On Wednesday, December 6, 2023 I attended a Mike A’Hearn lecture with Karen Meech in the second lecture of a series titled “Small Bodies”. This lecture focused on comets or as the series titled the “Primitive Witnesses to the Birth of a Habitable Solar System”.
Meech began her lecture by reviewing the definition of Astrobiology and how it seeks to understand how habitable worlds are made. She noted the importance of new technologies in these discoveries and that even though our solar system is the only one currently to have livable conditions, it is possible that our solar system may be extremely unusual when it comes to others in the galaxy. Meech then continued to discuss the importance of water in the process of life on a planet. After this she broke down the timeline of water on earth and explained how, due to earth's proximity to the sun, it was able to sustain life. She then began to present the possible methods of how Earth's water came to be.
The methods included explaining how H2O could have stuck to dust and other particles at the formation of earth, how through complex chemical reactions earth could have manufactured its own water, or, how objects formed in the ice region (outside of what we now call the asteroid belt) and were water rich may have collided with earth and water became trapped in the atmosphere.
This was one of the more fascinating lectures that I have ever attended because I knew next to nothing about the topics discussed. One of Meech’s main points focused on the importance of interdisciplinary sciences. She noted the important role comets play a large role in bringing water to the earth similarly noting how meteorites also play a similar role as well.
She noted that at very low temps in cold dark clouds the deuterium is enriched and help sustain the D/H of the disk. Because of this comets are elevated and have extremely far and long orbits. The long period comets would not have been able to provide enough data and some of the short period comets provided even less. However, this is an easier process for meteorites and we were able to see that they brought a lot of water, however the chemical properties were not matching up.
Meech went on to mention that along with ocean/atmospheric water there is water located inside the earth and this primordial water measured from helium isotopes. This D/H inside the earth is way lower than the oceans. She then supported this with the fact that in order to publish and continue her research she needed help from chemists and geologists, fields that she knew little about.
She then highlighted another possibility of water on earth mentioning how Jupiter formed early adding another disk preventing dust and particles moving inward towards the sun and inner/terrestrial planets. However, things may have slipped through the gap and this happens when they are big enough gravity throws them inward this would be a “perfect” way to track the water sources but she would need record history of where the icy bodies were formed as well as a source to get close enough to observe in detail.
At the end of the lecture I was absolutely blown away by this topic and how there is still so much that even some of the brightest minds do not yet know. Meech noted the importance of asking questions, because the more you ask the more you learn and the more possibilities become available to you. While at times throughout the lecture I was slightly confused it was very reassuring to see the many different supported hypotheses that are currently unfolding about this topic.