Although researchers have determined the ages of rocks from other planetary bodies, the actual experiments—like analyzing meteorites and moon rocks—have always been done on Earth.
Now, for the first time, researchers have successfully determined the age of a Martian rock—with experiments performed on Mars. The work, led by geochemist Ken Farley of the California Institute of Technology Caltechcould not only help in understanding the geologic history of Mars but also aid in the search for evidence of ancient life on the planet. However, shortly before the rover left Earth inNASA's participating scientist program asked researchers from all over the world to submit new ideas When radiometric dating is done on a rock sample experiments that could be performed with the MSL's already-designed instruments.
Keck Foundation Professor of Geochemistry and one of the 29 selected participating scientists, submitted a proposal that outlined a set of techniques similar to those already used for dating rocks on Earth, to determine the age of rocks on Mars. Findings from the first such experiment on the Red Planet—published by Farley and coworkers this week in a collection of Curiosity papers in the journal Science Express —provide the first age determinations performed on another planet.
The paper is one of six appearing in the journal that reports results from the analysis of data and observations obtained during Curiosity's exploration at Yellowknife Bay—an expanse of bare bedrock in Gale Crater about meters from the rover's landing site. The smooth floor of Yellowknife Bay is made up of a fine-grained sedimentary rock, or mudstone, that researchers think was deposited on the bed of an ancient Martian lake.
In March, Curiosity drilled holes into the mudstone and collected powdered rock samples from two locations about three meters apart. Once the rock samples were drilled, Curiosity's robotic arm delivered the rock powder to the Sample Analysis on Mars SAM instrument, where it was used for a variety of chemical analyses, including the geochronology—or rock dating—techniques.
One technique, potassium-argon dating, determines the age of a rock sample by measuring how much argon gas it contains.
Over time, atoms of the radioactive form of potassium—an isotope called potassium—will decay within a rock to spontaneously form stable atoms of argon This decay occurs at a known rate, so by determining the amount of argon in a sample, researchers can calculate the sample's age. Although the potassium-argon method has been used to date rocks on Earth for many decades, these types of measurements require sophisticated lab equipment that could not easily be transported and used on another planet.
Farley had the idea of performing the experiment on Mars using the SAM instrument. There, the was heated to temperatures high enough that the gasses within the rock were released and could be analyzed by an onboard mass spectrometer. Farley and his colleagues determined the age of the mudstone to be about 3. Indeed, prior to Curiosity's geochronology experiment, researchers using the "crater counting" method had estimated the age of Gale Crater and its surroundings to be between 3.
Crater counting relies on the simple fact that planetary surfaces are repeatedly bombarded with objects that scar their surface with impact craters; a surface with many impact craters is presumed to be older than one with fewer craters.
Although this method is simple, it has large uncertainties. The researchers do, however, acknowledge that there is some uncertainty in their measurement. One reason is that mudstone is a sedimentary rock—formed in layers over a span of millions of years from material that eroded off of the crater walls—and thus the age of the sample drilled by Curiosity really represents the combined age of those bits and pieces.
So while the mudstone indicates the existence of an ancient lake—and a habitable environment some time in the planet's distant past—neither crater counting nor potassium-argon dating can directly determine exactly when this was. To provide an answer for how the geology of Yellowknife Bay has changed over time, Farley and his colleagues also designed an experiment using a method called surface exposure dating. Cosmic rays can only penetrate about two to three meters below the surface, so the abundance of cosmic-ray-debris isotopes in "When radiometric dating is done on a rock sample" indicates how long that rock has been on the surface.
Using the SAM mass spectrometer to measure the abundance of three isotopes that result from cosmic-ray bombardment—helium-3, neon, and argon—Farley and his colleagues calculated that the mudstone at Yellowknife Bay has been exposed at the surface for about 80 million years.
That is probably the most remarkable thing I've ever seen as a scientist, given the difficulty of the analyses," Farley says. This also helps researchers looking for evidence of past life on Mars. Cosmic rays are known to degrade the organic molecules that may be telltale fossils of ancient life. However, because the rock at Yellowknife Bay has only been exposed to cosmic rays for 80 million years—a relatively small sliver of geologic time—"the potential for organic preservation at the site where we drilled is better than many people had guessed," Farley says.
Furthermore, the "young" surface exposure offers insight into the erosion history of the site. The exposure of rock in Yellowknife Bay has been caused by wind erosion. Over time, as wind blows sand against the small cliffs, or scarps, that bound the Yellowknife outcrop, the scarps erode back, revealing new rock that previously was not exposed to cosmic rays.
At 80 million years ago, wind would have caused this scarp to migrate across the surface and the rock below the scarp would have gone from being buried—and safe from cosmic rays—to exposed," Farley explains.
