Context. Shock-induced changes in ordinary chondrite meteorites related to impacts or planetary c... more Context. Shock-induced changes in ordinary chondrite meteorites related to impacts or planetary collisions are known to be capable of altering their optical properties. Thus, one can hypothesize that a significant portion of the ordinary chondrite material may be hidden within the observed dark C/X asteroid population. Aims. The exact pressure-temperature conditions of the shock-induced darkening are not well constrained. Thus, we experimentally investigate the gradual changes in the chondrite material optical properties as a function of the shock pressure. Methods. A spherical shock experiment with Chelyabinsk LL5 was performed in order to study the changes in its optical properties. The spherical shock experiment geometry allows for a gradual increase of shock pressure from ~15 GPa at a rim toward hundreds of gigapascals in the center. Results. Four distinct zones were observed with an increasing shock load. The optical changes are minimal up to ~50 GPa. In the region of ~50–60 GP...
The results of retrieval tests on simulated PFS single spectra are presented. PFS is an infrared ... more The results of retrieval tests on simulated PFS single spectra are presented. PFS is an infrared Fourier spectrometer on board of Mars Express mission. It has been designed to investigate the Martian atmosphere, with special attention on CO2, dust and wa- ter vapor cycles at different time scales. A wide dataset of synthetic spectra has been computed on the basis
Several hundred spectra were obtained at latitudes > 65N in late northern winter (Ls = 322o -3... more Several hundred spectra were obtained at latitudes > 65N in late northern winter (Ls = 322o -352o ). Solar zenith angles ranged from 75o to 125o ; however, most of these spectra were obtained in polar darkness. The data reveal complex spectral features, including a complex shape in the 15mu m CO2 band. Temperature profiles and aerosol opacities were retrieved
This work presents a review of the observations acquired by the planetary Fourier spectrometer (P... more This work presents a review of the observations acquired by the planetary Fourier spectrometer (PFS) in the region of the Hellas basin. Taking advantage of the high spectral resolution of PFS, the vertical air temperature profile can be investigated with a previously ...
We have analyzed spectra of CO recorded with the instrument PFS onboard Mars Express in the (1-0)... more We have analyzed spectra of CO recorded with the instrument PFS onboard Mars Express in the (1-0) 4:7 mm band. The dataset we used ranges in time from January until June 2004 (L S ¼ 331 3 :17 until L S ¼ 51 3 :61; end of Mars Year 26, beginning of Mars Year 27). The aim of this work was to determine the amplitude of the CO mixing ratio departures from the mean globally averaged value currently admitted (873 Â 10 À4) [Kaplan, L.D., Connes, J., Connes, P., 1969. Carbon monoxide in the martian atmosphere. Astron. J. 157, L187-L192] as a function of season, local time and location on the planet. We therefore processed the data from 90 calibrated orbits. The globally averaged CO mixing ratio value we derive from our dataset, 11:1 Â 10 À4 , is compatible with the range found by Kaplan et al. [1969. Carbon monoxide in the martian atmosphere. Astron. J. 157, L187-L192], although somewhat higher than the ''standard'' value. However, the CO mixing ratio we retrieve exhibits large variations (roughly between 3 Â 10 À4 and 18 Â 10 À4). Such relative variations have been used on a statistical basis to derive main trends as a function of latitude for three L S ranges: 331-360 3 , 0-30 3 and 30-52 3. For the first L S range, we seem to have an enhancement of the CO mixing ratio towards the northern latitudes, probably linked to the CO 2 condensation in winter on the north polar cap. The situation for the two other L S ranges is not so clear, mainly as we lack data on the southern hemisphere. We roughly agree with the work of Krasnopolsky [2007. Long-term spectroscopic observations of Mars using IRTF/CSHELL: mapping of O2 dayglow, CO and search for CH4. Icarus 190, 93-102] for L S ¼ 331-360 3 , thus confirming the effect of seasonal condensation of CO 2 on the north polar cap, but we have no agreement for other seasons.
ABSTRACT We present reflectance spectra of Mercury analog materials, compare the TIR reflectance ... more ABSTRACT We present reflectance spectra of Mercury analog materials, compare the TIR reflectance spectra of the samples to their emission spectra to evaluate deviations from Kirchhoff's law, and report on a space weathering simulation experiment on feldspar.
