Oscillating chemistry in zero gravity
How did life originate?
A simple and short question, but one that has driven humankind for millennia. Still, nobody knows the answer. The beginning exploration of space and the rise of exoplanet science with its discovery of temperate worlds open up a new avenue in the search for the origin of life. Multidisciplinary research and pioneering laboratory studies have shown potential pathways for abiogenesis, forming precursors for RNA (e.g. Powner et al., 2009; Patel et al., 2015; Xu et al, 2018; Rimmer et al., 2018). But do the mechanisms working in a laboratory, and proposed to work on a young Earth, also work in more extreme environments?
What if life has not actually formed on Earth? Some theories postulate that life might have formed on asteroids, and was then distributed onto Earth (e.g. Ciesla & Sanford, 2012). Moreover, in our search for habitable exoplanets, one can wonder if and how life might have originated on very extreme planets - ones ranging from the size and low-gravity of the Moon to so called Super-Earths, that can have up to 8 times the surface gravity of our Earth.
Our goal is to study if this Earth-bound prebiotic chemistry could also work in extreme environments ranging from zero G to multiple G, by investigating how altered gravity affects the mixing and reaction rates, accelerating or decelerating the chemistry. To answer this, we are designing a set of experiments to be conducted over the next 10 years which will help us to answer this question. In our first proposal in this series, we want to make use of the unique opportunity provided by a hyperbolic zero gravity flight, which will let us experience a fluent variation of gravity environments. In doing so, we will build up on and expand the scope of previous experiments (e.g. Fujieda et al., 1996, 1999).
In this study, we develop a robust, compact, and simplified version of the Briggs-Rauscher experiment, an oscillating chemistry event often called the Iodine clock. The hypothesis to be tested is that different gravity environments do not change the reaction rates of this oscillating chemistry experiment. Based on the three main components Potassium Iodate, Hydrogen Peroxide and Starch, the reaction changes color from blue to amber in a cyclic way. See the below schematic for a full overview of the reactions. Each color cycle takes about 20 seconds, and a total of circa 10 cycles are completed. The full experiment will run for about 3 minutes. See Video 1 for one cycle of the reaction, hosted in our flight setup. The final assembly and detailed design drawings can be seen in Figs. 1-3. A full overview of the reactions is given by Schematic 1.
In the parabolic flight, we will be able to experimentally measure the reaction rates by monitoring the color change over all 10 cycles, which will let us iterate through 2-3 flight parabolas. We will record the color change using optical video cameras, mounted onto the experimental setup (Fig. 3). In the post-processing and video analysis, we will extract the color information from each video pixel, and record a time series of the color expression. We will mount two TERMITES sensors on the setup, which will record the 3D acceleration, temperature, pressure, and more during flight (Fig. 4). We will then cross-correlate these color time series with the TERMITES’ accelerometer time series (Fig. 5).
Our experimental setup allows for 2 x 4 experiments, whereby 4 experiments will be conducted at the same time, allowing us to assess the standard deviation intrinsic to the experiment. Finally, we will compare the outcome of the 2 x 4 flight experiments with our ground-based laboratory studies, to see whether any significant changes have occurred. Our laboratory studies will be conducted at 1 G (Earth gravity), as well as in centrifuges to assess the dependency of 1-2 G environments.
Video 1: One full cycle of the Briggs-Rauscher reaction, changing color from blue to amber and back to blue within 20 seconds; hosted in our final setup. Credit: Maximilian N. Günther
Figure 1: The full design, with the acrylic block at its center, the mounting stage and camera above, and everything eluminated by an LED strip. Credit: Maximilian N. Günther
Schematic 1: the steps taking part during the Briggs-Rauscher reaction.
Figure 2: The CAD modeling and resulting design drawing for the clear acrylic block. Hosting the Petri dishes and syringes, this is the heart of the setup. Credit: Maximilian N. Günther, Joel Villaseñor, Richard Hall
Figure 3: The CAD modeling and resulting design drawing for the camera mounting stage. Credit: Maximilian N. Günther
Figure 4: A TERMITES sensor, which we will use to monitor the 3D acceleration, temperature, pressure, and more during flight. Credit: Carson Smuts
Figure 5: Example of TERMITES data taken with termites on a Zero G flight in 2018. The orange curve shows the acceleration in z-direction, reflecting the gravity experienced during the parabolas. Credit: Carson Smuts
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