Reddy V.,University of North Dakota |
Reddy V.,Max Planck Institute for Solar System Research |
Sanchez J.A.,Max Planck Institute for Solar System Research |
Sanchez J.A.,Institute For Planetologie |
And 10 more authors.
Icarus | Year: 2012
Phase angle and temperature are two important parameters that affect the photometric and spectral behavior of planetary surfaces in telescopic and spacecraft data. We have derived photometric and spectral phase functions for the Asteroid 4 Vesta, the first target of the Dawn mission, using ground-based telescopes operating at visible and near-infrared wavelengths (0.4-2.5μm). Photometric lightcurve observations of Vesta were conducted on 15 nights at a phase angle range of 3.8-25.7° using duplicates of the seven narrowband Dawn Framing Camera filters (0.4-1.0μm). Rotationally resolved visible (0.4-0.7μm) and near-IR spectral observations (0.7-2.5μm) were obtained on four nights over a similar phase angle range. Our Vesta photometric observations suggest the phase slope is between 0.019 and 0.029. mag/deg. The G parameter ranges from 0.22 to 0.37 consistent with previous results (e.g., Lagerkvist, C.-I., Magnusson, P., Williams, I.P., Buontempo, M.E., Argyle, R.W., Morrison, L.V. . Astron. Astrophys. Suppl. Ser. 94, 43-71; Piironen, J., Magnusson, P., Lagerkvist, C.-I., Williams, I.P., Buontempo, M.E., Morrison, L.V. . Astron. Astrophys. Suppl. Ser. 121, 489-497; Hasegawa, S. et al. . Lunar Planet. Sci. 40. ID 1503) within the uncertainty. We found that in the phase angle range of 0°<.α≤. 25° for every 10° increase in phase angle Vesta's visible slope (0.5-0.7μm) increases 20%, Band I and Band II depths increase 2.35% and 1.5% respectively, and the BAR value increase 0.30. Phase angle spectral measurements of the eucrite Moama in the lab show a decrease in Band I and Band II depths and BAR from the lowest phase angle 13° to 30°, followed by possible small increases up to 90°, and then a dramatic drop between 90° and 120° phase angle. Temperature-induced spectral effects shift the Band I and II centers of the pyroxene bands to longer wavelengths with increasing temperature. We have derived new correction equations using a temperature series (80-400. K) of HED meteorite spectra that will enable interpretation of telescopic and spacecraft spectral data using laboratory calibrations at room temperature (300. K). © 2011 Elsevier Inc.
Fenton L.,Search for Extraterrestrial Intelligence Institute |
Reiss D.,Institute For Planetologie |
Lemmon M.,Texas A&M University |
Marticorena B.,Laboratoire Interuniversitaire des Systemes Atmospheriques |
And 2 more authors.
Space Science Reviews | Year: 2016
Over the past several decades, orbital observations of lofted dust have revealed the importance of mineral aerosols as a climate forcing mechanism on both Earth and Mars. Increasingly detailed and diverse data sets have provided an ever-improving understanding of dust sources, transport pathways, and sinks on both planets, but the role of dust in modulating atmospheric processes is complex and not always well understood. We present a review of orbital observations of entrained dust on Earth and Mars, particularly that produced by the dust-laden structures produced by daytime convective turbulence called “dust devils”. On Earth, dust devils are thought to contribute only a small fraction of the atmospheric dust budget; accordingly, there are not yet any published accounts of their occurrence from orbit. In contrast, dust devils on Mars are thought to account for several tens of percent of the planet’s atmospheric dust budget; the literature regarding martian dust devils is quite rich. Because terrestrial dust devils may temporarily contribute significantly to local dust loading and lowered air quality, we suggest that martian dust devil studies may inform future studies of convectively-lofted dust on Earth. As on Earth, martian dust devils form most commonly when the insolation reaches its daily and seasonal peak and where a source of loose dust is plentiful. However this pattern is modulated by variations in weather, albedo, or topography, which produce turbulence that can either enhance or suppress dust devil formation. For reasons not well understood, when measured from orbit, martian dust devil characteristics (dimensions, and translational and rotational speeds) are often much larger than those measured from the ground on both Earth and Mars. Studies connecting orbital observations to those from the surface are needed to bridge this gap in understanding. Martian dust devils have been used to remotely probe conditions in the PBL (e.g., CBL depth, wind velocity); the same could be done in remote locations on Earth. Finally, martian dust devils appear to play a major role in the dust cycle, waxing and waning in relative importance and spatial patterns of occurrence with the planet’s orbital state. Orbital studies of terrestrial dust devils would provide a basis for comparative planetology that would broaden the understanding of these dusty vortices on both planets. © 2016 Springer Science+Business Media Dordrecht
Goodrich C.,Planetary Science Institute |
Bischoff A.,Institute For Planetologie |
O'Brien D.P.,Planetary Science Institute
Elements | Year: 2014
On October 6, 2008, the small (∼4 m) asteroid 2008 TC3 was discovered and predicted to hit Earth within ∼19 hours. Photometric data and a reflectance spectrum were obtained. The asteroid fragmented at ∼37 km altitude above Sudan. Approximately 700 centimeter-sized fragments were recovered and constitute the meteorite Almahata Sitta. It is a unique meteorite breccia, consisting of ∼50-70% ureilitic materials, plus samples of nearly every major chondrite group. The reflectance spectrum of 2008 TC3 is closest to that of F-class asteroids, not previously associated with any meteorite type. 2008 TC3/Almahata Sitta records a complex history of fragmentation, migration, and reaccretion of materials in the Solar System.
