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<\/figure>“An important lesson I have learned over the years is not to be afraid to ask if you hit a bump in the road or want something. You are not losing anything by just asking\u2014and trust me, many great people out there are happy to help and give you feedback.”<\/em><\/p>\n\n\n\n \u2014Haifeng Xiao<\/strong><\/p>\n<\/div><\/div>\n\n\n\n Hi, my name is Haifeng Xiao. I was born in Tianmen City in China, also home to Lu Yu, who has written the book \u201cThe Classics of Tea\u201d and is respected as \u201cthe Sage of Tea.\u201d The city is also famous for its various steamed dishes, which are mouth-watering.<\/p>\n\n\n\n Previously, I obtained my master\u2019s degree from Shanghai Tongji University<\/a>, China. I am pursuing my Ph.D. in Technische Universit\u00e4t Berlin<\/a>, Germany.<\/p>\n\n\n\n During my master’s studies, I focused on examining the evolution, for example, width, length, and depth, of large frontal fractures (approximately 50 km in length, 1.5 km in width, and 50 m in depth) within the Filchner-Ronne Ice Shelf in the Antarctic using a variety of satellite data. After drawing insights from past calving cycles, I predicted that the upcoming major calving event will occur approximately in 2051<\/a>. Witnessing the calving on-site and verifying if the timing fits our conclusion will be exciting.<\/p>\n\n\n My Ph.D. theme revolves around the Martian polar caps\u2014specifically, the seasonal carbon dioxide (CO2<\/sub>) deposits condensing onto the polar surface from the atmosphere. Due to the obliquity of its spin axis, Mars also has seasons like that on Earth. During fall and winter, the temperature can plunge below the frost point of carbon dioxide (~-125\u00b0C on average) and lead to snow and frost deposition. (For reference, the lowest natural temperature ever directly recorded at ground level on Earth is -89.2\u00b0C at the then-Soviet Vostok Station in Antarctica in 1983.)<\/p>\n\n\n\n An interesting note is that the CO2<\/sub> snow particles are about 100 times smaller than terrestrial water ice snowflakes and lack the intricate symmetry and platy structure of the Earthly snow. The Martian snowfall thus would probably look like a fog rather than resembling a blizzard.<\/p>\n\n\n\n Meanwhile, during spring and summer, the temperature rises, and the CO2<\/sub> deposits sublimate back into the atmosphere (changes from solid directly to gas). These seasonal deposition\/sublimation processes exchange up to one-third of the atmosphere\u2019s CO2<\/sub> with the polar regions through these seasonal deposition\/sublimation processes.<\/p>\n\n\n\n “This motivates my Ph.D. studies that utilized the dynamic topographic heights recorded by the Mars Orbiter Laser Altimeter onboard NASA\u2019s Mars Global Surveyor spacecraft to look into the thickness variations of the seasonal deposits.”<\/em><\/p>\n<\/div> Constraints on the amount of seasonal deposits can shed essential insights into the Martian volatile cycles. While the lateral extent of the seasonal deposits has been extensively mapped using satellite images and temperature measurements, its vertical evolution at high spatial and temporal resolution\u2014that is, at local scales\u2014has yet to be investigated.<\/p>\n\n\n\n This motivates my Ph.D. studies that utilized the dynamic topographic heights recorded by the Mars Orbiter Laser Altimeter (MOLA)<\/a> onboard NASA<\/a>\u2019s Mars Global Surveyor (MGS)<\/a> spacecraft to look into the thickness variations of the seasonal deposits.<\/p>\n\n\n\n A laser altimeter is an instrument that precisely measures the distance from an orbiting spacecraft to the planetary surface by measuring the time of travel of an emitted and then reflected laser beam; given the position and attitude of the spacecraft, the topographic heights of individual laser-illuminated footprints can be determined.<\/p>\n\n\n\n Unlike optical instruments, a laser altimeter does not require sunlight and can thus peer into the darkness at polar night. For MOLA, more than 8,000 profiles and 600 million footprints acquired from March 1999 to June 2001 are available, which span more than one full Martian year.<\/p>\n\n\n\n Previous approaches primarily relied on the height differences at the intersection points, or cross-overs, of a pair of laser ground tracks acquired at different time epochs. However, due to non-infinite sampling of the laser pulses (firing ten beams per second as of MOLA), the separation distance between consecutive footprints can be ~300 m. The Achilles heel of the cross-over approach is thus that heights at the intersections need to be interpolated from the bracketing footprints along each track, which can severely deteriorate the thickness measurements, especially when the interpolation distance is significant, and the terrain is rough.<\/p>\n\n\n\n
\n\n\n\nAt a Glance<\/h2>\n\n\n\n
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\n\n\n\nWho are you, and where are you from? Where did you study, and where do you currently study?<\/h5>\n\n\n\n
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\n\n\n\nWhat do you currently study?<\/h5>\n\n\n\n
\n\n\n\nWhy did you choose your field of study?<\/h5>\n\n\n\n
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\n\n\n\nTell us about one of your works that you are most proud of.<\/h5>\n\n\n\n
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