The Continuing Adventures at the Canadian Light Source

This past February, a team from PVL once again descended on the Canadian Light Source (CLS), pictured above, to learn more about the conditions that prevailed in the atmosphere of early Mars and maybe even to learn something that could help current-day orbiters understand their results.

By Charissa Campbell

Recently, some of the PVL team traveled back to the University of Saskatchewan in Saskatoon to perform more experiments at the Canadian Light Source (CLS). Our first trip was discussed by project lead, Dr. Paul Godin in a previous PVL blog post (http://york-pvl.blogspot.com/2018/11/searching-for-liquid-water-on-mars-at.html). Unfortunately our U of T member (Tyler Wizenberg) could not attend this trip because he was traveling to the arctic for experiments at the same time. To fill his shoes, PVL PhD candidate Giang Nguyen tagged along.

For some background information, the purpose of these experiments is to better understand how liquid water could have existed on the surface of early Mars. Currently, Mars atmospheric models have not been able to show the surface temperature rising above 0°C. However, abundant evidence of erosion by water has been seen from orbit and there are surface geological experiments pointing towards liquid water having been present on the surface (https://www.jpl.nasa.gov/news/news.php?feature=4398). 

If water erosion is evident then there must be another explanation for warming in the ancient Martian atmosphere that current atmospheric models cannot explain. This is where our experiment comes in: looking at the collision-induced absorption (CIA) of greenhouse gases to test a theory from Wordsworth et al. (https://doi.org/10.1002/2016GL071766) that these gases might provide additional atmospheric absorption not currently included in models that would allow surface temperatures to rise. If our experiments agree with Wordsworth's models, it may be another piece to the puzzle towards understanding water and early Mars.

So why do we need to go all the way at the CLS for these experiments? They have the perfect set-up for us to measure the CIA which we cannot find at home. Plus, a little trip outside of Ontario is always nice, especially for scientific research. However, we had several days of -30ºC to -40ºC weather which was a “fun” end to winter as Toronto felt warm and balmy when we got back! One change between our last trip and this one was that the CLS fixed their electron gun that had put operations down for over 6 months (https://www.lightsource.ca/news/details/cls_extends_shutdown_to_repair_electron_gun.html). The consequence of the beamline not being operational was that the facility was fairly quiet. Fortunately, the CLS was a lot busier this round which was a nice change. It's always great to see a scientific facility busy.

In the last round we ran out of time to complete our experiments, so these were at the top of our list for this round. We also repeated some of the methane measurements from the last visit because our results were saturated by the amount of methane we put into the cell. This can be corrected by lowering the quantity of methane for our experiments. The small methane tank we used was more than enough for all the measurements, so we didn’t have to do a lot of walking, as we did the last time. Since methane is considered a flammable gas, we had to use a special filling station to ensure it had proper airflow in case of leakage. This filling station is on the opposite side of the CLS from where our lab was, so we had to do several trips last round just to fill the cell with the amount of methane we needed. Unfortunately, that means I got significantly less steps on my Fitbit because we didn’t have to do those long trips for methane. Between that and the duration of the experiments (1-2 hours) there was a lot of downtime. Since I had just submitted a journal paper based on my MSc thesis, I took the opportunity to catch up on some research.

For our hydrogen measurements, we got to use a new machine that used electrolysis to put hydrogen into the cell. This method (see the corresponding figure below) uses electricity to separate water into its constituents: hydrogen and oxygen. To use hydrogen during the last round, we used a mixture gas that contained carbon dioxide and a percentage of hydrogen. Since hydrogen is also considered a dangerous gas, it cannot be used directly. Having this machine was useful because we could control the hydrogen percentage instead of being confined to either 4% or 8% that our tanks had last time. However, we discovered a decent amount of water spectral lines within our data when we processed an experiment after using it. This indicates that water had gotten into the cell which makes our data less accurate. Since the electrolysis machine took water to get hydrogen, we assumed that the water must have been going into the cell somehow. We decided to go back to our mixture gases to ensure we didn’t have any water in our experiments. Even though we didn’t use the electrolysis machine extensively, it was still interesting to see this innovation in the lab to aid in using pure hydrogen from a simple and easy method. 

We also added on new experiments using Carbon Monoxide (CO). The purpose of this was to compliment measurements taken by the Trace Gas Orbiter (TGO). TGO is a satellite currently orbiting Mars that is attempting to understand methane and other small concentrated atmospheric gas, such as CO. Comparing our results to the TGO results could help confirm our method for understanding greenhouse gases for early Mars and would also help the TGO team to interpret their own results.

Overall, things went smoothly during this run and we didn’t have many hiccups. There may be a third trip to the CLS in the future, but that will depend on how our data looks from this trip. If we do end up going back for a third round, hopefully we can schedule it during the summer to take advantage of the nice prairie summers and severe thunderstorms rather than the frigid cold!