Showing that chondrules
are as old as CAIs addresses a long-standing question of why chondrule
formation should be delayed by up to 2 million years after CAIs.
Most stony meteorites contain chondrules
. Using a jeweler's loupe that magnifies at least 10 x , one can usually spot these tiny spherical inclusions on a chondrite's surface.
Benton reveals a sequence of events that reflect a complex history: (1) chondrule
formation and initial assembly; (2) brecciation; (3) thermal metamorphism and (4) shock veining.
They derive their name from their main component -- chondrules
, which formed as molten droplets floating in space.
This technique enabled the researchers to study the orientation and position of individual micrometre-sized grain particles that had coalesced around the chondrule
themselves formed through quick melting events in the dusty gas cloud -- the solar nebula -- that surrounded the young sun.
"With their high precision measurements, they are able to date formation times for chondrules
very precisely," he said.
Achondrites (which lack chondrules
) are prized by scientists and collectors alike because they come from the Moon, Mars, the asteroid Vesta, and other geologically differentiated bodies.
These findings suggest that chondrules
formed from 2 million to 5 million years after inclusions appeared.
The early family tree of our solar system's rocky planets features tiny glassy spheres called chondrules
, found today inside ancient meteorites.
In the equivalent of nine pages, you get a fast-forward account of how the solar system came to be, and in the process you are introduced to such terms as refractory inclusions, chondrules
, and devolatilized.