Dark aeolian deposits on Mars are thought to consist of volcanic materials due to their mineral a... more Dark aeolian deposits on Mars are thought to consist of volcanic materials due to their mineral assemblages, which are common to basalts. However, the sediment source is still debated. Basaltic dunes on Earth are promising analogs for providing further insights into the assumed basaltic sand dunes on Mars. In our study we characterize basaltic dunes from the Ka'u Desert in Hawaii using optical microscopes, electron microprobe, and spectral analyses. We compare the spectra of terrestrial and Martian dune sands to determine possible origins of the Martian dark sediments. Our results show that the terrestrial sands consist primarily of medium to coarse sand-sized volcanic glass and rock fragments as well as olivine, pyroxene, and plagioclase minerals. Grain shapes range from angular to subrounded. The sample composition indicates that the material was derived from phreatomagmatic eruptions partially with additional proportions of rock fragments from local lava flows. Grain shape and size indicate the materials were transported by aeolian processes rather than by fluvial processes. Spectral analyses reveal an initial hydration of all terrestrial samples. A spectral mineralogical correlation between the terrestrial and Martian aeolian sands shows a similarity consistent with an origin from volcanic ash and lava. We suggest that the Martian deposits may contain similar abundances of volcanic glass, which has not yet been distinguished in Martian spectral data.
The Institute for Planetary Research has an expertise in spectroscopy of minerals, rocks, meteori... more The Institute for Planetary Research has an expertise in spectroscopy of minerals, rocks, meteorites, and organic matter, build up in more than two decades. The available equipment allows spectroscopy from the visible to TIR range using bi-conical reflection, transmission and emission spectroscopy. The institute has an outstanding heritage in designing and building infrared remote-sensing instruments for planetary missions. The PEL has been operating in various configurations for the last 10 years. The laboratory experimental facilities consist of the main emissivity spectrometer laboratory, a supporting spectrometer laboratory for reflectance and transmission measurements, sample preparation facilities and an extensive collection of rocks and minerals.
Landforms unique to Mercury, hollows are shallow, flat-floored irregular depressions notable for ... more Landforms unique to Mercury, hollows are shallow, flat-floored irregular depressions notable for their relatively high reflectance and characteristic color. Here we document the range of geological settings in which hollows occur. Most are associated with impact structures (simple bowl-shaped craters to multiring basins, and ranging from Kuiperian to Calorian in age). Hollows are found in the low-reflectance material global color unit and in low-reflectance blue plains, but they appear to be absent from high-reflectance red plains. Hollows may occur preferentially on equator-or hot-pole-facing slopes, implying that their formation is linked to solar heating. Evidence suggests that hollows form because of loss of volatile material. We describe hypotheses for the origin of the volatiles and for how such loss proceeds. Intense space weathering and solar heating are likely contributors to the loss of volatiles; contact heating by melts could promote the formation of hollows in some locations. Lunar Ina-type depressions differ from hollows on Mercury in a number of characteristics, so it is unclear if they represent a good analog. We also use MESSENGER multispectral images to characterize a variety of surfaces on Mercury, including hollows, within a framework defined by laboratory spectra for analog minerals and lunar samples. Data from MESSENGER's X-Ray Spectrometer indicate that the planet's surface contains up to 4% sulfur. We conclude that nanophase or microphase sulfide minerals could contribute to the low reflectance of the low-reflectance material relative to average surface material. Hollows may owe their relatively high reflectance to destruction of the darkening agent (sulfides), the presence of alteration minerals, and/or physical differences in particle size, texture, or scattering behavior.
Infrared Remote Sensing and Instrumentation XVIII, 2010
The Mercury Radiometer and Thermal Infrared Imaging Spectrometer MERTIS on the joint ESA-JAXA mis... more The Mercury Radiometer and Thermal Infrared Imaging Spectrometer MERTIS on the joint ESA-JAXA mission BepiColombo to Mercury is combining a spectrometer using an uncooled microbolometer in a pushbroom mode with a highly miniaturized radiometer. A full development model of MERTIS is now available. So, after three flybys of Mercury by the MESSENGER mission and with the Planetary Emissivity Laboratory at
Infrared Remote Sensing and Instrumentation XXI, 2013
ABSTRACT The permanent cloud cover of Venus prohibits observation of the surface with traditional... more ABSTRACT The permanent cloud cover of Venus prohibits observation of the surface with traditional imaging techniques most of the visible spectral range. Venus' CO2 atmosphere is transparent in small spectral windows near 1 micron. These windows have been successfully used from ground observers, during the flyby of the Galileo mission at Jupiter and most recently by the VMC and VIRTIS instruments on the ESA VenusExpress spacecraft. Studying surface composition based on only a small number of spectral channels in a very narrow spectral range is very challenging. The task is further complicated by the fact that Venus has an average surface temperature of 460°C. Spectral signatures of minerals are affected by temperature and therefore a comparison with mineral spectra obtained at room temperature can be misleading. We report here about first laboratory measurements of Venus analog materials obtained at Venus surface temperatures. The spectral signatures show clear temperature dependence. Based on the experience gained from using the VIRTIS instrument to observe the surface of Venus combined with the high temperature laboratory experiments we have developed the concept for the Venus Emissivity Mapper (VEM). VEM is a multi-spectral mapper dedicated to the task of multi-spectral mapping the surface of Venus. VEM imposes minimal requirements on the spacecraft and mission design and can therefore added to any future Venus mission. Ideally the VEM instrument is combined with a high resolution radar mapper to provide accurate topographic data.