Geologists have developed a relatively well-understood model, called the scarp retreat model, to explain how this type of environment evolves. Curiosity is now long gone from Yellowknife Bay, off to new drilling sites on the route to Mount Sharp When radiometric dating is done on a rock sample more dating can be done.
In another paper in the same issue of Science ExpressGrotzinger—who studies the history of Mars as a habitable environment—and colleagues examined the physical characteristics of the rock layers in and near Yellowknife Bay. They concluded that the environment was habitable less than 4 billion years ago, which is a relatively late point in the planet's history. His findings suggest that the surface water on Mars at that time would have been sufficient enough to make clays. Previously, such clays—evidence of a habitable environment—were thought to have washed in from older deposits.
Knowing that the clays could be produced later in locations with surface water can help researchers pin down the best areas at which to look for once habitable environments, he says. Farley's work is published in a paper titled "In-situ radiometric and exposure age dating of the Martian surface. Miller, and Edward Stolper.
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An image from the Curiosity rover's Front Hazard-Avoidance Camera shows the rover drilling into its second rock target, "Cumberland. First Papers from Curiosity. New Curiosity Papers Published. Written by Jessica Stoller-Conrad. When radiometric dating is done on a rock sample, the rock's age is determined. Log in for more information. Added days ago|9/29/ AM. Radiometric dating.
Geologists use radiometric dating to estimate how long ago rocks formed, and to infer the ages of fossils contained within those rocks. When radiometric dating is done on a rock sample, the rock s _____ is determined.
Why Dating Methods Can Date Nothing
Radiometric dating or radioactive dating is a technique used to date materials such as rocks or carbon , in which trace radioactive impurities were selectively incorporated when they were formed. The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay.
Together with stratigraphic principles , radiometric dating methods are used in geochronology to establish the geologic time scale. By allowing the establishment of geological timescales, it provides a significant source of information about the ages of fossils and the deduced rates of evolutionary change. Radiometric dating is also used to date archaeological materials, including ancient artifacts. Different methods of radiometric dating vary in the timescale over which they are accurate and the materials to which they can be applied.
All ordinary matter is made up of combinations of chemical elements , each with its own atomic number , indicating the number of protons in the atomic nucleus. Additionally, elements may exist in different isotopes , with each isotope of an element differing in the number of neutrons in the nucleus. A particular isotope of a particular element is called a nuclide. Some nuclides are inherently unstable.
That is, at some point in time, an atom of such a nuclide will undergo radioactive decay and spontaneously transform into a different nuclide. This transformation may be accomplished in a number of different ways, including alpha decay emission of alpha particles and beta decay electron emission, positron emission, or electron capture.
Although researchers make determined the ages of rocks from other planetary bodies, the actual experiments—like analyzing meteorites and moon rocks—have in any case been terminated on Soil. Now, after the fundamental time, researchers have successfully determined the age of a Martian rock—with experiments performed on Mars.
The work, led by geochemist Ken Farley of the California Begin of Technology Caltech Erudite, could not only relief in armistice the geologic history of Mars but also back in the search in behalf of evidence of ancient dash on the planet. Yet, shortly preceding the itinerant left Sod in Explicit, NASA's participating scientist program asked researchers from all over the world to submit changed ideas in behalf of experiments that could be performed with the MSL's already-designed instruments.
Keck Organization Professor of Geochemistry and one of the 29 selected participating scientists, submitted a plan that outlined a defined of techniques similar to those already used throughout dating rocks on Turf, to upon the maturity of rocks on Mars. Findings from the earliest such probe on the Red Planet—published by Farley and coworkers this week in a collection of Curiosity papers in the journal Art Express —provide the maiden age determinations performed on another planet.
The journal is joke of six appearing in the newsletter that reports results from the interpretation of experiments and observations obtained midst Curiosity's examination at Yellowknife Bay—an area of defoliate bedrock in Gale Crater about meters from the rover's deplaning site. The smooth flooring of Yellowknife Bay is made up of a fine-grained sedimentary rock, or mudstone, that researchers conceive was deposited on the bed of an ogygian Martian lake.
In Cortege, Curiosity drilled holes into the mudstone and sedate powdered unnerve samples from two locations about three meters aside. Once the rock samples were drilled, Curiosity's robotic arm delivered the toss powder to the Sampling Analysis on Mars SAM instrument, where it was used fit a selection of chemical analyses, including the geochronology—or rock dating—techniques.
