.

The scientists see light carbon inclusions in a phosphate mineral called apatite, which is also the material of which bones and teeth are made.

The form of life the researchers believe they have discovered was probably a simple microorganism, although its actual shape or nature cannot be ascertained, Mojzsis said, because heat and pressure over time have destroyed any original physical structure of the organisms.

Harrison said of UCLA's ion microprobe and the research: "The individual samples are very small, and no other instrument would have been sensitive enough to reveal precisely the isotopic composition and location of the carbon inclusions in the rock."

It is unknown when life first appeared on Earth, which is approximately 4.5 billion years old.

The residue of ancient life that the scientists believe they have found existed prior to the end of the "late heavy bombardment" of the Moon by large objects, a period which ended approximately 3.8 billion years ago, Harrison noted.

"Life is tenacious, and it completely permeates the surface layer of the planet," Mojzsis said. "We find life beneath the deepest ocean, on the highest mountain, in the driest desert and the coldest glacier, and deep down in the crustal rocks and sediments."

An unanswered question is how life originally could have arisen from lifeless molecules and evolved into the already sophisticated isotope fractioning life forms recorded in the Akilia rocks.

The American Journal of Science is the oldest scientific journal in the United States that has been published continuously, dating back to the 19th century. While the journal is being published in late July, it will carry a date of May 2006.

California's largest university, UCLA enrolls approximately 38,000 students per year and offers degrees from the UCLA College of Letters and Science and 11 professional schools in dozens of varied disciplines. UCLA consistently ranks among the top five universities and colleges nationally in total research-and-development spending, receiving more than $820 million a year in competitively awarded federal and state grants and contracts. For every $1 state taxpayers invest in UCLA, the university generates almost $9 in economic activity, resulting in an annual $6 billion economic impact on the Greater Los Angeles region. The university's health care network treats 450,000 patients per year. UCLA employs more than 27,000 faculty and staff, has more than 350,000 living alumni and has been home to five Nobel Prize recipients.

WHAT IS GRANITE?—Granite is a hard crystalline rock that tends to be light-colored. Its crystals are large enough that you can easily see them. It is a mixture of very light quartz and feldspar crystals, along with some darker crystals which are usually mica and hornblende. The individual crystals in most granite are a fraction of an inch to about half an inch wide:

Granite is very solid and hard because it tends to have no cracks or seams in it. This is why it is quarried and used in building bridges and buildings. Because, unlike many other rocks, it does not tend to crack, granite can support immense weights—as much as 15,000 to 20,000 pounds per square inch (6,804 to 9,072 kg per square 2.54 cm]. This lack of cracking and crumbling, makes it invaluable for monuments and statues. There are few rocks as solid as granite.

Four special facts need to be mentioned here:

(1) Rhyolite is chemically like granite, but it has much smaller crystals. We will later learn that granite, when melted by men, never hardens again into granite, but only into rhyolite! It is impossible for anyone, using any kind of technique, to make granite out of melted-down granite! As we shall discover, this is because granite was originally made in solid form. It cannot be produced from melted materials, and all attempts to do so fail.

(2) A rock that is similar to granite is gneiss (pronounced nice). The feldspar and quartz crystals in gneiss form thin layers between which mica crystals often lie in wavy bands. A similar rock is schist, in which the layers are thicker, more plate-like, and more horizontal than gneiss.

(3) Porphyry (POR-fih-rih) is the name of any igneous rock in which one kind of crystal is much larger than the rest. When a granite has large crystals of feldspar (one to several inches long), it is called granite porphyry. But it is still granite. (The mass of smaller crystals in which the larger ones lie is called the "groundmass.")

(4) Granite never contains fossils. This is very important, for it could not be one of the original rocks of the earth if it contained fossils.

Even evolutionary geologists are puzzled over the fact that granite and certain other rocks cannot be formed today.

"We find certain rock types in the geologic column that are not being seen to form . . anywhere on earth today. Where can granite be observed forming? . . Herz attributes the formation of anorthosite to . . possibly a great cataclysm . . It is possible that other rock types were created during and following catastrophic events on earth."—*Edgar B. Heylmun, "Should We Teach Uniformitarianism?" in Journal of Geological Education, Vol. 19, January 1971, p. 38.

