Mid-infrared reflectance spectroscopy of calcium-aluminium-rich inclusions to identify primitive near Earth asteroids

The recent availability of mid-IR spectroscopy from space telescopes has led to studies attempting to characterise the composition of near Earth asteroids (NEAs) by comparison to spectroscopic observations of meteorites in the laboratory (e.g. [1, 2]). Mid-IR of carbonaceous chondrite meteorites has also recently been in focus to identify primitive asteroids and the aqueous alteration processes occurring on them [3]. Of special interest among the components of carbonaceous chondrites are the refractory calcium-aluminium-rich inclusions (CAIs) because they are formed very early on in the solar system. We have gathered reflectance spectra in the 2.5-16.0 μm range of the phases (spinel, olivine, melilite, pyroxene, etc.) in CAI sections of meteorites Allende (CV3.3), Vigarano (CV3.3) and Ornans (CO3.3) with a Perkin Elmer AutoIMAGE FTIR microscope, and compared them to mid-IR spectra of several NEA targets (253 Mathilde, 243 Ida, 1917 Cuyo, and the target of OSIRIS-Rex mission 101955 Bennu) of the Spitzer Space Telescope's Infrared Spectrometer (IRS [4]). Spectra from Spitzer were extracted with an optimal extraction method [5] and corrected with a near earth thermal model [6]. Reflectance spectra obtained from the CAIs were compared to spectra in the Keck/NASA RELAB database [7]. Overall, we see some features on the surfaces of the observed asteroids that may correspond to the pristine CAIs from the chondrites, though identification of these features is not easy. References: [1] Emery, J. P. et al. (2006) Icarus, 182, 496-512. [2] Lim, L. F. et al. (2011) Icarus, 213, 510-523. [3] Trigo-Rodriguez, J. M. et al. (2014) Mon. Not. R. Astron. Soc. 437, 227-240. [4] Houck, J. R. et al. (2004) Astron. Phy. J. Suppl. 154, 18-24. [5] Lebouteiller, V. et al. (2010) Publ. Astron. Soc. Pac., 122.888, 231-240. [6] Harris, A. W. (1998) Icarus 131, 291-301. [7] Pieters, C. M., and Hiroi, T. (2004). Lunar Planet. Sci. XXXV, # 1720

A shock recovery experiment and its implications for Mercury's surface : The effect of high pressure on porous olivine powder as a regolith analog

We conducted classic dynamic high - pressure experiments on porous San Carlos (SC) olivine powder to examine if and how different shock stages modify corresponding reflectance mid – infrared (MIR) spectra. Microscopic investigation of the thin sections produced of our shocked samples indicates local peak pressures of >60 GPa along with all lower grade shock stages. Spectral analyses of optically identified shock areas were documented and compared in terms of Christiansen Feature (CF) and the position of olivine – diagnostic Reststrahlenbands (RBs). We found that one RB (fundamental vibrations of the orthosilicate - ion) of olivine occurring at 980 cm−1 (corresponding to ≈ 10.2 μm) shows the least energetic shift in the investigated MIR spectra and could therefore serve as a proxy for the presence of olivine in remote sensing application. Furthermore, a peak located at ≈ 1060 cm−1 (≈ 9.4 μm) shows a significant intensity change probably related to the degree of shock exposure or grain orientation effects, as we observe a decline in intensity of this band from our averaged reference olivine spectra of our IRIS database (diffuse reflectance measurement) down to spectra of grains showing mosaicism and recrystallized areas. We also report the presence of a weak band in some of the olivine spectra located at ≈ 1100 cm−1 (9.1 μm) that has an influence on the position of the CF when spectral data of olivine are averaged.Peer reviewe

Planet Formation Imager (PFI): Science vision and key requirements

The Planet Formation Imager (PFI) project aims to provide a strong scientific vision for ground-based optical astronomy beyond the upcoming generation of Extremely Large Telescopes. We make the case that a breakthrough in angular resolution imaging capabilities is required in order to unravel the processes involved in planet formation. PFI will be optimised to provide a complete census of the protoplanet population at all stellocentric radii and over the age range from 0.1 to ∼100 Myr. Within this age period, planetary systems undergo dramatic changes and the final architecture of planetary systems is determined. Our goal is to study the planetary birth on the natural spatial scale where the material is assembled, which is the Hill Sphere of the forming planet, and to characterise the protoplanetary cores by measuring their masses and physical properties. Our science working group has investigated the observational characteristics of these young protoplanets as well as the migration mechanisms that might alter the system architecture. We simulated the imprints that the planets leave in the disk and study how PFI could revolutionise areas ranging from exoplanet to extragalactic science. In this contribution we outline the key science drivers of PFI and discuss the requirements that will guide the technology choices, the site selection, and potential science/technology tradeoffs

