Research Interests

My interests are the exploration of Solar System objects and the understanding of their evolution. I am focusing on remote sensing of the solid surfaces of planets and their record of past environments. This research is enabled by space missions throughout the Solar System. Here below more details on my research methods.

 

 
 Visible to near infrared reflectance spectrum of a HED meteorite (analog to Vesta surface) measured in the laboratory. BI and BII indicate different absorption bands

Visible to near infrared reflectance spectrum of a HED meteorite (analog to Vesta surface) measured in the laboratory. BI and BII indicate different absorption bands

Planetary Visible and Near-Infrared Spectroscopy

This method characterizes the mineralogy of a planetary surface or a sample in the lab by analyzing the light it reflects. Absorption bands of rock-forming minerals, like pyroxene, olivine, phyllosilicates and carbonates can be detected, quantified and mapped across the surface of a planetary object. This tell us about how rocks formed, for example by magmatic processes, volcanism or aqueous alteration.

 
 Geologic map of a quadrangle on asteroid Vesta (~500 km in diameter). Colors indicate different geologic units, formed at different times and by different geologic processes.

Geologic map of a quadrangle on asteroid Vesta (~500 km in diameter). Colors indicate different geologic units, formed at different times and by different geologic processes.

Planetary Geology

This field exploits optical imagery and 3-D topographic model. Geomorphology, morphometry and stratigraphic relationship give information on the type and time of processes that affected the surface, like impact cratering, tectonic, or fluvial. Time information can also be gained with the so-called crater counting technique, or crater size-frequency distribution measurements, coupled with model and chronologies of impact history.

 

Explore New Planetary Surfaces

Multi-temporal database for the surface of Mars, developed by the Institute fur Planetologie,  University of Muenster.

PS. Some places on Mars are better (and more often) imaged than some places on Earth.

3D and 2D view of 11 different image datasets of the asteroid Vesta. Developed at JPL/NASA from the Dawn mission data.

PS. Once on the website, click the "3D" symbol on the bottom left for enhanced visualization.

 

 

A multitude of high resolution image layers for the Moon. Credits by LROC/ASU/NASA.

PS. Combine the different layers and get to know the hidden water-rich areas at the lunar poles.


Here below a summary of my PhD thesis on the asteroid Vesta. The full dissertation is also available at the bottom of this page.

 
IfP uni muenster

Geological evolution of asteroid Vesta from Dawn orbital observations and meteorite analogs

 

PhD dissertation defended at the Institut für Planetologie of the Westfälische Wilhelms-Universität Münster, Germany, May 2015. You can read the following abstract or click here for the complete publication.

The asteroid (4) Vesta is a ~500 km large main belt silicate body that accreted and
differentiated a few million years after condensation of the solar nebula. Terrestrial planets
have formed by accretion of similar planetary embryos. Thus, Vesta is interpreted as a
survivor protoplanet and the knowledge it yields is essential to understand the early stages of
planet formation.

To support mineralogical investigations of Vesta´s surface with near-infrared remote
sensing observations, I performed mineralogical and near-infrared (0.7-2.5 µm) analyses of 24
howardite-eucrite-diogenite (HED) meteorites analog to Vesta´s surface. With these analyses,
I established an empirical calibration relating the wavelength position of absorption bands to
average pyroxene compositions. Compared to previous studies, this calibration is based on a
larger meteorites sample and on consistent analyses. I characterized the influence of
observation geometry on several spectral features of HED near-infrared spectra (i.e.,
wavelength position and depth of absorption bands, spectral slopes, band area ratio). I
determined the range of phase angles within which the compositional variations (i.e.,
admixture of olivine or low-albedo material to pyroxene mixture) can be distinguished from
observation geometry effects.

I retrieved near-infrared reflectance spectra from the first orbital observations of Vesta
acquired by the visible to near-infrared imaging spectrometer (VIR) onboard the Dawn
spacecraft. Quantitative analyses of the VIR reflectance spectra using a radiative transfer
model revealed the presence of low-Ca and low-Fe pyroxene, high-Ca pyroxene, feldspar and
olivine. The ubiquitous presence of such components confirmed a compositionally
homogeneous upper layer (i.e., regolith). I applied the empirical calibration to VIR reflectance
spectra and found that Vesta´s iron-poor terrains have a Fs30Wo5 pyroxene composition,
whereas iron-rich terrains have an average Fs47Wo14 pyroxene composition. This confirms
that, despite a compositionally homogeneous regolith, different terrains are preserved on
Vesta, possibly formed during an early magmatic period. The composition and geologic
context of these terrains are broadly consistent with differentiation models for the HED parent
body. In addition, I exploited the unprecedented spatial resolution of the VIR reflectance
spectra to determine the global spatial distribution of olivine-enriched material on Vesta. A
concentration of olivine-enriched areas was found in the northern hemisphere.

I exploited the Dawn Framing Camera (FC) observations to compile a photo-geological
map of the northern hemisphere (22°N-90°N) and determine the stratigraphy using dating by
crater size-frequency distribution. The northern hemisphere is composed of an ancient (pre-
Veneneian epoch), densely cratered terrain, partly disrupted by a subdued tectonic system of
troughs and ridges, possibly formed by a large impact (Veneneian epoch). The presence of
olivine-enriched material in such a geologic context partly contradicts many pre-Dawn
concepts of Vesta´s interior structure and differentiation based on the HED parent body.

 Chronological table summarizing the geological history of Vesta, subdivided into Vesta´s four geological epochs. In the “Main processes” column, interpretations explaining the main observations and the different scenarios (a, b and c) for the Pre-Veneneian epoch are reported. Absolute model ages are based on the lunar chronology and impact history and are discussed in detail in the thesis.

Chronological table summarizing the geological history of Vesta, subdivided into Vesta´s four geological epochs. In the “Main processes” column, interpretations explaining the main observations and the different scenarios (a, b and c) for the Pre-Veneneian epoch are reported. Absolute model ages are based on the lunar chronology and impact history and are discussed in detail in the thesis.

As a consequence, new scenarios for the early evolution of Vesta (pre-Veneneian
epoch) have been proposed by other studies. However, none provide consistent explanation
for the entire range of observations reported here. In addition, the thesis revealed the
geological evolution of the olivine-enriched lithologies of Vesta after the pre-Veneneian
epoch. Most lithologies are probably the result of magmatic activity on Vesta and were
redistributed across the surface as impact ejecta. Olivine-rich materials were exposed in recent
time (Marcian epoch) by subsequent impacts and mass wasting.