One standard operating procedure, potassium-argon dating, determines the age of a swing sample alongside measuring how much argon gas it contains. Chiefly time, atoms of the radioactive arrangement of potassium—an isotope alarmed potassium—will deterioration within a rock to spontaneously fashion stable atoms of argon
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Here I want to concentrate on another source of error, namely, processes that take place within magma chambers. To me it has been a real eyesight opener to see all the processes that are taking lieu and their potential influence on radiometric dating. Radiometric dating is largely done on rock that has formed from solidified lava. Lava properly called magma ahead of it erupts fills large stealthy chambers called magma chambers.
Uttermost people are not aware of the many processes that filch place in lava before it erupts and as it solidifies, processes that can have a tremendous influence on daughter to parent ratios. Such processes can cause the daughter product to be enriched relative to the parent, which would make the rock look older, or agency the parent to be enriched relative to the daughter, which would make the rock look younger.
This calls the everything radiometric dating scheme into urgent question. Geologists assert that older dates are found deeper poor in the geologic column, which they take as evidence that radiometric dating is giving truly ages, since it is appearing that rocks that are deeper must be older.
But exact if it is true that older radiometric dates are fix lower down in the geologic column, which is open to question, this can potentially be explained by processes occurring in magma chambers which cause the lava erupting earlier to plain older than the lava erupting later. Lava erupting earlier would come from the top of the magma chamber, and lava erupting later would come from lower down. A number of processes could cause the fountain-head substance to be depleted at the top of the magma chamber, or the daughter output to be enriched, both of which would cause the lava erupting earlier to appear darned old according to radiometric dating, and lava erupting later to appear younger.
Mechanisms that can alter daughter-to-parent ratios What happens when magma solidifies and melts and its implications for radiometric dating The following quote from The Earth:
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I found several good sources, but none that seemed both complete enough to stand alone and simple enough for a non-geologist to understand them.
When an atom emits a beta particle, a neutron inside the nucleus is transformed to a proton. These sources are supplemented by references in other books, numerous threads on several CompuServe forums, and other papers and articles downloaded from CompuServe and the World Wide Web. How anyone can keep track of this all is a mystery to me, especially with the difficulties encountered in exploring magma chambers.
When we know how much excess Pb there is, and we know the current quantity of U, we can calculate how long the U in our sample has been decaying, and therefore how long ago the rock formed. Meteoritics and Planetary Science.
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Perfect age dating deals with assigning realized dates in years before the set to geological events. Contrast this with relative age dating, which instead is concerned with determining the orders of events in Earth's past.
Scholars and naturalists, understandably, take long been interested in knowing the absolute age of the Earth, as well as other important geological events. In the 's, practitioners of the young science of geology applied the uniformitarian views of Hutton and Lyell see the introduction to this chapter to try to determine the ripen of the Clay. For example, some geologists observed how long it took for a inured amount of residuum say, a centimeter of sand to accumulate in a modern habitat, thereupon applied this class to the come to known thickness of sedimentary rocks.
When they did that, they estimated that the Earth is many millions of years old. Geologists were beginning to accept the views of Hutton that the Earth is unimaginably ancient. What key discovery, next, allowed geologists to begin assigning total age dates to rocks and at the end of the day discover the seniority of the Earth?
The answer is radioactivity.
An Essay on Radiometric Dating. By Jonathon Woolf http: Radiometric dating methods are the strongest direct signify that geologists have because the age of the Earth. All these channelss point to Earth being very, very old -- several billions of years old.
Young-Earth creationists -- that is, creationists who believe that Earth is no more than 10, years old -- are fond of attacking radiometric dating methods as being full of inaccuracies and riddled with sources of error.
When I ahead became interested in the creation-evolution debate, in belatedly , I looked in the matter of for sources that unquestionably and simply explained what radiometric dating is and why young-Earth creationists are driven to discredit it. I found several passable sources, but none that seemed both complete adequate to stand alone and simple enough for a non-geologist to understand them.
Thus this essay, which is my attempt at producing such a roots.
Am I mad for quitting dentistry for an arts degree???Radiometric Dating: a method of determining the absolute age of an object by comparing Igneous rocks are the best types of rock samples to. Radiometric dating or radioactive dating is a technique used to date materials such as rocks or . Dating can now be performed on samples as small as a nanogram using a mass spectrometer. The mass spectrometer was invented in the..
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- An Essay on Radiometric Dating
Geologist Ralph Harvey and historian Mott Greene explain the principles of radiometric dating and its application in determining the age of Earth. As the uranium in rocks decays, it emits subatomic particles and turns into lead at a constant rate. Measuring the uranium-to-lead ratios in the oldest rocks on Earth gave scientists an estimated age of the planet of 4. Fraction from A Science Odyssey: Geologists have calculated the age of Earth at 4. But for humans whose life span hardly ever reaches more than years, how can we be so sure of that ancient date?