Penitentes: where art thou?

 Hidden in amongst the ice penitentes above is PVL PhD student Giang Nguyen! Original image "Penitentes ice formations at the southern end of the Chajnantor plain in Chile in 2005." credit: ESO, https://www.eso.org/public/images/img_1824/

By Tue Giang Nguyen

A great deal of my research recently has been dealing with atmosphere-surface interactions. In conjunction with my survey for dunes on the Martian polar cap, I’ve also been looking for surface features called penitentes. For the uninitiated, penitentes are ice and snow blade structures common in tropical alpine regions such as the Andes and the Himalayas. Although Darwin thought that these ice blades were sculpted by the wind, later glaciological research proved otherwise.

Penitentes are formed by uneven heating and subsequently sublimation of an icy surface. Imagine a pair of mirrors held together forming a v-shape with their reflective surface pointing up. Now from above, if you shine a laser onto the v-shape mirrors, you will probably see that the light will bounce between the walls sending light towards the bottom of the v. This dynamic of light bouncing off the reflective side walls and concentrating towards the depression is how the ridges and troughs of penitentes take their shape. As the trough receives more heat and sublimate more water, it deepens while the side walls receive less heat and sublimate more slowly.

Searching for Liquid Water on Mars at the Canadian Light Source

 

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.