Dr. Joseph Razzell Hollis
Postdoctoral Fellow At NASA’s JPL

After completing his PhD Dr. Razzell Hollis, who was still interested in space and the possibility of life elsewhere, contacted Dr. Luther Beegle at NASA’s JPL, the principal investigator of SHERLOC. He wanted to see if he could apply his knowledge of quantitative Raman spectroscopy of organic solar cells to the interpretation of deep UV Raman spectra obtained from Mars. He submitted a proposal and received funding for a NASA postdoctoral fellowship, a significant achievement in its own right.

Dr. Razzell Hollis is responsible for streamlining the data analysis process. When data is acquired and returned to Earth, he must determine how to extract information from the spectra and images as efficiently as possible. Due to a custom instrument that generates custom data formatting, Dr. Razzell Hollis had to learn Python. Although he does not think it to be a critical skill, he highly recommends that any aspiring spectroscopist learn to code. “You can incorporate your own functions that are not available elsewhere.” He performs a lot of custom coding to minimize human intervention from baselining spectra to extracting peak positions from fittings. Concurrently, him and his team collect a library of UV Raman spectra of different organic compounds and minerals relevant to the Mars environment, so that when the spectra from the unknown samples return, they immediately have something for comparison.

An integral part of the Perseverance’s goal is to collect samples that will be picked up by a future Mars mission. If a sample of interest is found, the arm of the rover must extract some of that material, put it in a tube and seal it before it drives off to another location. He explains, “We’re looking at raw data and making interpretations because it informs the decisions being made for what the rover’s going to do next.” As practice, a bunch of his colleagues went out in the field with cameras and portable Raman instruments so Dr. Razzell Hollis and his team could compile a list of commands for the rover. By the next day the data would return and they would have to analyze the spectra and images under restricted circumstances and strict time constraints. “Going through this process is very exciting, which is not like any spectroscopy I have ever done before,” he says with a smile.

Dr. Razzell Hollis conducts his research by doing what any productive scientist does: ask questions. He asks himself how light is introduced to a sample by the instrument, how it interacts with the molecules in the sample and how the scattered light returns to the spectrometer to produce the observed spectrum. In one study, he came up with an optical model to describe how light from the laser interacted with the sample. He used an unconventional laser beam, not a cylindrical one but an annular one, in which the majority of light intensity was quite far from the centre, resulting in a very different volume to analyze.1 “I was able to determine exactly how that light interacted with that volume and how that image projected through the instrument onto the detector influenced the signal and the width of the peaks,” he says. “It was an attempt to learn how far into the sample the laser penetrates.” By the time he completed his final equation to describe the propagation of the laser intensity through the sample volume, it spanned two to three lines of text.

In his role at NASA’s JPL, Dr. Razzell Hollis is an astrobiologist, but interestingly enough, he never formally studied astronomy or biology. This shows that passion and strong work ethic can take you a long way. In his next career move, he plans on pursuing a Marie Curie postdoctoral fellowship at the National Museum in London where he will be investigating the impact of microplastic pollution on seabirds. He believes science is not a fixed path and changing disciplines has given him a unique perspective that makes him a better scientist. With his diligence, intelligence and dedication to the field of science and applied spectroscopy, it will be exciting to see all that he accomplishes.

 Reference:

1) An Optical Model for Quantitative Raman Microspectroscopy; J. Razzell Hollis, D. Rheingold, R. Bhartia, L.W. Beegle, Appl. Spectrosc. 2020, 74, 684-700.