Methods of Dating the Age of Meteorites Meteorites are among the oldest objects we know about - formed about 4. But how do scientists know this? This article describes the principles and methods used to make that determination. There are well-known methods of finding the ages of some natural objects. Trees undergo spurts in growth in the radiometrlc and summer months while becoming somewhat dormant in the fall and winter months.
When a tree is cut down, these periods are exhibited in a cross section of the trunk in the form of rings. Simply counting the number of rings will give one a fairly good idea of the age of the tree. Periods of heavy rain and lots of sunshine will make larger gaps of growth in the rings, while periods of drought might make it difficult to count individual rings. When determining the ages of very old objects, the only suitable clocks we have found involve the measurement of decay products of radioactive isotopes.
Isotopes are atoms of the same element with different amounts of neutrons. Some isotopes are stable, whereas others are radioactive and decay into other components called daughter radiomettic. For example, hydrogen has two stable isotopes 1H ordinary hydrogen2H deuteriumand one radioactive isotope 3H tritium.
The meteorits denotes the atomic weight of the isotope the number of protons and neutrons. Radioactive isotopes decay according to a power law, and the typical unit given for this is called the half-life of the isotope. For all practical purposes, the original isotope is considered extinct after 6 half-life intervals. Some of the isotopes and their daughters are shown in the following table from Dodd : The isotopes above the line in that figure are now extinct, since there are no means of replenishing the parent isotope in the Solar System.
Note that there are vast ranges of time exhibited in the decay rates, allowing a suitable measure if one knows or guesses the approximate age.How Radiometric Dating Works: Relative not Absolute Ages
Radiometric dating of the oldest meteorites
- The age of the Earth is estimated to be ± billion years ( × years ± 1%). This age may represent the age of the Earth's accretion, of core formation, or of the material from which the Earth formed. This dating is based on evidence from radiometric age-dating of meteorite The oldest such minerals analyzed to date—small crystals of zircon from the.
- Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to .. Samples of a meteorite called Shallowater are usually included in the . Alexander N. Krot() Dating the Earliest Solids in our Solar System.
- Mar 31, radiometric carbon dating of radioactive dating of the oldest moon rocks; moon rocks, they have ages of meteorites need updating. The rocks.
- Zircon Chronology: Dating the Oldest Material on Earth from western Australia dates back – billion years, and we know from meteorites that the Earth is.
- This age has been determined with the radioactive dating technique. The oldest meteorites ever dated in the Solar System are 4,56 billion years old, the oldest.
- The oldest rocks on Earth found to date are the Acasta Gneiss in that have fallen to Earth have had their ages calculated by radiometric dating. The Canyon Diablo meteorite is important because it represents a class of.
Therefore the age of the Sun should be close to the age of the meteorites, which can be found using the method of radioactive dating. The oldest fossils, found in Australia, are about 3. In one note, from Dr. Some isotopes are stable, whereas others are radioactive and decay into other components called daughter isotopes. When determining the ages of very old objects, the only suitable clocks we have found involve the measurement of decay products of radioactive isotopes. Since it was pretty well acknowledged that the oldest rocks on Earth were younger than the Earth itself the Earth having been molten in its early days , Patterson turned to meteorites, judging that the oldest meteorites and the Earth formed at about the same time. A small portion of a meteorite is vaporized in the device forming ions.However, there will also be some unknown amount of 87Sr that was in the meteorite when it formed. Thus, although "extinct", these nuclides are present in meteorites, but produced by a more recent process. Isotopes are atoms of the same element with different amounts of neutrons. He worked with a number of meteorites, and especially with fragments of the Canyon Diablo meteorite first imagewhich formed Meteor Crater in Arizona second image. This may seem odd at first, but in fact it is extremely likely that the solar system i. Amazingly, 60 years later, this is still the textbook age of the Earth. Only the latter two "extinct" nuclides are used in dating. The ions are deflected according to their mass. Note that there are vast ranges of time exhibited in the decay rates, allowing a suitable measure if one knows or guesses the approximate age. Christensen-Dalsgaard et al. For all practical purposes, the original isotope is considered extinct after 6 half-life intervals. Increasingly, the radiometric dating of the oldest meteorites techniques are used, such that probably no one technique dominates for meteorite dating. By taking samples from various parts of a meteorite and plotting these results, the data will fall on a straight line whose slope characterizes the age of the meteorite.
Radiometric datingPatterson is one of the most unsung of the great 20th-century geologists. His specialty was geochronology—the dating of the Earth. Ever sincewhen radiometric dating was first proposed, the datung technique for dating the Earth had been the same: compare the amount of uranium in a rock with the amount of its radioactive decay byproduct, a specific isotope of lead. The more lead and the less uraniumthe older the rock.
Zircon Chronology: Dating the Oldest Material on Earth
Scientist of the Day - Clair Patterson
Age of the Earth
By adjustment of the strength of the magnetic field and suitable placement of an ion collector, the different isotopes can be measured with precision. Scientists use a mass spectrometer to obtain these ratios. One complication of checking the Solar Model with our real Sun is the quantity of helium: the "helium abundance. These ions are accelerated in an electric field through collimating slits and subject to a magnetic field which causes the ions to follow a curved path. Actually, meteorites that formed by melting, e.
The oldest fossils, found in Australia, are about 3.How old is the Sun? There are several independent ways of estimating the age and they all give nearly the same answer: about 5 billion years. The age of the Sun can be estimated from the ages obtained from radioactive dating of the oldest meteorites. This may seem odd at first, but radiojetric fact it is extremely likely that the solar system i. Therefore the age of the Sun should be close hhe the age of the meteorites, which can be found using the method of radioactive dating. Wasserburg obtained a meteoritic age of 4. GuentherAstrophysical Journalestimated that hydrogen burning started shortly thereafer 40 million 0. Additional evidence comes from the Earth. The oldest Earth rocks are also about 4. The oldest fossils, found in Australia, are about 3. The presence of fossils in rocks indicates that the Earth was a suitable place for life when the fossils formed. This implies that the Sun was luminous at that time. Viewing the Sun as a star on the main sequence, is very useful and important for astronomers because they have a model called "The Standard Solar Model" that views the Sun at stages in its life while it is burning hydrogen and converting that to helium. The model can be run forward and backward in time, and the astronomers can check the observable quantities in the model like luminosity, solar radius, metworites, solar p-mode frequencies, and so on with our real Sun. They can stop the model at any time during its main sequence. If what we see from our Sun matches the quantities in the model for a specific age, then we have one more piece of information of what we think that the age of the Sun is. One complication of checking the Solar Model with our real Sun is the quantity of helium: the "helium abundance. Oldesg to the Dalsgaard article see belowthe solar spectrum is too complicated to accurately measure the helium abundance, so that one parameter has to be estimated one infers the helium abundance by matching the observed solar radius and luminosity in the solar models.