The microbes that loved the sun; some very tiny organisms living millions of years ago recorded the heavenly interaction among some very large bodies: the earth, the sun and the moon.
The Microbes That Loved the Sun
Among the larger species of plants and animals Plants and Animals are a Canadian indie-rock band from Montreal, comprised of guitarist-vocalists Warren Spicer and Nic Basque, and drummer-vocalist Matthew Woodley. They are signed to Secret City Records. , it's easy to spot those individuals that worship the sun. Every winter, for example, New Yorkers can be seen flocking to Florida, where they follow the sun's every move. And a houseplant houseplant
Plant adapted for growing indoors, commonly a member of a species that flourishes naturally only in warm climates. Two factors contribute to the success of the huge number of species grown as houseplants: they must be easy to care for, and they must be able to turned away from the window in the morning will most assuredly be found bending back toward the luxuriant luxuriant /lux·u·ri·ant/ (lug-zhoor´e-ant) growing freely or excessively. rays in the afternoon.
But homing in on the really devout solar trackers among much smaller organisms is not always an easy task. In order to find evidence of movement toward the sun in groups of photosynthetic microorganisms such as blue-green algae blue-green algae, popular name for those microorganisms that are now more properly called cyanobacteria. , Stanley M. Awramik and James Vanyo had to get on their hands and knees in shallow-water pools and tidal flats. They peered intently at the orientation of th e centimeter-high stromatolites--columns or tufts constructed by sticky mats of these microorganisms as they trap passing sediments and cement them into layers.
As the two University of California The University of California has a combined student body of more than 191,000 students, over 1,340,000 living alumni, and a combined systemwide and campus endowment of just over $7.3 billion (8th largest in the United States). at Santa Barbara Santa Barbara (săn'tə bär`brə, –bərə), city (1990 pop. 85,571), seat of Santa Barbara co., S Calif., on the Pacific Ocean; inc. 1850. scientists report in upcoming issues of SCIENCE and EOS Eos (ē`ŏs), in Greek religion and mythology, goddess of dawn; daughter of the Titans Hyperion and Theia. Every morning she arose early and preceded her brother Helios into the heavens. , they discovered a number of stromatolites tilting toward the sun and not, like most of their neighbors, in the direction of sediment-rich current flow. This is the first report of heliotropism--the inclination of a structure toward the average direction of sunlight -- in stromatolites being formed today, says Vanyo.
The finding of heliotropism he·li·ot·ro·pism
Growth or orientation of a sessile organism, especially a plant, toward or away from the light of the sun.
he in modern stromatolites not only sheds light on the behavior of living microorganisms but also helps to confirm an earlier geologic theory linking the tiny architectures of ancient stromatolites to the much larger dynamics of the ancient solar system solar system, the sun and the surrounding planets, natural satellites, dwarf planets, asteroids, meteoroids, and comets that are bound by its gravity. The sun is by far the most massive part of the solar system, containing almost 99.9% of the system's total mass. .
According to the researchers, most of the scientific thinking about the interaction between the earth, sun and moon comes from the last few thousand years of historical records of observations and from studies of distant stars, from which scientists can glean something about the beginnings of our own system 5 billion years ago. But for the several billions of years in between the system's beginnings and the recent past, there is little direct information; theoretical models are needed to estimate, for example, how the gravitational grav·i·ta·tion
a. The natural phenomenon of attraction between physical objects with mass or energy.
b. The act or process of moving under the influence of this attraction.
2. tug of the moon has slowed the rotation of the earth, causing the number of days per year to decline with time.
Because organisms are sensitive to such things as the amount and direction of sunlight, researchers like Awramik, a paleobiologist, and Vanyo, an astronomer and engineer, have turned to the fossil record on earth for traces of earth-moon-sun dynamics. Some scientists have used the growth rings of ancient corals, for instance, to estimate periods such as the number of days that made up a year in the distant past. However, fossils of corals and other invertebrates date back only to the Cambrian period, about 570 million years ago. Stromatolites, on the other hand, extend back in the fossil record to 3.5 billion years ago--almost as old as the earth itself.
But the use of stromatolites as paleontological pa·le·on·tol·o·gy
The study of the forms of life existing in prehistoric or geologic times, as represented by the fossils of plants, animals, and other organisms. clocks has not been straightforward. A few researchers have suggested that the sediment layers, or laminae, in fossil stromatolites could be used to estimate past lunar and annual periods; others have proposed that the tilt of a stromatolite stromatolite
Layered deposit, mainly of limestone, formed by the growth of blue-green algae (see cyanobacteria). These structures are usually characterized by thin, alternating light and dark layers that may be flat, hummocky, or dome-shaped. column could be used to deduce the latitude of the structure when it was formed. However, these suggestions were discredited, say Awramik and Vanyo, by studies showing that stromatolite patterns were often driven by the patterns of current flow and not by the orientation of the sun relative to the earth.
More recently, Awramik and Vanyo came across some stromatolites with growth patterns that could not easily be attributed to current flow. The Anabaria juvensis stromatolites, taken from the Bitter Springs formation in central Australia, snaked upward in the 850-million-year-old fossil record in the distinct pattern of sine waves.
