Chihuahua Dog Breed. First discovered in Mexico, the Chihuahua is best known for being the smallest dog breed in the world. Extremely loyal to its owner, the breed has recently become a popular culture icon in the United States, most notably Paris Hilton's Chihuahua, Tinkerbell. Physical Characteristics.
Earth formed around 4.54 billion years ago by accretion from the solar nebula. Volcanic outgassing probably created the primordial atmosphere and then the ocean; but the atmosphere contained almost no oxygen and so would have been toxic to most modern life including humans.
While it is very possible Earth and other planets were forming 4.56 billion years ago or earlier, we know planet formation for Earth was finished by at least 4.28 billion years ago. This is only one example; there is no known time frame for planet formation, and each planet may have formed at different times and different rates. Planetesimals The planetesimal theory, put forth by Viktor Safronov in 1941, explains planet formation in the early solar system from accretion of small bodies, growing in size as gravity attracted more and more objects.