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34 results on '"Holsclaw, G. M."'

1. Martian water loss to space enhanced by regional dust storms

Author

Chaffin, M. S., Kass, D. M., Aoki, S., Fedorova, A. A., Deighan, J., Connour, K., Heavens, N. G., Kleinböhl, A., Jain, S. K., Chaufray, J.-Y., Mayyasi, M., Clarke, J. T., Stewart, A. I. F., Evans, J. S., Stevens, M. H., McClintock, W. E., Crismani, M. M. J., Holsclaw, G. M., Lefevre, F., Lo, D. Y., Montmessin, F., Schneider, N. M., Jakosky, B., Villanueva, G., Liuzzi, G., Daerden, F., Thomas, I. R., Lopez-Moreno, J.-J., Patel, M. R., Bellucci, G., Ristic, B., Erwin, J. T., Vandaele, A. C., Trokhimovskiy, A., and Korablev, O. I.

Published
2021
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2. Discovery of a proton aurora at Mars

Author

Deighan, J., Jain, S. K., Chaffin, M. S., Fang, X., Halekas, J. S., Clarke, J. T., Schneider, N. M., Stewart, A. I. F., Chaufray, J.-Y., Evans, J. S., Stevens, M. H., Mayyasi, M., Stiepen, A., Crismani, M., McClintock, W. E., Holsclaw, G. M., Lo, D. Y., Montmessin, F., Lefèvre, F., and Jakosky, B. M.

Published
2018
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3. Discovery of diffuse aurora on Mars

Author

Schneider, N. M., Deighan, J. I., Jain, S. K., Stiepen, A., Stewart, A. I. F., Larson, D., Mitchell, D. L., Mazelle, C., Lee, C. O., Lillis, R. J., Evans, J. S., Brain, D., Stevens, M. H., McClintock, W. E., Chaffin, M. S., Crismani, M., Holsclaw, G. M., Lefevre, F., Lo, D. Y., Clarke, J. T., Montmessin, F., and Jakosky, B. M.

Published
2015

4. Comparison of Newly Acquired Lunar Spectra with the Titanium Abundance Maps Derived from Clementine

Author

Holsclaw, G. M, McClintock, W. E, and Robinson, M. S

Subjects
Lunar And Planetary Science And Exploration
Abstract

The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) is one of seven science instruments onboard NASA's MESSENGER mission, currently en-route to the planet Mercury. One of MASCS s components, referred to as the Visible and Near Infrared Spectrograph (VIRS), will record reflectance spectra of the surface in order to characterize the mineralogy of the planet [1]. The lunar highlands and the average mercurian crust are proposed to be compositionally similar [i.e. 2]. In preparation to interpret VIRS reflectance spectra of Mercury to be first obtained in 2008, the Moon has been observed with an engineering model of the VIRS from a ground-based telescope. In this study, the ultraviolet and visible region of the spectrum is compared with titanium content in the lunar regolith.

Published
2005

6. Martian Thermospheric Response to an X8.2 Solar Flare on 10 September 2017 as Seen by MAVEN/IUVS

Author

Jain, S. K., primary, Deighan, J., additional, Schneider, N. M., additional, Stewart, A. I. F., additional, Evans, J. S., additional, Thiemann, E. M. B., additional, Chaffin, M. S., additional, Crismani, M., additional, Stevens, M. H., additional, Elrod, M. K., additional, Stiepen, A., additional, McClintock, W. E., additional, Lo, D. Y., additional, Clarke, J. T., additional, Eparvier, F. G., additional, Lefévre, F., additional, Montmessin, F., additional, Holsclaw, G. M., additional, Chamberlin, P. C., additional, and Jakosky, B. M., additional

Published
2018
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7. Global Aurora on Mars During the September 2017 Space Weather Event

