NASA Researchers Find Evidence of Planet-Building Clumps
Aug. 21, 2018
NASA scientists have found the first evidence supporting a theory that golf ball-size clumps of space dust formed the building blocks of our terrestrial planets.
A new paper from planetary scientists at the Astromaterials Research and Exploration Science Division (ARES) at NASA’s Johnson Space Center in Houston, Texas, and NASA’s Ames Research Center in Silicon Valley, California, provides evidence for an astrophysical theory called “pebble accretion” where golf ball-sized clumps of space dust came together to form tiny planets, called planetesimals, during the early stages of planetary formation.
“This is very exciting because our research provides the first direct evidence supporting this theory,” said Justin Simon, a planetary researcher in ARES. “There have been a lot of theories about planetesimal formation, but many have been stymied by a factor called the ‘bouncing barrier.’”
"The bouncing barrier principle stipulates that planets cannot form directly through the accumulation of small dust particles colliding in space because the impact would knock off previously attached aggregates, stalling growth. Astrophysicists had hypothesized that once the clumps grew to the size of a golf ball, any small particle colliding with the clump would knock other material off. Yet, if the colliding objects were not the size of a particle, but much larger – for example, clumps of dust the size of a golf ball – that they could exhibit enough gravity to hold themselves together in clusters to form larger bodies."
More:
https://www.nasa.gov/feature/nasa-researchers-find-evidence-of-planet-building-clumps