I am a Planetary Science Graduate Student at the University of Arizona working for Dr. Shane Byrne. My broad area of research involves observations and modeling of geologic processes on terrestrial bodies in the solar system, with a particular focus on Mars. I study processes that occur due to changes in the distribution of volatile elements on the surfaces of solid planets, such as water on Earth, carbon dioxide on Mars, and nitrogen on Neptune's satellite Triton. Currently, I am studying the geologic and climatic history of Mars, through the detailed analysis of the stratigraphy preserved in the polar deposits of the planet.
My main interests are concerned with geomorphic processes related to volatile elements on solid bodies. My goal in most of my projects is to characterize geomorphic features, processes, and/or patterns through the interpretation of spacecraft observations, and attempt to explain their origin or significance by means of mathematical models and tools that simulate the physics that govern the environment around them, or that aid in the interpratation of particular patterns in the geomorphology, as is the case with stratigraphic analysis.
During my first years in graduate school I studied a series of bright "halos" that appeared around pits and depressions on the south polar resiudal cap (SPRC) of Mars. These halos have only recently been discovered by the High Resolution Imaging Science Experiment (HiRISE) aboard the Mars Recconnaissance Orbiter (MRO). The most interesting fact about them is that they were only prominent during a short period of a particular Mars year, around martian southern summer of "earth year" 2007. I used HiRISE and Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) observations to investigate the optical characteristics of the halos, and the conditions of the cap when the halos appeared. The SPRC is composed entirely of solid carbon dioxide, and it represents the portion of condensed carbon dioxide that persists through the summer on Mars' surface. During the year the halos appeared, there was a large global dust storm on Mars, around mid-southern summer. We therefore believe that these bright halos are the result of a difference in sublimation rates between the sloped walls of depressions, and the flat plains nearby, which would have generated a sublimation driven-wind that caused less dust from the air to be deposited near the walls of the pits. The implications of this are more profound than they might seem at first. Since we didn't observe similar halos in subsequent years, we can conclude that the layer of ice which contained them is not being exhumed, which implies that the SPRC is accumulating ice on flat surfaces over the years, something known as a "positive mass balance". Although during the year with the halos, the cap could have experienced negative mass balance, it promptly recovered the following year. This means that large global dust storm events, like the one that we believe produced the halos could hold the key to explaining why the SPRC continues to exist. More dust particles in the air can increase the amount of snowfall over direct condensation of carbon dioxide, causing the surface to smooth out, enabling easier accumulation in the following winter.
I am currently working on the analysis of sequences of icy layers preserved in Mars' polar caps, in search of clues that could help us form an idea of what Mars' climate was like when the caps were forming. The main bulk of Mars' polar caps are known as the Polar Layered Deposits (PLD). They are large caps a few kilometers thick, that are composed of many layers of water ice and dust that were deposited and eroded over time as Mars' climate changed due to variations in its orbit and rotation. These deposits have been cut through by large troughs and canyons, which is why the instruments on MRO can observe the layers directly. These layered walls appear similar to the walls of the Grand Canyon in Arizona, and are in fact very similar to the layers seen in ice cores taken from Earth's largest ice sheets, like Antarctica and Greenland. The goal of this project is to characterize certain properties of the layers, such as resistance to erosion, and to search for patterns in these properties that repeat over the depth of the cap. Knowing that certain types of layers repeat over depth/time, it is possible to associate these episodes of layer formation with changing Martian climates, and obtain detailed knowledge about how Mars' climate changes affected its surface and overall environment over millions of years. For this analysis I will use high resolution Digital Terrain Models, constructed from HiRISE stereo images. These 1 meter/pixel elevation maps are ideal for evaluating various properties of individual layers or small layer packets within the polar stratigraphy. Unfortunately not many DTMs have been made, especially for the South PLD, so a large part of my project includes creating DTMs like the one seen below, using specialized 3D visualization equipment. This project is funded by a NASA Earth and Space Science Fellowship, which I was awarded during my third year of graduate school.