Author

Schneider, N. M., primary, Jain, S. K., additional, Deighan, J., additional, Nasr, C. R., additional, Brain, D. A., additional, Larson, D., additional, Lillis, R., additional, Rahmati, Ali, additional, Halekas, J. S., additional, Lee, C. O., additional, Chaffin, M. S., additional, Stiepen, A., additional, Crismani, M., additional, Evans, J. S., additional, Stevens, M. H., additional, Lo, D. Y., additional, McClintock, W. E., additional, Stewart, A. I. F., additional, Yelle, R. V., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Lefevre, F., additional, Montmessin, F., additional, and Jakosky, B. M., additional

Published
2018
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8. Mars H Escape Rates Derived From MAVEN/IUVS Lyman Alpha Brightness Measurements and Their Dependence on Model Assumptions

Author

Chaffin, M. S., primary, Chaufray, J. Y., additional, Deighan, J., additional, Schneider, N. M., additional, Mayyasi, M., additional, Clarke, J. T., additional, Thiemann, E., additional, Jain, S. K., additional, Crismani, M. M. J., additional, Stiepen, A., additional, Eparvier, F. G., additional, McClintock, W. E., additional, Stewart, A. I. F., additional, Holsclaw, G. M., additional, Montmessin, F., additional, and Jakosky, B. M., additional

Published
2018
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10. Martian mesospheric cloud observations by IUVS on MAVEN: Thermal tides coupled to the upper atmosphere

Author

Stevens, M. H., primary, Siskind, D. E., additional, Evans, J. S., additional, Jain, S. K., additional, Schneider, N. M., additional, Deighan, J., additional, Stewart, A. I. F., additional, Crismani, M., additional, Stiepen, A., additional, Chaffin, M. S., additional, McClintock, W. E., additional, Holsclaw, G. M., additional, Lefèvre, F., additional, Lo, D. Y., additional, Clarke, J. T., additional, Montmessin, F., additional, and Jakosky, B. M., additional

Published
2017
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11. Detection of a persistent meteoric metal layer in the Martian atmosphere

Author

Crismani, M. M. J., primary, Schneider, N. M., additional, Plane, J. M. C., additional, Evans, J. S., additional, Jain, S. K., additional, Chaffin, M. S., additional, Carrillo-Sanchez, J. D., additional, Deighan, J. I., additional, Yelle, R. V., additional, Stewart, A. I. F., additional, McClintock, W., additional, Clarke, J., additional, Holsclaw, G. M., additional, Stiepen, A., additional, Montmessin, F., additional, and Jakosky, B. M., additional

Published
2017
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12. Nitric oxide nightglow and Martian mesospheric circulation from MAVEN/IUVS observations and LMD‐MGCM predictions

Author

Stiepen, A., primary, Jain, S. K., additional, Schneider, N. M., additional, Deighan, J. I., additional, González‐Galindo, F., additional, Gérard, J.‐C., additional, Milby, Z., additional, Stevens, M. H., additional, Bougher, S., additional, Evans, J. S., additional, Stewart, A. I. F., additional, Chaffin, M. S., additional, Crismani, M., additional, McClintock, W. E., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Montmessin, F., additional, Lefèvre, F., additional, Forget, F., additional, Lo, D. Y., additional, Hubert, B., additional, and Jakosky, B. M., additional

Published
2017
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13. Variability of D and H in the Martian upper atmosphere observed with the MAVEN IUVS echelle channel

Author

Clarke, J. T., primary, Mayyasi, M., additional, Bhattacharyya, D., additional, Schneider, N. M., additional, McClintock, W. E., additional, Deighan, J. I., additional, Stewart, A. I. F., additional, Chaufray, J.‐Y., additional, Chaffin, M. S., additional, Jain, S. K., additional, Stiepen, A., additional, Crismani, M., additional, Holsclaw, G. M., additional, Montmessin, F., additional, and Jakosky, B. M., additional

Published
2017
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14. UV Study of the Fourth Positive Band System of CO and O i 135.6 nm From Electron Impact on CO and CO2.

