What have we learned about the distribution of water and organic molecules in the solar system from studies of fluid inclusions in meteorites and mission return samples?

For millennia humans have pondered the question "Are we alone in the universe?" In recent decades the search for evidence of life beyond earth has focused on the search for habits in which liquid water is now or has in the past been present, as well as the search for organic molecules in extraterrestrial (ET) samples. These efforts have, in turn, spurred significant technological advances to develop methods to analyze fluid inclusions (FI) in ET materials, including meteorites and more recently ET samples collected and returned to earth by various missions that have visited a variety of planetary bodies.

 

Some early reports of fluid inclusions in meteorites in the 1970s were later found to be artifacts introduced during sample preparation. As a result, the study of FI in extraterrestrial samples entered a dark period in which any reports of FI in meteorites were dismissed as likely representing fluids introduced after the samples reached earth. The study of FI in ET samples gained renewed interest following the discovery and documentation of aqueous FI in halite in the Monahans (1998) H5 chondrite. The halite and its contained FI were clearly present before the meteorite reached earth, and subsequent studies confirmed that the age of the halite and its contained FI was 4.7 ±0.2 Ga. This discovery spurred new interest to search for FI in meteorites, now using sample preparation methods that avoid introducing water or other fluids into the sample. 

 

In the last two decades much progress has been made in identifying FI in meteorites and mission returned samples, and there are now dozens of well documented reports of FI in these samples.  The rarity of FI in ET samples, combined with the generally small size of the FI (less than approximately 1-2 microns in many cases), has led to efforts to develop and improve analytical techniques to characterize the FI. To this end, our group has determined the bulk chemical and H & O stable isotopic composition of individual FI in Zag and Monahans (1998) halite and asteroid Ryugu pyrrhotites using cryo-Time of Flight Secondary Ion Mass Spectrometry (cryo-TOF-SIMS). In this presentation we will summarize some of these recent efforts involving careful and sophisticated sample preparation and analysis methods.