W.M. Keck Laboratory in Astrochemistry

The overall goal of this project is to comprehend the chemical evolution of the Solar System. This will be achieved through an understanding of the formation of carbon-, hydrogen-, oxygen-, and nitrogen-bearing (CHON) molecules in ices of Kuiper Belt Objects (KBOs) by reproducing the space environment in a specially designed experimental setup. KBOs are small planetary bodies orbiting the sun beyond the planet Neptune, which are considered as the most primitive objects in the Solar System. A study of KBOs is important because they resemble natural ‘time capsules’ at a frozen stage before life developed on Earth. Our methodology is based on a comparison of the molecules formed in the experiments with the current composition of KBOs; such approach provides an exceptional potential to reconstruct the composition of icy Solar System bodies at the time of their formation billions of years ago. The significance of this project is that our studies elucidate the origin of biologically relevant molecules and help unravel the chemical evolution of the Solar System. Since KBOs are believed to be the main reservoir of short-period comets, which are considered as ‘delivery systems’ of biologically important molecules to the early Earth, our project also brings us closer to the understanding of how life might have emerged on Earth.

To achieve this goal, we established the interdisciplinary W.M. Keck Laboratory in Astrochemistry comprising researchers from the UH Department of Chemistry (Ralf Kaiser, John Head), UH Department of Physics & Astronomy (Klaus Sattler), the UH Institute for Astronomy (Karen Keech), UH HIGP (Shiv Sharma), UCLA (David Jewitt), and NASA Goddard (John Cooper). The centerpiece of this is a novel ultra high vacuum (UHV) surface scattering machine mimicking the chemical evolution of KBOs. This experimental setup allows a systematic investigation of the formation of new species on the molecular level in low temperature ices by ionizing radiation (solar wind particles and photons, galactic cosmic rays) over a wide range of parameters under ultra clean (10^-12 torr) conditions. By analyzing intermediates and products on line and in situ via infrared, Raman, UV/VIS spectroscopy and time-of-flight/mass spectrometry utilizing soft ionization (low energy electrons, tunable photoionization), the formation routes of newly formed molecules can be extracted quantitatively. Utilizing a scattering chamber, Ralf Kaiser (Chemistry), Klaus Sattler (Physics), and Shiv Sharma (Geochemistry) will investigate experimentally the formation of molecules on KBO surfaces. Theoretical calculations (John Head; Chemistry) are crucial to extend the experiments, which can be carried out only at discrete irradiation wavelengths and kinetic energies of the irradiating particles. These studies are cross linked with observations of KBOs at Keck and Subaru telescopes at Mauna Kea by Karen Meech (IfA) and David Jewitt (UCLA). By comparing model predictions (John Cooper, NASA Goddard) with observations, the models can be refined until an agreement between predicted and observed data is reached and a coherent picture of the chemistry of KBO surfaces emerges.

The four pillars of multidisciplinary collaborations within the interdisciplinary W.M. Keck Laboratory in Astrochemistry

Assembly drawing (left) and front view (right) of the new surface scattering machine (under construction)

Analytical light sources from the infrared (IR) to the vacuum ultraviolet (VUV) in the simulation chamber compared to currently operating space probes (left) and resonant four wave mixing schemes to generate tunable vacuum ultraviolet (VUV) light in the laboratory; mixing schemes involve gas cells and differentially pumped, pulsed jet expansions