Author

Ajello, J. M., Malone, C. P., Evans, J. S., Holsclaw, G. M., Hoskins, A. C., Jain, S. K., McClintock, W. E., Liu, X., Veibell, V., Deighan, J., Gérard, J.‐C., Lo, D. Y., and Schneider, N.

Subjects
ELECTRONIC excitation, NANOPARTICLES, CARBON dioxide, CARBON compounds, PHOTOLUMINESCENCE, LUMINESCENCE
Abstract

We have measured the 30 and 100 eV far ultraviolet (FUV) emission cross sections of the optically allowed Fourth Positive Group (4PG) band system (A1Π → X1Σ+) of CO and the optically forbidden O (5So → 3P) 135.6 nm atomic transition by electron‐impact‐induced‐fluorescence of CO and CO2. We present a model excitation cross section from threshold to high energy for the A1Π state, including cascade by electron impact on CO. The A1Π state is perturbed by triplet states leading to an extended FUV glow from electron excitation of CO. We derive a model FUV spectrum of the 4PG band system from dissociative excitation of CO2, an important process observed on Mars and Venus. Our unique experimental setup consists of a large vacuum chamber housing an electron gun system and the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission Imaging Ultraviolet Spectrograph optical engineering unit, operating in the FUV (110–170 nm). The determination of the total O i (5So) at 135.6 nm emission cross section is accomplished by measuring the cylindrical glow pattern of the metastable emission from electron impact by imaging the glow intensity about the electron beam from nominally zero to ~400 mm distance from the electron beam. The study of the glow pattern of O i (135.6 nm) from dissociative excitation of CO and CO2 indicates that the O i (5So) state has a kinetic energy of ~1 eV by modeling the radial glow pattern with the published lifetime of 180 μs for the O i (5So) state. Plain Language Summary: Both Mars and Venus have upper atmospheres that are similar in composition: mostly CO2, CO, and N2 are dominant molecular gases, with nearly identical UV spectra. The modeling studies of atmospheric UV emissions cannot presently be accurately conducted to the same accuracy as the planetary UV measurements, which avail themselves with state‐of‐the‐art calibrated spectrographs. This dichotomy in accuracy between planetary observation and model occurs because the atomic and molecular emission cross sections with uncertainties of certain transitions are greater than 100%. Furthermore, the analysis is complicated by the spectral blending of the various emissions of the low‐resolution spectral spaceborne instruments. We present in this paper a UV laboratory instrument unique in the world at the University of Colorado that can measure for the first time the excitation mechanisms with accurate emission cross sections of both allowed and optically forbidden transitions that are occurring in a planetary atmosphere. Key Points: We measured 30 and 100 eV emission cross sections of Fourth Positive band system of CO and O i (135.6 nm) from electron impact on CO and CO2We conducted a laboratory experiment measuring single‐scattering electron‐impact‐induced‐fluorescence FUV spectra from excitation of CO and CO2Fragment kinetic energy measurement for O i (5So) atoms found to be around ~1 eV from both CO and CO2 molecular dissociation [ABSTRACT FROM AUTHOR]

Published
2019
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16. UV Study of the Fourth Positive Band System of CO and O i135.6 nm From Electron Impact on CO and CO2

Author

Ajello, J. M., Malone, C. P., Evans, J. S., Holsclaw, G. M., Hoskins, A. C., Jain, S. K., McClintock, W. E., Liu, X., Veibell, V., Deighan, J., Gérard, J.‐C., Lo, D. Y., and Schneider, N.