We identify mineral types and approximate abundances on Mercury's surface from 196° to 270°W... more We identify mineral types and approximate abundances on Mercury's surface from 196° to 270°W longitude from five slit observations at regions in north-mid and north latitudes. The subtending slit sectors have central coordinates as follows: (1) 11 April 2006#89; 203°W, 13°N 205°W, 47°N (2) 7 April 2006#77; 210°W, 8°N 230°W, 25°N (3) 11 April 2006#96; 212°W, 15°N 219°W, 45°N (4) 11 April 2006#93; 225°W, 13°N 237°W, 45°N (5) 11 April 2006#109; 262°W, 8°N, 267°W, 25°N. Our results are obtained by modeling spectra obtained with the Mid-Infrared Spectrometer and Imager (MIRSI) at the Infrared Telescope Facility (IRTF) using an established spectral deconvolution algorithm (Ramsey 1996, Ph.D. Dissertation, ASU; Ramsey and Christiansen 1998, JGR). We have assembled several mineral libraries (JHU, Salisbury et al. 1991; JPL, http://speclib.jpl.nasa.gov; RELAB, http://www.planetary brown.edu/relab; ASU, http://speclib.asu.edu; BED, Maturilli et al. 2007, LPSC XXXVIII Abs.) consisting of ...
Context. Shock-induced changes in ordinary chondrite meteorites related to impacts or planetary c... more Context. Shock-induced changes in ordinary chondrite meteorites related to impacts or planetary collisions are known to be capable of altering their optical properties. Thus, one can hypothesize that a significant portion of the ordinary chondrite material may be hidden within the observed dark C/X asteroid population. Aims. The exact pressure-temperature conditions of the shock-induced darkening are not well constrained. Thus, we experimentally investigate the gradual changes in the chondrite material optical properties as a function of the shock pressure. Methods. A spherical shock experiment with Chelyabinsk LL5 was performed in order to study the changes in its optical properties. The spherical shock experiment geometry allows for a gradual increase of shock pressure from ~15 GPa at a rim toward hundreds of gigapascals in the center. Results. Four distinct zones were observed with an increasing shock load. The optical changes are minimal up to ~50 GPa. In the region of ~50–60 GP...
The results of retrieval tests on simulated PFS single spectra are presented. PFS is an infrared ... more The results of retrieval tests on simulated PFS single spectra are presented. PFS is an infrared Fourier spectrometer on board of Mars Express mission. It has been designed to investigate the Martian atmosphere, with special attention on CO2, dust and wa- ter vapor cycles at different time scales. A wide dataset of synthetic spectra has been computed on the basis
Several hundred spectra were obtained at latitudes > 65N in late northern winter (Ls = 322o -3... more Several hundred spectra were obtained at latitudes > 65N in late northern winter (Ls = 322o -352o ). Solar zenith angles ranged from 75o to 125o ; however, most of these spectra were obtained in polar darkness. The data reveal complex spectral features, including a complex shape in the 15mu m CO2 band. Temperature profiles and aerosol opacities were retrieved
This work presents a review of the observations acquired by the planetary Fourier spectrometer (P... more This work presents a review of the observations acquired by the planetary Fourier spectrometer (PFS) in the region of the Hellas basin. Taking advantage of the high spectral resolution of PFS, the vertical air temperature profile can be investigated with a previously ...