WHY GRANITE IS SO IMPORTANT—If you want to build a house, you erect all the materials on a very solid foundation. If you do not do so, the ground beneath ma y eventually sink different amounts in different places, and the house will crack and may eventually collapse. All of our continents have been placed on a very solid foundation: granite. There is no rock more solid and enduring than granite. There are immense quantities of it beneath us.

Robert Gentry's research establishes the fact that all of this granite came into existence in solid form within less than 3 minutes time. Yet if this is so, then all the rest of the world had to be brought Into existence just as rapidly. If the granite suddenly appeared in less than 3 minutes, while the rest of the world was molten rock, then the granite would have melted. So our world came into existence all at once—and all of its rock and mineral matter within 3 minutes.

HOW THICK IS THIS GRANITE?—This is an important question. According to standard geological theory, below some sedimentary strata, the granite begins and continues on a great distance, finally stopping at a point where seismic explosion tests reveal that the underground "radar" bounces off at a somewhat different angle. That point, called the "Conrad Discontinuity," averages about 7 km [4.35 mi.] below the surface of the continents. For many years it has been theorized that the granite goes down to about that distance and then, at the Conrad discontinuity, stops, and basalt begins.

The surprising discovery, made only recently, is that below the Conrad discontinuity,—the granite continues on uninterrupted) At the present time we have no idea how deep the granite may go. We already know it to continue down 4.5 km [2.7 mi.] past the Conrad line; perhaps it may continue on to the 20 mile [32 km] depth, where the Mohorovicic discontinuity occurs! Because the Conrad discontinuity has been so deeply penetrated, scientists now have absolutely no idea how deep that granite may extend below us. Yet Gentry's research shows that all that granite came into existence in solid form within less than 3 minutes.

"In the world of deep drilling, the Soviet Union stands far ahead of all other nations. Its current program features 11 deep-hole projects, including the deepest drill-hole in the world. Located on the Kola peninsula near Scandinavia, this granddaddy hole is 19 years old and presently reaches a depth of 12.066 kilometers [7.497 miles]. The Soviets will soon resume drilling at Kola, aiming for a depth of 14 to 15 km [8.699 to 9.32 mi.] ..

"Kola revealed how far from truth scientific theory can roam. Before drilling, the Soviet scientists performed seismic profiles and found several clear reflectors. One of the strongest sets fell at a depth between 7.5 and 8.5 km[4.66 and 5.28 mi.], where there was a sharp contrast in the seismic velocity of the rocks above and below the reflectors. This contrast, found on all continents, is called the Conrad discontinuity, and it supposedly represents the boundary between the middle and lower portions of the crust.

"According to theory, the crust resembles a layer cake, with sedimentary rock layers on top, acidic granite-type rocks in the middle, and thick sheets of basaltic rocks on the bottom. Since no one had ever drilled through the Conrad discontinuity to test this idea, the Soviet scientists relished the possibility of piercing the deep basalt region.

"Yet when the drill actually reached a depth of 7.5 km (4.66 mi.], the scientists did not find basaltic rock. Even at the present depth of 12 km [7.456 mi.], the drill has not crossed into the region of layered basaltic rock. The Soviets now believe that if the basalt layers exist, they must lie much deeper.

"That leaves open a question: What do the strong 7.5-km [4.86 mi.]-deep reflectors represent? Although theories abound, nobody quite knows, according to Vernik. Drilling showed that the reflectors don't represent any physical structure, such as a fault or a boundary."—*Richard Monastersky, "Inner Space," in Science News, October 21, 1989, pp. 138. 267. [Italics ours.]

2 - HALOS IN THE GRANITE

HALOS IN THE GRANITE—In order to better understand a rock, you need to look at it through a microscope. In the late 1800s, scientists began studying rocks with microscopes in order to better understand their crystals and composition. Learning how to cut rocks into thin slices, they turned their microscopes on certain rocks, especially granite,—and found small colored concentric circles inside them. What made those small circles?

This was the beginning of a line of research that resulted in the astonishing discovery described in this study.

When cut exactly through the middle, there would be a small grain in the very center, along with one or more circles around it. (To avoid confusion, in this report we shall always name that central dot the "grain," although it is actually a radioactive particle.) But when sliced just above or below this central slice, the grain in the middle would be missing and the circles would be smaller. This slicing proved that these were not circles, but spherical shells, that were around each central grain. These circles (actually sections of spheres) were given the name "halos."