Abstract

We have measured the 30 and 100 eV far ultraviolet (FUV) emission cross sections of the optically allowed Fourth Positive Group (4PG) band system (A1Π → X1Σ+) of CO and the optically forbidden O (5So→ 3P) 135.6 nm atomic transition by electron‐impact‐induced‐fluorescence of CO and CO2. We present a model excitation cross section from threshold to high energy for the A1Π state, including cascade by electron impact on CO. The A1Π state is perturbed by triplet states leading to an extended FUV glow from electron excitation of CO. We derive a model FUV spectrum of the 4PG band system from dissociative excitation of CO2, an important process observed on Mars and Venus. Our unique experimental setup consists of a large vacuum chamber housing an electron gun system and the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission Imaging Ultraviolet Spectrograph optical engineering unit, operating in the FUV (110–170 nm). The determination of the total O i(5So) at 135.6 nm emission cross section is accomplished by measuring the cylindrical glow pattern of the metastable emission from electron impact by imaging the glow intensity about the electron beam from nominally zero to ~400 mm distance from the electron beam. The study of the glow pattern of O i(135.6 nm) from dissociative excitation of CO and CO2indicates that the O i(5So) state has a kinetic energy of ~1 eV by modeling the radial glow pattern with the published lifetime of 180 μs for the O i(5So) state. Both Mars and Venus have upper atmospheres that are similar in composition: mostly CO2, CO, and N2are dominant molecular gases, with nearly identical UV spectra. The modeling studies of atmospheric UV emissions cannot presently be accurately conducted to the same accuracy as the planetary UV measurements, which avail themselves with state‐of‐the‐art calibrated spectrographs. This dichotomy in accuracy between planetary observation and model occurs because the atomic and molecular emission cross sections with uncertainties of certain transitions are greater than 100%. Furthermore, the analysis is complicated by the spectral blending of the various emissions of the low‐resolution spectral spaceborne instruments. We present in this paper a UV laboratory instrument unique in the world at the University of Colorado that can measure for the first time the excitation mechanisms with accurate emission cross sections of both allowed and optically forbidden transitions that are occurring in a planetary atmosphere. We measured 30 and 100 eV emission cross sections of Fourth Positive band system of CO and O i(135.6 nm) from electron impact on CO and CO2We conducted a laboratory experiment measuring single‐scattering electron‐impact‐induced‐fluorescence FUV spectra from excitation of CO and CO2Fragment kinetic energy measurement for O i(5So) atoms found to be around ~1 eV from both CO and CO2molecular dissociation

Published
2019
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18. Global classification of MESSENGER spectral reflectance data and lab spectra comparison

Author

D'Amore, Mario, Helbert, Jörn, Maturilli, Alessandro, Head, J.W., Sprague, A. L., Izenberg, N. R., Holsclaw, G. M., McClintock, W. E., Vilas, F., and Solomon, S.C.

Subjects
MESSENGER Mercury, Experimentelle Planetenphysik
Abstract

The MESSENGER spacecraft continues to provide new data that change our views on the nature of Mercury’s surface. Assuming that surface composition can be derived from spectral reflectance measurements with the use of statistical techniques, we have employed unsupervised hierarchical clustering analyses to identify spectral units from MESSENGER’s Mercury Atmospheric and Surface Composition Spectrometer (MASCS) observations. To retrieve the number and spectral shapes of the different components present in the dataset, we collected all MASCS observations to date (> 1.5 milion spectra). Because there are no photometric corrections for MASCS available yet, the data were normalized to the reflectance level at 700 nm, yielding a ratio nearly independent of incidence and emission angles. Independent tests on laboratory data show that this approach is effective in reducing phase angle variations. The data were then interpolated to a fixed spatial grid, averaging the sub-pixel spectra. The product is a map of reflectance ratio, along with error and frequency maps to address potential error in the process and to assess reliability. This is the first global geographically registered cube-image of averaged MASCS spectra. We produced a spatial grid resolution between 4 pixels per degree (ppd) for global analyses and 0.5 ppd for regional studies. The unsupervised hierarchical clustering of the global MASCS cube-image produces a tree of data partition, starting from two mega-regions. The first mega-region (MR1) comprises equatorial to mid-latitudes and the second (MR2) the two poles. The boundaries of MR2 at high northern latitudes approximate those of the volcanic northern plains. MR2 areas show redder MASCS spectra than do MR1 areas. The spectral units show some correlation with surface units mapped by visible image acquired by MESSENGER and documented the presence of distinct spectral units on Mercury, as characterized by MASCS observations.Moreover, it seems to closely match some Gamma Ray Spectrometer elemental abudances results and global distribution of pyroclastic geological features. Following iteration produces finer separation of the surface in smaller regions. Each region average spectra is compared with reflectance spectra collected at the Berlin PEL laboratory. Here the angular dependency is treated as in the MASCS data, via normalization at 700nm. This allow us to start a geological and geochemical interpretations of MASCS observations. The materials selected aim to explore the analogs for Hollow-Forming Material on Mercury theory in : a komatiitic substrate with superimposed sulfides layer, due flotation in melted lava during volcanic eruption. We used komatiite spectra from PEL sample collection and various Mg-, Ca- and Mn- bearing sulfides. both at low and high temperature to explore the thermal schok effect on sulfide volatilization and on komatiitic substrate.

