Our universe is filled with high-energy particles and light, which require immense energy from some of the most extreme objects and processes imaginable to create. One of the biggest challenges astronomers face is figuring out how these cosmic rays a
Bring fact-checked results to the top of your browser search. Association of meteorites with asteroids If meteoritic material comes from specific regions of the asteroid belt, then the asteroids in such regions should have the chemical and mineralogical composition observed in the meteorites.
The surface mineralogical composition of asteroids, in principle, can be determined directly by observations from Earth of the fraction of sunlight they reflect albedo and the spectrum of the reflected light reflectance spectrum.
A number of processes conspired, however, to make the association of certain asteroids with the various meteorite groups much more difficult than might be expected.
Opposite hemispheres of the asteroid Eros, shown in a pair of mosaics made from images taken by the U. S class asteroids e. These are the same minerals found in ordinary chondritesbut they also are present in a number of other meteorite types. The C class asteroids e.
It is plausible to consider the C class asteroids as candidate sources for certain groups of carbonaceous chondrite meteorites. Their low albedos and spectral evidence of hydrous silicates, however, make them unlikely sources of ordinary chondrites.
When the S class asteroids were considered in more detail, there were difficulties in identifying them all as sources of ordinary chondrites. Largely because of their apparent range of mineralogies—specifically their ratios of olivine to pyroxene—the S class asteroids have been divided into seven subclasses.
The asteroids in the S IV subclass seemed to have mineralogies that best matched those of the ordinary chondrites. With the notable exception of a low sulfur content, the composition of Eros was found to be consistent with that of an ordinary chondrite.
However, the spectra of the surfaces of S-class asteroids did not match those of ordinary chondrites. The discrepancy was resolved only in when the Japanese spacecraft Hayabusa returned to Earth from the S IV asteroid Itokawa with over 1, particles of dust that had surfaces characteristic of an S-class asteroid but on the inside were identical in composition to ordinary chondrites.
The Hayabusa results showed that the surfaces of asteroids were changed by a set of processes collectively called space weathering that were responsible for both the low sulfur measurement of Eros and the mismatch between the spectra of chondrites and S-class asteroids.
Important component processes of space weathering are the impacts of meteorites and micrometeorites and the impingement of energetic solar wind particles, solar radiationand galactic cosmic rays on surface materials.
Over time these processes act to modify the chemical and physical surface properties of airless bodies such as Mercurythe Moon and some other planetary satellites, and asteroids and comets.
Space weathering must also affect the spectra of the asteroidal sources of the other meteorite groups. Nevertheless, a number of more-or-less-convincing associations between groups of meteorites and types of asteroids have been made.
It has been proposed that the CV and CO groups of carbonaceous chondrites come from the K class asteroids. The most likely source of the iron meteorites is the M class of asteroids, but enstatite chondrites and mesosiderites have also been linked to them.Stellar nucleosynthesis is the collective term for the nuclear reactions taking place in stars to build the nuclei of the heavier elements..
The processes involved were elucidated over a number of years from early in the 20th century, when it was first realised that the energy released from nuclear reactions accounted for the longevity of the Sun as a .
The helium-4 abundance is important because there is far more helium-4 in the universe than can be explained by stellar nucleosynthesis. In addition, it provides an important test for the Big Bang theory.
Meteorite - Association of meteorites with asteroids: If meteoritic material comes from specific regions of the asteroid belt, then the asteroids in such regions should have the chemical and mineralogical composition observed in the meteorites.
The surface mineralogical composition of asteroids, in principle, can be determined directly by observations from Earth of the fraction of sunlight. Index, Illustration, Reference, and Photo Credit. A B C D E F G H I J K L | (go to 2nd index page) M N O P Q R S T U V W X Y Z.
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