PVL is branching out in time! Not content to limit ourselves to today's Volatile Reserves on Mars, two members of the group, PDF Paul Godin and PhD Candidate Charissa Campbell headed out to Saskatchewan to examine the ancient atmosphere. In the image above, Paul Godin (York), Tyler Wizenberg (U of T), and Charissa Campbell (York) are pictured in front of the Canadian Light Source.
by Dr. Paul Godin
A recent paper by Wordsworth et al. (https://doi.org/10.1002/2016GL071766) suggested that the greenhouse effect on ancient Mars could be stronger than previously thought due to a phenomenon called collision induced absorption (CIA). CIA is when molecules in a gas collide with each other and for a brief moment form a two-molecule complex that has its own absorption features.
Wordsworth’s paper made a computation prediction of what the CIA for the Martian atmosphere would look like, but experimental verification of their prediction is still required. CIA is a weak absorption feature and requires spectroscopy set-ups that have long path-lengths or can handle high pressures to detect it. One method to achieve a long path length is known as a multi-pass White cell; in this set-up mirrors are placed at both ends of the cell and a beam of light is bounced back and forth between them (as shown in Figure 1), allowing for more time for the light to interact with the gas.
Figure 1: White cell configuration. Three mirrors are used to reflect a beam of light multiple times inside the cell.
Unfortunately, the PVL doesn’t have a White cell, but the Canadian Light Source (CLS) synchrotron research facility in Saskatoon does have one. And so, a collaboration between York and U of T was formed that sent three researchers to Saskatoon for two weeks.
The CLS houses the only synchrotron in all of Canada. A synchrotron accelerates electrons in a circle to produce a bright coherent light source. While we were in Saskatoon, the synchrotron was under repair, which was fine for us, since we only needed to use the White cell and not synchrotron radiation.
Figure 2: Inside the CLS. The acceleration ring for the electrons can be seen. This circular acceleration produces extremely bright radiation, allowing the CLS to call themselves “The Brightest Light in Canada”.
The White cell is part of the FAR-IR beamline of the CLS. It connects to a Fourier transform spectrometer that can use a variety of different light sources. Time at the CLS is limited, so in order for researchers to get the most out of their visits the facility runs 24/7. We worked in shifts and often stayed in the lab till 3AM.
Figure 3: FAR-IR beamline of the CLS. The metal cylinder in the centre of the image is the White cell and the “L” shaped box around it is the Fourier transform spectrometer.
Most of our time was spent in the FAR-IR lab, but due to safety concerns surrounding the flammable gases we were using, we weren’t allowed to store the gases in the lab. So, to get our gas samples into the lab we had to transport a small amount of flammable gas to the lab using a small gas tank, which we had to cart back and forth from the far side of the CLS each time we needed to fill the White cell.
Figure 4: Charissa filling our small methane tank from a larger methane tank that is kept safely inside a fume hood.
The CLS has accommodations a short walk away from CLS. The accommodation is a former seminary that was purchased by the CLS several years ago known as Ogle Hall. Normally Ogle Hall is full of CLS users, but since the electron gun was under repairs there were only a few other people staying at the Hall along with us.
Figure 5: The accommodations for the CLS. Ogle Hall used to be a seminary before it was sold to the CLS.
Most of our time in Saskatoon was spent at the CLS, without much time for exploring the city. Luckily for us there was one point of interest right beside Ogle Hall: a field of sculptures. In an adjacent field there was a collection of various sculptures and art pieces scattered throughout the field. We never were able to find out the where these pieces came from, but they certainly were one of the more memorable aspects of our visit to Saskatoon.
Figure 6: Field of statues near Ogle Hall. This image only captures about half of the art pieces.
Ultimately, the trip was a success with lots of measurements taken. However, due to a few minor set-backs, we couldn’t get all the data we wanted so we’ll likely be back again in 2019. Now begins the task of analysing the results to determine how they compare to Wordsworth’s original prediction.
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