Diamonds, Meteorites, and the Origin of the Solar System.

view Abstract Citations (105) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Diamonds, Meteorites, and the Origin of the Solar System. Urey, Harold C. Abstract In order to explain the chemical composition and physical structures of meteorites, it is proposed that two sets of objects of asteroidal and lunar size were accumulated and destroyed during the history of the solar system. These are referred to as the "primary" and "secondary" objects Since diamonds occur in meteorites, some of the objects must have been of lunar mass or greater; but it is not possible to be certain as to whether this occurred in the primary or secondary objects The ages of the meteorites require that the primary objects accumulated about 4 5 X l0 years ago, were heated by some means to the melting point of silicates and iron, were then cooled to 500 C for l0 -l0 years, and subsequent to this were broken into fragments of less than centimeter and millimeter sizes. The secondary objects accumulated from these about 4.3 10 years ago, and they were at least of asteroidal size. These objects were broken up at some time or times during the last 4.5 X l0 years, and the fragments are the meteorites. These collisional processes occurred during the formation of the solar system. The primary objects must have antedated the time of active formation of the system Solid objects appeared early during the formation of the system and played an important physical role during the formation of the planetary system and possibly in the formation of the sun. It is suggested that the solar nebula consisted of a disk of gas and solid objects and that the dissipation of the gases and some of the solids took place from this disk. Protoplanets in the sense of large masses of gas and dust of solar composition did not occur, at least in the case of the terrestrial planets, and not until much dissipation of the gases and dust had occurred. Publication: The Astrophysical Journal Pub Date: November 1956 DOI: 10.1086/146269 Bibcode: 1956ApJ...124..623U full text sources ADS |