SAYING IT AGAIN—When thin, translucent slices of certain minerals were examined under high magnification, some of them were discovered to have tiny dots imbedded in them. Surrounding these dots were concentric, colored rings. Each set of rings was actually a section (a slice) through a series of spherical shells, similar to when you slice through the many concentric circles inside an onion. The rings encircled the tiny grain in the center. That central grain was itself an entirely different mineral than the rock it was in.

COLORED CIRCLES—Although very tiny, these halos could be seen because they were of darker and different colors than the background mineral they were etched upon. (Color variation in minerals is called pleochroic, and so, because of their colors and shape, they were initially named "pleochroic (PLAY-oh-crow-ik) halos," but scientists today generally call them "radio halos," for reasons soon to be explained.

It was obvious that the small grain in the center was probably the solution to the mystery of the halo, but what was it? Then, about the beginning of our century, uranium and other elements were discovered to be radioactive.

WHAT IS RADIOACTIVITY?—All matter is made of atoms. At the center of each atom is a nucleus. An oversimplification would be this: Flying around the nucleus are electrons with negative electrical charges. The nucleus itself is primarily made of protons (positively-charged units, about 2,000 times heavier than electrons), plus neutrons (same weight as the proton but electrically uncharged or neutral). Certain chemical elements (called radioactive elements) continually disintegrate and emit radiation from their nuclei. This radiation includes alpha, beta, and gamma rays, or particles.

(1)The alpha ray (alpha particle) is a small high-energy particle given off from the nuclei (cores) of radioactive atoms when they disintegrate. Each one has a positive charge and consists of two protons and two neutrons held together. Matter easily stops or absorbs most alpha rays. One or two sheets of paper will stop most alpha particles. (We will learn that beta particles are too weak to cause the radiohalos.)

(2) Beta rays (beta particles) are electrons from the nuclei of radioactive atoms as they disintegrate. Because of their high energy, beta particles can pass through solid matter several millimeters thick, or half an inch of wood. The energy of a beta particle is determined by the thickness of material it can penetrate. Some beta rays are ordinary negatively-charged electrons, but others are positive-charged ones, called positrons. (We will learn that it is the alpha particles which cause the radiohalos.)

(3) Gamma rays are the same as X-rays and have no charge. (Lacking a charge, they were found to have nothing to do with the halos.)

Halo coloration is first seen after 100 million alpha particles; it becomes darker after 500 million, and very dark after 1 billion.

"The reason why alpha particles develop halos, which electrons do not, is that heavy charged particles demonstrate a phenomenon known as the Bragg Peak, which is not demonstrated by light particles. The alpha particle is more than 7,000 times heavier than the electron, and has twice the electric charge of the opposite sign.

"This Bragg Peak results from a rapid loss of energy toward the end of the particle's path. Therefore, if a single alpha particle of sufficient energy were released at a point on the surface of a sheet of photographic film, a light linear smear with a dense spot toward the end of its path would be seen on the developed film. When several alpha particles are emitted in all directions from the same source, therefore, the dense spots form a ring. Hence the halos."—E. Theo Agard, Letter to the editors, Spectrum, April 1990, p. 45.

JOLY’S RESEARCH—In 1907, John Joly of Trinity College in Dublin, Ireland, began investigating these strange rock halos in granite. He found that the halos in the biotite (dark mica) were the easiest to work with. This was because the biotite could easily be split into thin slices,—and unless they were sliced he could not view them under a microscope.

By the time Joly began his work, scientists knew that uranium is the beginning (parent) of a long line, called a radioactive decay chain. Each of the successive daughter products is a member of that chain, and each of those members is called an isotope. .

WHAT IS THIS DECAY CHAIN?—As the U238 (uranium 238) begins to disintegrate it first ejects an alpha particle. But now, lacking that particle, that U-238 atom has become an atom of Th-234 (thorium 234). (Because the Th-234 came from the degeneration of U-238, scientists call it an "isotope" instead of an "atom;" it is an isotope of U-238.) That Th-234 isotope then loses a beta particle and becomes Pa-234 (protactinium 234). Thus, these radioactive atoms are capable of spontaneously changing, or decaying, to atoms of a different type.

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