Brown, A.J., Calvin, W.M., Becerra, P., Byrne, S. (2015). Quantification of the summertime water ice deposition on the Martian north polar ice cap. Earth and Space Science. Accepted with revisions.
Becerra, P., Byrne, S., Brown A.J. (2015). Transient Bright “Halos” on the South Polar Residual Cap of Mars: Implications for Mass Balance . Icarus (in press for the Dynamic Mars Special issue). doi: 10.1016/j.icarus.2014.04.050.
Pelletier, J. D., DeLong, S.B., Orem, C.A., Becerra, P., Compton, K., Gressett, K., Lyons-Baral, J., McGuire, L.A., Molaro, J.L., and Spinler J.C. (2012). How do vegetation bands form in dry lands? Insights from numerical modeling and field studies in southern Nevada, USA. J. Geophys. Res., 117, F04026, doi:10.1029/2012JF002465.
French, R.S., Showalter, M.R., Sfair, R., Argüelles, C., Pajuelo, M., Becerra, P., Hedman, M.M., Nicholson, P.D. (2012) “The Brightening of Saturn’s F Ring”. Icarus 219: 181-193.
I was born in Lima, Peru on July 5th, 1985. At age 10 i moved to Atlanta, GA, where i lived for 2 years with my family. After that I moved back to Peru and finished school there. In "high school" (Peru has K-12 schools), I was part of the swim team, volleyball and basketball teams (those who know me have a hard time believing the last two...let's just say I'm not the tallest guy), and I was president of my class' student council. Here I made some of the best friends I have, and I still get together with them every time I visit home. After high school, I went on to study Physics at the Pontificia Universidad Catolica del Peru (PUCP). During my time as an undergraduate i had the opportunity to study one semester as an exchange student at the University of Alberta in Edmonton, Alberta, Canada. Here i made some great friends, and learned a lot about astronomy, really cold weather, and life in general. I graduated with a B.S. in physics in 2007, and during the first year after graduation i worked as a research assistant in the Astronomy section of the Peruvian Space Agency. Also during that time i went through the tedious process of applying to graduate school for Planetary Science and was finally accepted at the University of Arizona's Lunar and Planetary Laboratory (LPL) in Tucson, Arizona.
I absolutely love travelling, so in the few months between being accepted and beginning graduate school i took a backpacking trip through Europe. I visited Madrid, Barcelona, Paris, Brussels, Bruge, Amsterdam, Prague, and finally made it to Florence, where i stayed for a month learning Italian. I made the best of my time in Florence by travelling to a different part of Italy every weekend. I even made it down to Greece. It was truly an amazing experience. More recently, I went on an awesome 3-day backpacking trip to Yosemite National Park with one of my best friends from high school. It was a great trip, made all the better by having to avoid the massive forest fire that burnt most of the southern area of the park. The smoke made the Sun appear bright red from our campsite, which was kind of a unique experience.
Here in Tucson I train for and participate in triathlons, and am part of the University of Arizona TRICATS Triathlon club. We train as a team and compete as part of the Mountain Collegiate Triathlon Conference. The club is like a family, and is one of my favorite things about being in Tucson, not to mention that during practices I get to ride around most of the city and its surrounding mountains on my bike. When I'm not working or training, i enjoy SCUBA diving, playing guitar, and going home to Lima to visit friends and family. I also practice jiu-jitsu as a hobby, and love snowboarding during the winter, although that's hard to do in Tucson most years. I love food (cooking it and eating it) and drinks, especially peruvian food and Pisco, our national drink. I always bring a bottle (or bottles) of Pisco back to Tucson everytime i go home to Lima.
Lunar and Planetary Laboratory
University of Arizona
Kuiper Space Sciences Building
1629 E. University Blvd. Of. 334
Office: 1 (520) 621-1632