Seasonal Polar Carbon Dioxide Frost on Mars: Spatiotemporal Quantification of CO2 Utilizing 2001 Mars Odyssey Gamma Ray Spectrometer Data

Persistent Link:
http://hdl.handle.net/10150/193635
Title:
Seasonal Polar Carbon Dioxide Frost on Mars: Spatiotemporal Quantification of CO2 Utilizing 2001 Mars Odyssey Gamma Ray Spectrometer Data
Author:
Kelly, Eleanor Jane
Issue Date:
2006
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The exchange of carbon dioxide between the atmosphere and the polar caps on Mars creates a seasonal cycle of growth and retreat of the polar caps. As the major component of the Martian atmosphere, CO2 condenses in the polar regions of the planet during the winter seasons and precipitates as CO2 frost. It then sublimes during the spring and summer seasons in response to solar radiation. Through natural radioactivity or when exposed to cosmic rays, elements in the Martian near-subsurface (uppermost meter) emit gamma rays with distinct, characteristic energies. The Gamma Ray Spectrometer (GRS) onboard the 2001 Mars Odyssey satellite is used to measure the gamma rays coming from the Martian regolith to calculate elemental distributions, abundances, and temporal variations in the gamma ray flux. Changes in the CO2 frost over time can be quantified by observing attenuation effects of H (2223 keV hydrogen) and 40K (1461 keV potassium) gamma ray signals transmitted through various depths of polar CO2 overburden throughout the Martian seasons.Conclusions are drawn about the spatial extent, column density, and mass of Mars' seasonal polar caps as a function of time utilizing GRS data. Columnar thickness and mass results are discussed and plotted for latitudes including +/-60 degrees and poleward. GRS observations are compared to predictions from the NASA Ames Research Center Mars General Circulation Model (ARC GCM) and to similar experimental results from the Mars Odyssey High Energy Neutron Detector (HEND) and the Neutron Spectrometer (NS). Models for north and south polar atmosphere and regolith distributions are incorporated, and the results indicate that the assumption of a 100% H2O-ice residual cap underlying the seasonal frost in the north is accurate. The GRS CO2 frost observations are in good agreement with the other studies mentioned, in particular for the timing of the beginning of frost deposition to the complete sublimation of surface CO2 back into the atmosphere. The total amount of condensed CO2 mass derived from GRS data is on the order of 6.0 x 10^15 kg and verifies previous reports that ~25% of the total Martian exchangeable-CO2 reservoir participates in the ground-atmosphere cycle.
Type:
text; Electronic Dissertation
Keywords:
Mars; carbon dioxide; CO2; polar caps
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Physics; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Boynton, William V; Rutherfoord, John P

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleSeasonal Polar Carbon Dioxide Frost on Mars: Spatiotemporal Quantification of CO2 Utilizing 2001 Mars Odyssey Gamma Ray Spectrometer Dataen_US
dc.creatorKelly, Eleanor Janeen_US
dc.contributor.authorKelly, Eleanor Janeen_US
dc.date.issued2006en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe exchange of carbon dioxide between the atmosphere and the polar caps on Mars creates a seasonal cycle of growth and retreat of the polar caps. As the major component of the Martian atmosphere, CO2 condenses in the polar regions of the planet during the winter seasons and precipitates as CO2 frost. It then sublimes during the spring and summer seasons in response to solar radiation. Through natural radioactivity or when exposed to cosmic rays, elements in the Martian near-subsurface (uppermost meter) emit gamma rays with distinct, characteristic energies. The Gamma Ray Spectrometer (GRS) onboard the 2001 Mars Odyssey satellite is used to measure the gamma rays coming from the Martian regolith to calculate elemental distributions, abundances, and temporal variations in the gamma ray flux. Changes in the CO2 frost over time can be quantified by observing attenuation effects of H (2223 keV hydrogen) and 40K (1461 keV potassium) gamma ray signals transmitted through various depths of polar CO2 overburden throughout the Martian seasons.Conclusions are drawn about the spatial extent, column density, and mass of Mars' seasonal polar caps as a function of time utilizing GRS data. Columnar thickness and mass results are discussed and plotted for latitudes including +/-60 degrees and poleward. GRS observations are compared to predictions from the NASA Ames Research Center Mars General Circulation Model (ARC GCM) and to similar experimental results from the Mars Odyssey High Energy Neutron Detector (HEND) and the Neutron Spectrometer (NS). Models for north and south polar atmosphere and regolith distributions are incorporated, and the results indicate that the assumption of a 100% H2O-ice residual cap underlying the seasonal frost in the north is accurate. The GRS CO2 frost observations are in good agreement with the other studies mentioned, in particular for the timing of the beginning of frost deposition to the complete sublimation of surface CO2 back into the atmosphere. The total amount of condensed CO2 mass derived from GRS data is on the order of 6.0 x 10^15 kg and verifies previous reports that ~25% of the total Martian exchangeable-CO2 reservoir participates in the ground-atmosphere cycle.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectMarsen_US
dc.subjectcarbon dioxideen_US
dc.subjectCO2en_US
dc.subjectpolar capsen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplinePhysicsen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairBoynton, William Ven_US
dc.contributor.chairRutherfoord, John Pen_US
dc.contributor.committeememberHsieh, Ke Chiangen_US
dc.contributor.committeememberShupe, Michael A.en_US
dc.contributor.committeememberSprague, Ann L.en_US
dc.identifier.proquest1476en_US
dc.identifier.oclc137356944en_US
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