Contrary to the planetesimal
theory, the article asserts, Earth's complete, protoplanetary condensation initially formed a gas-giant planet virtually identical in mass to Jupiter.
See was critical of the planetesimal
hypothesis, as it was known, and in 1909 attacked it in terms that drew a sharp response from Moulton, implying amongst other things that See, one of his former teachers at Chicago, had plagiarised his work; a charge he reiterated with biting sarcasm in a 1912 February critique 'Capture theory and capture practice', published in Popular Astronomy.
Nevertheless, we have come to realize that these impacts not only contributed to forming our planet (through planetesimal
collision and accretion), but also by modifying it through time, and even punctuating the path of life's evolution.
Ward has also contributed fundamental insights to humankind's understanding of planetesimal
formation, the dynamical evolution of the moon, planet migration, planetary spin axis orientations, and the formation of planetary and satellite systems.
The present consensus is that the Moon formed as the result of a giant impact of an approximately Mars-sized planetesimal
with the proto-Earth.
Heating caused by the decay of radioactive elements causes a melting process that results in iron metal segregating to the centre of the forming planetesimal
, while the most volatile elements move into the atmosphere.
Whether the four inner planets or a migrating Jupiter nudged the planetesimal
toward the asteroid belt is unclear, the team reports.
As a theoretician, Ward has contributed fundamental insights to humankind's understanding of planetesimal
formation, the origin and dynamical evolution of the moon, planet migration, planetary obliquity mechanics, and the formation of planetary and satellite systems.
The presence of aluminum-26 in a meteorite whose parent asteroid is known to have undergone early melting "helps buttress the case for aluminum-26 having been a major source of energy for planetesimal
heating," he adds.
Their gravity then flung Uranus and Neptune out into the planetesimal
disc like bowling balls, causing the objects there to scatter like pins.
Their dynamical, radiative and thermodynamic properties critically define the environment for embedded solids: dust grains, pebbles and planetesimals
As Jupiter moved inward, however, gravitational perturbations from the giant planet would have swept the inner planets (and smaller planetesimals
and asteroids) into close-knit, overlapping orbits, setting off a series of collisions that smashed all the nascent planets into pieces.