Published
2012

19. Probing the Martian atmosphere with MAVEN/IUVS stellar occultations

Author

Gröller, H., primary, Yelle, R. V., additional, Koskinen, T. T., additional, Montmessin, F., additional, Lacombe, G., additional, Schneider, N. M., additional, Deighan, J., additional, Stewart, A. I. F., additional, Jain, S. K., additional, Chaffin, M. S., additional, Crismani, M. M. J., additional, Stiepen, A., additional, Lefèvre, F., additional, McClintock, W. E., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Mahaffy, P. R., additional, Bougher, S. W., additional, and Jakosky, B. M., additional

Published
2015
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20. The structure and variability of Mars upper atmosphere as seen in MAVEN/IUVS dayglow observations

Author

Jain, S. K., primary, Stewart, A. I. F., additional, Schneider, N. M., additional, Deighan, J., additional, Stiepen, A., additional, Evans, J. S., additional, Stevens, M. H., additional, Chaffin, M. S., additional, Crismani, M., additional, McClintock, W. E., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Lo, D. Y., additional, Lefèvre, F., additional, Montmessin, F., additional, Thiemann, E. M. B., additional, Eparvier, F., additional, and Jakosky, B. M., additional

Published
2015
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21. Retrieval of CO2 and N2 in the Martian thermosphere using dayglow observations by IUVS on MAVEN

Author

Evans, J. S., primary, Stevens, M. H., additional, Lumpe, J. D., additional, Schneider, N. M., additional, Stewart, A. I. F., additional, Deighan, J., additional, Jain, S. K., additional, Chaffin, M. S., additional, Crismani, M., additional, Stiepen, A., additional, McClintock, W. E., additional, Holsclaw, G. M., additional, Lefèvre, F., additional, Lo, D. Y., additional, Clarke, J. T., additional, Eparvier, F. G., additional, Thiemann, E. M. B., additional, Chamberlin, P. C., additional, Bougher, S. W., additional, Bell, J. M., additional, and Jakosky, B. M., additional

Published
2015
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22. Three‐dimensional structure in the Mars H corona revealed by IUVS on MAVEN

Author

Chaffin, M. S., primary, Chaufray, J. Y., additional, Deighan, J., additional, Schneider, N. M., additional, McClintock, W. E., additional, Stewart, A. I. F., additional, Thiemann, E., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Jain, S. K., additional, Crismani, M. M. J., additional, Stiepen, A., additional, Montmessin, F., additional, Eparvier, F. G., additional, Chamberlain, P. C., additional, and Jakosky, B. M., additional

Published
2015
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23. Study of the Martian cold oxygen corona from the O I 130.4 nm by IUVS/MAVEN

