There are two major considerations for understanding the presence of water in asteroids. Was water present at formation? And how is water concentration affected by thermal alteration from its environment?

In general, the carbonaceous chondrite meteorites are primitive, having undergone the least amount of alteration and closely matching the chemical makeup of the solar nebula from which the Solar System formed. The CM and CI meteorites are sub-types of carbonaceous chondrites that are known to contain the highest concentration of water. There are still many discrepancies between the taxonomies of meteorites and asteroids. Spacecraft missions can look at asteroids up close and return samples to Earth for study, but meteorites are nature's cheapest version of "sample return".

The core aspect of the study focused on thermal alteration by measuring the release of certain trace elements as the meteorite was heated. Thermal alteration helps tell the story of a rock's journey through various processes in the evolution of the Solar System. Did this rock always reside in a small, primitive asteroid relatively unchanged for billions of years? Did it accrete into a larger planetessimal that partially melted or differentiated? Did it spend some time orbiting really close to the sun or did it migrate from further out? Each of these scenarios involves a distinct thermal environment, so understanding that history helps to piece together what happened to a meteorite in space before it impacted Earth.

There are notable similarities between the asteroid Bennu and carbonaceous chondrites meteorites. In fact, a co-author of this study is planetary scientist Dante Lauretta, the Principle Investigator of NASA’s OSIRIS-REx mission, which will return samples from the asteroid Bennu in 2023.