AV-type (volcanic-type) asteroid, orVestoid, is anasteroid whosespectral type is that of4 Vesta. Approximately 6% ofmain-belt asteroids are vestoids,[citation needed] with Vesta being by far the largest of them. They are relatively bright, and rather similar to the more commonS-type asteroid, which are also made up ofstonyirons and ordinarychondrites, with V-types containing morepyroxene than S-types.
A large proportion of vestoids haveorbital elements similar to those of Vesta, either close enough to be part of theVesta family, or having similareccentricities andinclinations but with asemi-major axis lying between about 2.18AU and the 3:1Kirkwood gap at 2.50 AU. This suggests that they originated as fragments of Vesta's crust. There seem to be two populations of Vestoids, one created 2 billion years ago and the other 1 billion years ago, coming respectively from the enormous southern-hemisphere cratersVeneneia andRheasilvia.[1][2] Fragments that ended up in the 3:1 Jupiter resonance were perturbed out of the Kirkwood gap and some fragments eventually hit the earth asHED meteorites.
Theelectromagnetic spectrum has a very strong absorption feature longward of 0.75μm, another feature around 1 μm and is very red shortwards of 0.7 μm. The visible wavelength spectrum of the V-type asteroids (including 4 Vesta itself) is similar to the spectra of basaltic achondriteHED meteorites.
AJ-type has been suggested for asteroids having a particularly strong 1 μm absorption band similar todiogenite meteorites,[3] likely being derived from deeper parts of the crust of 4 Vesta.
The vast majority of V-type asteroids are members of the Vesta family along with Vesta itself. There are someMars-crossers such as9969 Braille, and someNear-Earth objects like3908 Nyx.
There is also a scattered group of objects in the general vicinity of the Vesta family but not part of it. These include:[4]
V-type NEAS (or V-NEAs) arenear-Earth asteroids with aVspectral type. Impacts of V-NEAs on the Earth, according to the known sample (data taken in 2016), occur once in about 12 million years and have the potential to cause disastrous effects on regional to global scale, producing craters as large as 30 km in diameter and releasing kinetic energy of as much as 3Mt. This energy is almost 6 million times greater than the energy released during the Chelyabinsk event in 2013. Venus, Mars and the Moon will experience impacts with V-NEAs every 22 Myr, 125 Myr and 168 Myr, respectively. Two craters with confirmed basaltic impactor which fits with the impact rate found from V-type NEAs are theStrangways crater (24 km diameter) inAustralia, theNicholson crater (12.5 km diameter) inCanada. Some V-NEAs have orbits similar to that of theBunburra Rockhole meteorite.[5]
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