Author

Chaufray, J. Y., primary, Deighan, J., additional, Chaffin, M. S., additional, Schneider, N. M., additional, McClintock, W. E., additional, Stewart, A. I. F., additional, Jain, S. K., additional, Crismani, M., additional, Stiepen, A., additional, Holsclaw, G. M., additional, Clarke, J. T., additional, Montmessin, F., additional, Eparvier, F. G., additional, Thiemann, E. M. B., additional, Chamberlin, P. C., additional, and Jakosky, B. M., additional

Published
2015
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24. New observations of molecular nitrogen in the Martian upper atmosphere by IUVS on MAVEN

Author

Stevens, M. H., primary, Evans, J. S., additional, Schneider, N. M., additional, Stewart, A. I. F., additional, Deighan, J., additional, Jain, S. K., additional, Crismani, M., additional, Stiepen, A., additional, Chaffin, M. S., additional, McClintock, W. E., additional, Holsclaw, G. M., additional, Lefèvre, F., additional, Lo, D. Y., additional, Clarke, J. T., additional, Montmessin, F., additional, Bougher, S. W., additional, and Jakosky, B. M., additional

Published
2015
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25. MAVEN IUVS observation of the hot oxygen corona at Mars

Author

Deighan, J., primary, Chaffin, M. S., additional, Chaufray, J.‐Y., additional, Stewart, A. I. F., additional, Schneider, N. M., additional, Jain, S. K., additional, Stiepen, A., additional, Crismani, M., additional, McClintock, W. E., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Montmessin, F., additional, Eparvier, F. G., additional, Thiemann, E. M. B., additional, Chamberlin, P. C., additional, and Jakosky, B. M., additional

Published
2015
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26. MAVEN IUVS observations of the aftermath of the Comet Siding Spring meteor shower on Mars

Author

Schneider, N. M., primary, Deighan, J. I., additional, Stewart, A. I. F., additional, McClintock, W. E., additional, Jain, S. K., additional, Chaffin, M. S., additional, Stiepen, A., additional, Crismani, M., additional, Plane, J. M. C., additional, Carrillo‐Sánchez, J. D., additional, Evans, J. S., additional, Stevens, M. H., additional, Yelle, R. V., additional, Clarke, J. T., additional, Holsclaw, G. M., additional, Montmessin, F., additional, and Jakosky, B. M., additional

Published
2015
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28. Electron impact study of the 100 eV emission cross section and lifetime of the Lyman‐Birge‐Hopfield band system of N2: Direct excitation and cascade

Author

Ajello, J. M., Malone, C. P., Holsclaw, G. M., Hoskins, A. C., Eastes, R. W., McClintock, W. E., and Johnson, P. V.

Abstract

We have measured the 100 eV emission cross section of the optically forbidden Lyman‐Birge‐Hopfield (LBH) band system (a1Πg→ X1Σ+g) of N2by electron‐impact‐induced fluorescence. Using a large (1.5 m diameter) vacuum chamber housing an electron gun system and the Mars Atmosphere and Volatile EvolutioN mission Imaging Ultraviolet Spectrograph optical engineering model, we have obtained calibrated spectral measurements of the LBH band system from 115 to 175 nm over a range of lines of sight to capture all of the optical emissions. These measurements represent the first experiment to directly isolate in the laboratory single‐scattering electron‐impact‐induced fluorescence from both direct excitation of the a1Πgstate and cascading contributions to the a1Πgstate (a′1Σ−uand w1Δu→ a1Πg→ X1Σ+g). The determination of the total LBH emission cross section is accomplished by measuring the entire cylindrical glow pattern of the metastable emission from electron impact by imaging lines of sight that measure the glow intensity from zero to ~400 mm radial distance and calculating the ratio of the integrated intensity from the LBH glow pattern to that of a simultaneously observed optically allowed transition with a well‐established cross section: Ni120.0 nm. The “direct” emission cross section of the a1Πgstate at 100 eV was determined to be σemdir= (6.41 ± 1.3) × 10−18cm2. An important observation from the glow pattern behavior is that the total (direct + cascading) emission cross section is pressure dependent due to collision‐induced cascade transitions between close‐lying electronic states. Measured 100 eV total emission cross section of the optically forbidden Lyman‐Birge‐Hopfield (LBH) band system of N2by electron‐impact‐induced fluorescenceLaboratory experiment isolating single‐scattering electron‐impact‐induced fluorescence from direct excitation and cascading contributions to the a1Πgstate of N2Lifetime for the optically forbidden a1Πgstate is found to be ~50 ± 15 μs

