This Wednesday will be the midpoint of the weeklong MetSoc meeting, going on right now (see Day 1, Day 2). Today is quite light, ergonomically, but heavy pedagogically. Conel Alexander has spent his career in cosmochemistry, and not just “in the trenches”; his work includes the serious questions of the formation of the Earth and Solar System.
https://www.hou.usra.edu/meetings/metsoc2025/technical_program/
Wednesday, July 16, 2025
Leonard Medal
THE METEORITICAL SOCIETY presents THE 2025 LEONARD MEDAL to Conel Alexander for his major contributions to understanding thesources and behavior of organic material and water in the solar system, the nature and origin of chondrules, and presolar grains.
Leonard Medal Lecture: The Carbonaceous Chondrite Formation Locations and Other Problems [#5109]
It’s been decades now: we’re pretty sure the ordinary chondrite meteorites formed in the inner Solar System (as fragments of S-type or S-complex asteroids), while the carbonaceous chondrite meteorites (and their C- or C-complex asteroidal parents) represent the outer Solar System. The ordinary chondrites are quite poor in water and organics, while the carbonaceous chondrites are water-rich and riven with organics. This makes perfect sense if the C-bodies formed beyond the “snow line”, the radius in the Solar System where it’s cold enough for water to condense. But, other than that, what were the details of that early Solar System? Alexander reviews the evidence and train of logic. “Carbonaceous chondrite” is a category, not a club membership, and there are subtypes within it. What is the relationship between subtypes, and between C-asteroids and comets? That line gets blurrier and blurrier as we discover more types. For that matter, some of the old evidence is now in question, in light of some space missions of the modern era. Are we getting closer to pinning down the arrangement of Jupiter, Saturn, the small bodies around them, and the balance of the Solar System?