The Early Evolution of the Inner Solar System: A Meteoritic Perspective
C. M. O'D. Alexander,
A. P. Boss,
R. W. Carlson
Formation of the solar system may have been triggered by a
stellar wind. From then on, the solar system would have followed a
conventional evolutionary path, including the formation of a disk and
bipolar jets. The now extinct short-lived radionuclides beryllium-10
and, possibly, manganese-53 that were present in meteorites probably
resulted from energetic particle irradiation within the solar system.
Calcium-aluminum-rich inclusions (the oldest known solar system
solids) and chondrules could have been produced by the bipolar jets,
but it is more likely that they formed during localized events in the
asteroid belt. The chondritic meteorites formed within the temperature
range (100 to 400 kelvin) inferred for the midplane of classical T
Tauri disks at 2 to 3 astronomical units from their central stars.
However, these meteorites may retain a chemical memory of earlier times
when midplane temperatures were much higher. Dissipation of the solar
nebula occurred within a few million years of solar system formation,
whereas differentiation of asteroidal-sized bodies occurred within 5 to
15 million years. The terrestrial planets took ~100 million years to
form. Consequently, they would have accreted already differentiated
bodies, and their final assembly was not completed until after the
solar nebula had dispersed. This implies that water-bearing asteroids
and/or icy planetesimals that formed near Jupiter are the likely
sources of Earth's water.
Department of Terrestrial Magnetism, Carnegie Institution of
Washington, 5241 Broad Branch Road, N.W., Washington, DC 20015, USA.