Published
2017
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31. Retrieval of CO2and N2in the Martian thermosphere using dayglow observations by IUVS on MAVEN

Author

Evans, J. S., Stevens, M. H., Lumpe, J. D., Schneider, N. M., Stewart, A. I. F., Deighan, J., Jain, S. K., Chaffin, M. S., Crismani, M., Stiepen, A., McClintock, W. E., Holsclaw, G. M., Lefèvre, F., Lo, D. Y., Clarke, J. T., Eparvier, F. G., Thiemann, E. M. B., Chamberlin, P. C., Bougher, S. W., Bell, J. M., and Jakosky, B. M.

Abstract

We present direct number density retrievals of carbon dioxide (CO2) and molecular nitrogen (N2) for the upper atmosphere of Mars using limb scan observations during October and November 2014 by the Imaging Ultraviolet Spectrograph on board NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. We use retrieved CO2densities to derive temperature variability between 170 and 220 km. Analysis of the data shows (1) low‐mid latitude northern hemisphere CO2densities at 170 km vary by a factor of about 2.5, (2) on average, the N2/CO2increases from 0.042 ± 0.017 at 130 km to 0.12 ± 0.06 at 200 km, and (3) the mean upper atmospheric temperature is 324 ± 22 K for local times near 14:00. Retrieved CO2densities at 170 km vary by a factor of about 2.5On average, N2/CO2increases from 4% at 130 km to 12% at 200 kmMean Martian upper atmospheric temperature over the sampled time frame is 324 {±} 22 K

Published
2015
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32. ENCELADUS: USING UV DATA TO STUDY PLUME FALLOUT.

Author

Hendrix, A. R., Hansen, C. J., Royer, E. M., Cassidy, T. A., Esposito, L. W., and Holsclaw, G. M.

Subjects
ENCELADUS (Satellite), SATELLITES of Saturn, SPACE exploration
Published
2017

33. Martian water loss to space enhanced by regional dust storms

Author

Chaffin, M. S., Kass, D. M., Aoki, S., Fedorova, A. A., Deighan, J., Connour, K., Heavens, N. G., Kleinböhl, A., Jain, S. K., Chaufray, J.-Y., Mayyasi, M., Clarke, J. T., Stewart, A. I. F., Evans, J. S., Stevens, M. H., McClintock, W. E., Crismani, M. M. J., Holsclaw, G. M., Lefevre, F., Lo, D. Y., Montmessin, F., Schneider, N. M., Jakosky, B., Villanueva, G., Liuzzi, G., Daerden, F., Thomas, I. R., Lopez-Moreno, J.-J., Patel, M.R., Bellucci, G., Ristic, B., Erwin, J. T., Vandaele, A. C., Trokhimovskiy, A., Korablev, O. I., Chaffin, M. S., Kass, D. M., Aoki, S., Fedorova, A. A., Deighan, J., Connour, K., Heavens, N. G., Kleinböhl, A., Jain, S. K., Chaufray, J.-Y., Mayyasi, M., Clarke, J. T., Stewart, A. I. F., Evans, J. S., Stevens, M. H., McClintock, W. E., Crismani, M. M. J., Holsclaw, G. M., Lefevre, F., Lo, D. Y., Montmessin, F., Schneider, N. M., Jakosky, B., Villanueva, G., Liuzzi, G., Daerden, F., Thomas, I. R., Lopez-Moreno, J.-J., Patel, M.R., Bellucci, G., Ristic, B., Erwin, J. T., Vandaele, A. C., Trokhimovskiy, A., and Korablev, O. I.