We have analyzed spectra of CO recorded with the instrument PFS onboard Mars Express in the (1-0)... more We have analyzed spectra of CO recorded with the instrument PFS onboard Mars Express in the (1-0) 4:7 mm band. The dataset we used ranges in time from January until June 2004 (L S ¼ 331 3 :17 until L S ¼ 51 3 :61; end of Mars Year 26, beginning of Mars Year 27). The aim of this work was to determine the amplitude of the CO mixing ratio departures from the mean globally averaged value currently admitted (873 Â 10 À4) [Kaplan, L.D., Connes, J., Connes, P., 1969. Carbon monoxide in the martian atmosphere. Astron. J. 157, L187-L192] as a function of season, local time and location on the planet. We therefore processed the data from 90 calibrated orbits. The globally averaged CO mixing ratio value we derive from our dataset, 11:1 Â 10 À4 , is compatible with the range found by Kaplan et al. [1969. Carbon monoxide in the martian atmosphere. Astron. J. 157, L187-L192], although somewhat higher than the ''standard'' value. However, the CO mixing ratio we retrieve exhibits large variations (roughly between 3 Â 10 À4 and 18 Â 10 À4). Such relative variations have been used on a statistical basis to derive main trends as a function of latitude for three L S ranges: 331-360 3 , 0-30 3 and 30-52 3. For the first L S range, we seem to have an enhancement of the CO mixing ratio towards the northern latitudes, probably linked to the CO 2 condensation in winter on the north polar cap. The situation for the two other L S ranges is not so clear, mainly as we lack data on the southern hemisphere. We roughly agree with the work of Krasnopolsky [2007. Long-term spectroscopic observations of Mars using IRTF/CSHELL: mapping of O2 dayglow, CO and search for CH4. Icarus 190, 93-102] for L S ¼ 331-360 3 , thus confirming the effect of seasonal condensation of CO 2 on the north polar cap, but we have no agreement for other seasons.
ABSTRACT We present reflectance spectra of Mercury analog materials, compare the TIR reflectance ... more ABSTRACT We present reflectance spectra of Mercury analog materials, compare the TIR reflectance spectra of the samples to their emission spectra to evaluate deviations from Kirchhoff's law, and report on a space weathering simulation experiment on feldspar.
Dark aeolian deposits on Mars are thought to consist of volcanic materials due to their mineral a... more Dark aeolian deposits on Mars are thought to consist of volcanic materials due to their mineral assemblages, which are common to basalts. However, the sediment source is still debated. Basaltic dunes on Earth are promising analogs for providing further insights into the assumed basaltic sand dunes on Mars. In our study we characterize basaltic dunes from the Ka'u Desert in Hawaii using optical microscopes, electron microprobe, and spectral analyses. We compare the spectra of terrestrial and Martian dune sands to determine possible origins of the Martian dark sediments. Our results show that the terrestrial sands consist primarily of medium to coarse sand-sized volcanic glass and rock fragments as well as olivine, pyroxene, and plagioclase minerals. Grain shapes range from angular to subrounded. The sample composition indicates that the material was derived from phreatomagmatic eruptions partially with additional proportions of rock fragments from local lava flows. Grain shape and size indicate the materials were transported by aeolian processes rather than by fluvial processes. Spectral analyses reveal an initial hydration of all terrestrial samples. A spectral mineralogical correlation between the terrestrial and Martian aeolian sands shows a similarity consistent with an origin from volcanic ash and lava. We suggest that the Martian deposits may contain similar abundances of volcanic glass, which has not yet been distinguished in Martian spectral data.
The Institute for Planetary Research has an expertise in spectroscopy of minerals, rocks, meteori... more The Institute for Planetary Research has an expertise in spectroscopy of minerals, rocks, meteorites, and organic matter, build up in more than two decades. The available equipment allows spectroscopy from the visible to TIR range using bi-conical reflection, transmission and emission spectroscopy. The institute has an outstanding heritage in designing and building infrared remote-sensing instruments for planetary missions. The PEL has been operating in various configurations for the last 10 years. The laboratory experimental facilities consist of the main emissivity spectrometer laboratory, a supporting spectrometer laboratory for reflectance and transmission measurements, sample preparation facilities and an extensive collection of rocks and minerals.