Morlok A.,Institute For Planetologie |
Stojic A.,Institute For Planetologie |
Weber I.,Institute For Planetologie |
Hiesinger H.,Institute For Planetologie |
And 2 more authors.
Icarus | Year: 2016
We have analyzed 14 impact melt glass samples, covering the compositional range from highly felsic to mafic/basaltic, as part of our effort to provide mid-infrared spectra (7–14 µm) for MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer), an instrument onboard of the ESA/JAXA BepiColombo mission. Since Mercury was exposed to many impacts in its history, and impact glasses are also common on other bodies, powders of tektites (Irghizite, Libyan Desert Glass, Moldavite, Muong Nong, Thailandite) and impact glasses (from the Dellen, El'gygytgyn, Lonar, Mien, Mistastin, and Popigai impact structures) were analyzed in four size fractions of (0–25, 25–63, 93–125 and 125–250 µm) from 2.5 to 19 µm in bi-directional reflectance. The characteristic Christiansen Feature (CF) is identified between 7.3 µm (Libyan Desert Glass) and 8.2 µm (Dellen). Most samples show mid-infrared spectra typical of highly amorphous material, dominated by a strong Reststrahlen Band (RB) between 8.9 µm (Libyan Desert Glass) and 10.3 µm (Dellen). Even substantial amounts of mineral fragments hardly affect this general band shape. Comparisons of the SiO2 content representing the felsic/mafic composition of the samples with the CF shows felsic/intermediate glass and tektites forming a big group, and comparatively mafic samples a second one. An additional sign of a highly amorphous state is the lack of features at wavelengths longer than ∼15 µm. The tektites and two impact glasses, Irghizite and El'gygytgyn respectively, have much weaker water features than most of the other impact glasses. For the application in remote sensing, spectral features have to be correlated with compositional characteristics of the materials. The dominating RB in the 7–14 µm range correlates well with the SiO2 content, the Christiansen Feature shows similar dependencies. To distinguish between glass and crystalline phases of the same chemical composition, a comparison between CF the SCFM index (SiO2/(SiO2 + CaO + FeO + MgO)) (Walter and Salisbury  J. Geophys. Res., 94, 9203–9213) is useful, if chemical compositional data are also available. © 2016 Elsevier Inc.
Bischoff A.,Institute For Planetologie |
Dyl K.A.,Curtin University Australia |
Dyl K.A.,University of California at Los Angeles |
Horstmann M.,Institute For Planetologie |
And 4 more authors.
Meteoritics and Planetary Science | Year: 2013
The Villalbeto de la Peña meteorite that fell in 2004 in Spain was originally classified as a moderately shocked L6 ordinary chondrite. The recognition of fragments within the Villalbeto de la Peña meteorite clearly bears consequences for the previous classification of the rock. The oxygen isotope data clearly show that an exotic eye-catching, black, and plagioclase-(maskelynite)-rich clast is not of L chondrite heritage. Villalbeto de la Peña is, consequently, reclassified as a polymict chondritic breccia. The oxygen isotope data of the clast are more closely related to data for the winonaite Tierra Blanca and the anomalous silicate-bearing iron meteorite LEW 86211 than to the ordinary chondrite groups. The REE-pattern of the bulk inclusion indicates genetic similarities to those of differentiated rocks and their minerals (e.g., lunar anorthosites, eucritic, and winonaitic plagioclases) and points to an igneous origin. The An-content of the plagioclase within the inclusion is increasing from the fragment/host meteorite boundary (approximately An10) toward the interior of the clast (approximately An52). This is accompanied by a successive compositionally controlled transformation of plagioclase into maskelynite by shock. As found for plagioclase, compositions of individual spinels enclosed in plagioclase (maskelynite) also vary from the border toward the interior of the inclusion. In addition, huge variations in oxygen isotope composition were found correlating with distance into the object. The chemical and isotopical profiles observed in the fragment indicate postaccretionary metamorphism under the presence of a volatile phase. © The Meteoritical Society, 2013.