Abstract

Mars has lost most of its initial water to space as atomic hydrogen and oxygen. Spacecraft measurements have determined that present-day hydrogen escape undergoes large variations with season that are inconsistent with long-standing explanations. The cause is incompletely understood, with likely contributions from seasonal changes in atmospheric circulation, dust activity and solar extreme ultraviolet input. Although some modelling and indirect observational evidence suggest that dust activity can explain the seasonal trend, no previous study has been able to unambiguously distinguish seasonal from dust-driven forcing. Here we present synoptic measurements of dust, temperature, ice, water and hydrogen on Mars during a regional dust event, demonstrating that individual dust events can boost planetary H loss by a factor of five to ten. This regional storm occurred in the declining phase of the known seasonal trend, establishing that dust forcing can override this trend to drive enhanced escape. Because similar regional storms occur in most Mars years, these storms may be responsible for a large fraction of Martian water loss and represent an important driver of Mars atmospheric evolution.

34. Martian water loss to space enhanced by regional dust storms

Author

Chaffin, M. S., Kass, D. M., Aoki, S., Fedorova, A. A., Deighan, J., Connour, K., Heavens, N. G., Kleinböhl, A., Jain, S. K., Chaufray, J.-Y., Mayyasi, M., Clarke, J. T., Stewart, A. I. F., Evans, J. S., Stevens, M. H., McClintock, W. E., Crismani, M. M. J., Holsclaw, G. M., Lefevre, F., Lo, D. Y., Montmessin, F., Schneider, N. M., Jakosky, B., Villanueva, G., Liuzzi, G., Daerden, F., Thomas, I. R., Lopez-Moreno, J.-J., Patel, M.R., Bellucci, G., Ristic, B., Erwin, J. T., Vandaele, A. C., Trokhimovskiy, A., Korablev, O. I., Chaffin, M. S., Kass, D. M., Aoki, S., Fedorova, A. A., Deighan, J., Connour, K., Heavens, N. G., Kleinböhl, A., Jain, S. K., Chaufray, J.-Y., Mayyasi, M., Clarke, J. T., Stewart, A. I. F., Evans, J. S., Stevens, M. H., McClintock, W. E., Crismani, M. M. J., Holsclaw, G. M., Lefevre, F., Lo, D. Y., Montmessin, F., Schneider, N. M., Jakosky, B., Villanueva, G., Liuzzi, G., Daerden, F., Thomas, I. R., Lopez-Moreno, J.-J., Patel, M.R., Bellucci, G., Ristic, B., Erwin, J. T., Vandaele, A. C., Trokhimovskiy, A., and Korablev, O. I.

Abstract

Mars has lost most of its initial water to space as atomic hydrogen and oxygen. Spacecraft measurements have determined that present-day hydrogen escape undergoes large variations with season that are inconsistent with long-standing explanations. The cause is incompletely understood, with likely contributions from seasonal changes in atmospheric circulation, dust activity and solar extreme ultraviolet input. Although some modelling and indirect observational evidence suggest that dust activity can explain the seasonal trend, no previous study has been able to unambiguously distinguish seasonal from dust-driven forcing. Here we present synoptic measurements of dust, temperature, ice, water and hydrogen on Mars during a regional dust event, demonstrating that individual dust events can boost planetary H loss by a factor of five to ten. This regional storm occurred in the declining phase of the known seasonal trend, establishing that dust forcing can override this trend to drive enhanced escape. Because similar regional storms occur in most Mars years, these storms may be responsible for a large fraction of Martian water loss and represent an important driver of Mars atmospheric evolution.

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