The Stubenberg meteorite—An LL6 chondrite fragmental breccia recovered soon after precise prediction of the strewn field

On March 6, 2016 at 21:36:51 UT, extended areas of Upper Austria, Bavaria (Germany) and the southwestern part of the Czech Republic were illuminated by a very bright bolide. This bolide was recorded by instruments in the Czech part of the European Fireball Network and it enabled complex and precise description of this event including prediction of the impact area. So far six meteorites totaling 1473 g have been found in the predicted area. The first pieces were recovered on March 12, 2016 on a field close to the village of Stubenberg (Bavaria). Stubenberg is a weakly shocked (S3) fragmental breccia consisting of abundant highly recrystallized rock fragments embedded in a clastic matrix. The texture, the large grain size of plagioclase, and the homogeneous compositions of olivine (Fa31.4) and pyroxene (Fs25.4) clearly indicate that Stubenberg is an LL6 chondrite breccia. This is consistent with the data on O, Ti, and Cr isotopes. Stubenberg does not contain solar wind-implanted noble gases. Data on the bulk chemistry, IR spectroscopy, cosmogenic nuclides, and organic components also indicate similarities to other metamorphosed LL chondrites. Noble gas studies reveal that the meteorite has a cosmic ray exposure (CRE) age of 36 ± 3 Ma and that most of the cosmogenic gases were produced in a meteoroid with a radius of at least 35 cm. This is larger than the size of the meteoroid which entered the Earth's atmosphere, which is constrained to <20 cm from short-lived radionuclide data. In combination, this might suggest a complex exposure history for Stubenberg.PostprintPeer reviewe

Rationale for BepiColombo Studies of Mercury's Surface and Composition

BepiColombo has a larger and in many ways more capable suite of instruments relevant for determination of the topographic, physical, chemical and mineralogical properties of Mercury's surface than the suite carried by NASA's MESSENGER spacecraft. Moreover, BepiColombo's data rate is substantially higher. This equips it to confirm, elaborate upon, and go beyond many of MESSENGER's remarkable achievements. Furthermore, the geometry of BepiColombo's orbital science campaign, beginning in 2026, will enable it to make uniformly resolved observations of both northern and southern hemispheres. This will offer more detailed and complete imaging and topographic mapping, element mapping with better sensitivity and improved spatial resolution, and totally new mineralogical mapping. We discuss MESSENGER data in the context of preparing for BepiColombo, and describe the contributions that we expect BepiColombo to make towards increased knowledge and understanding of Mercury's surface and its composition. Much current work, including analysis of analogue materials, is directed towards better preparing ourselves to understand what BepiColombo might reveal. Some of MESSENGER's more remarkable observations were obtained under unique or extreme conditions. BepiColombo should be able to confirm the validity of these observations and reveal the extent to which they are representative of the planet as a whole. It will also make new observations to clarify geological processes governing and reflecting crustal origin and evolution. We anticipate that the insights gained into Mercury's geological history and its current space weathering environment will enable us to better understand the relationships of surface chemistry, morphologies and structures with the composition of crustal types, including the nature and mobility of volatile species. This will enable estimation of the composition of the mantle from which the crust was derived, and lead to tighter constraints on models for Mercury's origin including the nature and original heliocentric distance of the material from which it formed.Peer reviewe