Landforms unique to Mercury, hollows are shallow, flat-floored irregular depressions notable for ... more Landforms unique to Mercury, hollows are shallow, flat-floored irregular depressions notable for their relatively high reflectance and characteristic color. Here we document the range of geological settings in which hollows occur. Most are associated with impact structures (simple bowl-shaped craters to multiring basins, and ranging from Kuiperian to Calorian in age). Hollows are found in the low-reflectance material global color unit and in low-reflectance blue plains, but they appear to be absent from high-reflectance red plains. Hollows may occur preferentially on equator-or hot-pole-facing slopes, implying that their formation is linked to solar heating. Evidence suggests that hollows form because of loss of volatile material. We describe hypotheses for the origin of the volatiles and for how such loss proceeds. Intense space weathering and solar heating are likely contributors to the loss of volatiles; contact heating by melts could promote the formation of hollows in some locations. Lunar Ina-type depressions differ from hollows on Mercury in a number of characteristics, so it is unclear if they represent a good analog. We also use MESSENGER multispectral images to characterize a variety of surfaces on Mercury, including hollows, within a framework defined by laboratory spectra for analog minerals and lunar samples. Data from MESSENGER's X-Ray Spectrometer indicate that the planet's surface contains up to 4% sulfur. We conclude that nanophase or microphase sulfide minerals could contribute to the low reflectance of the low-reflectance material relative to average surface material. Hollows may owe their relatively high reflectance to destruction of the darkening agent (sulfides), the presence of alteration minerals, and/or physical differences in particle size, texture, or scattering behavior.
Infrared Remote Sensing and Instrumentation XVIII, 2010
The Mercury Radiometer and Thermal Infrared Imaging Spectrometer MERTIS on the joint ESA-JAXA mis... more The Mercury Radiometer and Thermal Infrared Imaging Spectrometer MERTIS on the joint ESA-JAXA mission BepiColombo to Mercury is combining a spectrometer using an uncooled microbolometer in a pushbroom mode with a highly miniaturized radiometer. A full development model of MERTIS is now available. So, after three flybys of Mercury by the MESSENGER mission and with the Planetary Emissivity Laboratory at
Infrared Remote Sensing and Instrumentation XXI, 2013
ABSTRACT The permanent cloud cover of Venus prohibits observation of the surface with traditional... more ABSTRACT The permanent cloud cover of Venus prohibits observation of the surface with traditional imaging techniques most of the visible spectral range. Venus' CO2 atmosphere is transparent in small spectral windows near 1 micron. These windows have been successfully used from ground observers, during the flyby of the Galileo mission at Jupiter and most recently by the VMC and VIRTIS instruments on the ESA VenusExpress spacecraft. Studying surface composition based on only a small number of spectral channels in a very narrow spectral range is very challenging. The task is further complicated by the fact that Venus has an average surface temperature of 460°C. Spectral signatures of minerals are affected by temperature and therefore a comparison with mineral spectra obtained at room temperature can be misleading. We report here about first laboratory measurements of Venus analog materials obtained at Venus surface temperatures. The spectral signatures show clear temperature dependence. Based on the experience gained from using the VIRTIS instrument to observe the surface of Venus combined with the high temperature laboratory experiments we have developed the concept for the Venus Emissivity Mapper (VEM). VEM is a multi-spectral mapper dedicated to the task of multi-spectral mapping the surface of Venus. VEM imposes minimal requirements on the spacecraft and mission design and can therefore added to any future Venus mission. Ideally the VEM instrument is combined with a high resolution radar mapper to provide accurate topographic data.
We identify mineral types and approximate abundances on Mercury's surface from 196° to 270°W... more We identify mineral types and approximate abundances on Mercury's surface from 196° to 270°W longitude from five slit observations at regions in north-mid and north latitudes. The subtending slit sectors have central coordinates as follows: (1) 11 April 2006#89; 203°W, 13°N 205°W, 47°N (2) 7 April 2006#77; 210°W, 8°N 230°W, 25°N (3) 11 April 2006#96; 212°W, 15°N 219°W, 45°N (4) 11 April 2006#93; 225°W, 13°N 237°W, 45°N (5) 11 April 2006#109; 262°W, 8°N, 267°W, 25°N. Our results are obtained by modeling spectra obtained with the Mid-Infrared Spectrometer and Imager (MIRSI) at the Infrared Telescope Facility (IRTF) using an established spectral deconvolution algorithm (Ramsey 1996, Ph.D. Dissertation, ASU; Ramsey and Christiansen 1998, JGR). We have assembled several mineral libraries (JHU, Salisbury et al. 1991; JPL, http://speclib.jpl.nasa.gov; RELAB, http://www.planetary brown.edu/relab; ASU, http://speclib.asu.edu; BED, Maturilli et al. 2007, LPSC XXXVIII Abs.) consisting of ...
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