The researchers proposed that the microorganisms that made the stromatolites produced a new lamina LAMINA - A concurrent object-oriented language.
["Experiments with a Knowledge-based System on a Multiprocessor", Third Intl Conf Supercomputing Proc, 1988]. each day by binding sediments and then working their way up toward the top of the new lamina to get the most of the sun's rays. The sinusoidal sinusoidal /si·nus·oi·dal/ (si?nu-soi´dal)
1. located in a sinusoid or affecting the circulation in the region of a sinusoid.
2. shaped like or pertaining to a sine wave. pattern resulted, they argued, becuase the microorganisms were building toward the sun, which, from the microorganisms' point of view, moved in the sky with the change in season. To microorganisms sitting just north of the equator, the sun would move toward the south during the winter and toward the north in the summer.
By counting the number of laminae in one cycle of a sine wave, Awramik and Vanyo estimate there were 435 days per year during the late Proterozoic. "Our results agree well both with estimates extrapolated from the paleozoic [570 million to 245 million years ago] fossil invertebrate invertebrate (ĭn'vûr`təbrət, –brāt'), any animal lacking a backbone. The invertebrates include the tunicates and lancelets of phylum Chordata, as well as all animal phyla other than Chordata. data and with the theoretical estimates using geophysics," says Awramik.
In addition to the number of days in a year, the sine wave pattern of the ancient stromatolites contains information about another important astronomical parameter called the obliquity of the ecliptic obliquity of the ecliptic: see inclination. , or the angle between the planes of the earth's equator and the planet's orbit around the sun. Scientists think this angle might have been decreasing over time, but studies estimating values for this angle in the past have produced differing results. By measuring the maximum angle at which the sine wave deviates from the average direction of the column, Awramik and Vanyo obtained a value of 26 degrees 30 minutes.
The researchers also were able to estimate the angle of th earth's magnetic field Earth's magnetic field (and the surface magnetic field) is approximately a magnetic dipole, with one pole near the north pole (see Magnetic North Pole) and the other near the geographic south pole (see Magnetic South Pole). with respect to its spin axis during the late Proterozoic. They did this by looking at paleomagnetic studies of the rocks to determine the direction of the past field, and by using the plane along which the stromatolitic sine waves grew to define the past north-south plane of the earth and its spin axis. "The value we got indicates that at least back 850 million years ago the magnetic pole closely approximated the axis of rotation Noun 1. axis of rotation - the center around which something rotates
mechanism - device consisting of a piece of machinery; has moving parts that perform some function -- something that was just assumed in geophysical studies," says Awramik.
In order for Awramik and Vanyo to extract astronomical information from the fossil patterns of stromatolites they had to assume, among other things, that the microorganisms lived near the equator and that they produced laminae each day. But the most important assumption was that stromatolite growth was heliotropic he·li·ot·ro·pism
Growth or orientation of a sessile organism, especially a plant, toward or away from the light of the sun.
he . And on this point the researchers were on shaky ground, because no modern examples of heliotropism in stromatolites had ever been reported.
So the researchers went on a heliotropism hunt. Vanyo and Rick hutchinson, a research geologist at Yellowstone National Park Yellowstone National Park, 2,219,791 acres (899,015 hectares), the world's first national park (est. 1872), NW Wyo., extending into Montana and Idaho. It lies mainly on a broad plateau in the Rocky Mts., on the Continental Divide, c. , looked in the thermal effluents from geysers The examples and perspective in this USA may not represent a worldwide view of the subject.
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This is an alphabetical list of notable geysers, a type of erupting hot spring:
Awramik, searching in the highly saline Hamelin Pool in Shark Bay, western Australia, met with success as well. At two sites exposed to the tides, he found small tufts inclined to the north, the general direction of the sun as seen from the southern hemisphere. The tufts were not leaning in either the east-west direction of the tidal currents or the general direction of the winds from the south. He also discovered dozens of much larger stromatolite columns in an area permanently submerged below the water's surface. These columns were tilted toward the north; ripples in the sandy bottom again showed that the current moved in a east-west direction. Awramik says that most recently he's also found evidence for heliotropism in millimeter-sized stromatolite tufts in the Caribbean.
"We're not saying that [heliotropism] is a common phenomenon in either ancient or modern stromatolites, but it's probably more common than people previously thought," observed Awramik. Vanyo adds that only a few sinusoidal patterns have been found in the stromatolite fossil record, in part because people have not looked for them. "The cost and effort of digging up these things and then cutting the rocks in the correct way to expose the sine waves is huge," he says.
As for modern stromatolites, the researchers are not sure why some structures are heliotropic while others in the same region are not. The architecture of a stromatolite depends on a mosaic of different factors, including temperature, water chemistry, sediment flow and other organisms in addition to sunlight, they say. Heliotropism occurs when the influence of these other factors is suppressed in some way. The effects of competing organisms, for example, might be damped in both the Yellowstone National Park and Shark Bay areas, says Awramik, because these environments are stressed by either high water temperatures or salinity, which discourage other species from settling there. The researchers plan to conduct laboratory experiments this year to better understand what controls the blueprint of stromatolite growth.