Planet Formation Imager (PFI): science vision and key requirements

The Planet Formation Imager (PFI) project aims to provide a strong scientific vision for ground-based optical astronomy beyond the upcoming generation of Extremely Large Telescopes. We make the case that a breakthrough in angular resolution imaging capabilities is required in order to unravel the processes involved in planet formation. PFI will be optimised to provide a complete census of the protoplanet population at all stellocentric radii and over the age range from 0.1 to ~100 Myr. Within this age period, planetary systems undergo dramatic changes and the final architecture of planetary systems is determined. Our goal is to study the planetary birth on the natural spatial scale where the material is assembled, which is the "Hill Sphere" of the forming planet, and to characterise the protoplanetary cores by measuring their masses and physical properties. Our science working group has investigated the observational characteristics of these young protoplanets as well as the migration mechanisms that might alter the system architecture. We simulated the imprints that the planets leave in the disk and study how PFI could revolutionise areas ranging from exoplanet to extragalactic science. In this contribution we outline the key science drivers of PFI and discuss the requirements that will guide the technology choices, the site selection, and potential science/technology tradeoffs.S.K. acknowledges support from an STFC Rutherford Fellowship (ST/J004030/1) and Philip Leverhulme Prize (PLP-2013-110). Part of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration

Mid-infrared reflectance spectroscopy of calcium-aluminium-rich inclusions to identify primitive near Earth asteroids

The recent availability of mid-IR spectroscopy from space telescopes has led to studies attempting to characterise the composition of near Earth asteroids (NEAs) by comparison to spectroscopic observations of meteorites in the laboratory (e.g. [1, 2]). Mid-IR of carbonaceous chondrite meteorites has also recently been in focus to identify primitive asteroids and the aqueous alteration processes occurring on them [3]. Of special interest among the components of carbonaceous chondrites are the refractory calcium-aluminium-rich inclusions (CAIs) because they are formed very early on in the solar system. We have gathered reflectance spectra in the 2.5-16.0 μm range of the phases (spinel, olivine, melilite, pyroxene, etc.) in CAI sections of meteorites Allende (CV3.3), Vigarano (CV3.3) and Ornans (CO3.3) with a Perkin Elmer AutoIMAGE FTIR microscope, and compared them to mid-IR spectra of several NEA targets (253 Mathilde, 243 Ida, 1917 Cuyo, and the target of OSIRIS-Rex mission 101955 Bennu) of the Spitzer Space Telescope's Infrared Spectrometer (IRS [4]). Spectra from Spitzer were extracted with an optimal extraction method [5] and corrected with a near earth thermal model [6]. Reflectance spectra obtained from the CAIs were compared to spectra in the Keck/NASA RELAB database [7]. Overall, we see some features on the surfaces of the observed asteroids that may correspond to the pristine CAIs from the chondrites, though identification of these features is not easy. References: [1] Emery, J. P. et al. (2006) Icarus, 182, 496-512. [2] Lim, L. F. et al. (2011) Icarus, 213, 510-523. [3] Trigo-Rodriguez, J. M. et al. (2014) Mon. Not. R. Astron. Soc. 437, 227-240. [4] Houck, J. R. et al. (2004) Astron. Phy. J. Suppl. 154, 18-24. [5] Lebouteiller, V. et al. (2010) Publ. Astron. Soc. Pac., 122.888, 231-240. [6] Harris, A. W. (1998) Icarus 131, 291-301. [7] Pieters, C. M., and Hiroi, T. (2004). Lunar Planet. Sci. XXXV, # 1720

Mikrosondenanalytik und Sekundärionenmassenspektrometrie an Fragmenten und Lithologien in CI-Chondriten

Silikatreiche Fragmente in den primitiven CI-Chondriten wurden mit Elektronenstrahl- Mikrosonde, TOF-SIMS und DF-SIMS auf ihre chemische Zusammensetzung hin untersucht. Die Gehalte von einigen Elementen (z.B. Fe, Na, S, P, Ca, K, Mn, Ti, SEE) weisen große Schwankungen unter den Fragmenten auf. Grund für diese Heterogenität sind ungleich verteilte Phasen wie z.B. Magnetite, Eisenhydroxide, Sulfate oder Phosphate. Mit Hilfe u.a. von multivarianten statistischen Verfahren (Clusteranalyse) erfolgte eine Einteilung der Fragmente in Lithologien. Diese entsprechen gemäß Modellierungen möglicherweise Phasen während der aquatischen Alteration des Mutterkörpers der CI-Chondrite. Ein Vergleich der Bandbreiten der Zusammensetzung von Fragmenten und verschiedener Gesamtanalysen ergab Hinweise auf Heterogenität auch größerer Bereiche in CI-Chondriten, möglicherweise aufgrund der ungleichen Verteilung der Lithologien