Volcanism, crustal cooling and impact history of the differentiated asteroid Vesta through the lens of the 40Ar/39Ar technique
Abstract
Based on 40Ar/39Ar analyses of different components (mineral,
matrix, melt) of HED meteorites, the history of volcanism, crustal cooling
and impact history will be elucidated.
The Impact of Impact
Abstract
This presentation covers the identification of evidence to support a large
meteorite impact at the Cretaceous-Paleocene boundary (K-Pg) 66 million
years and the discovery and recent drilling of the Chicxulub crater in
Yucatan. It also discusses how this major planetary collision triggered a
rapid and brutal global environmental change that led to the demise of the
non-avian dinosaurs and fauna and flora on Earth.
Infrared Spectroscopy for the BepiColombo Mission to Mercury
Abstract
Mercury, the innermost planet of the Solar System, is characterized by a
heavily cratered surface, a lare core and a strong magnetic field. It was
rarely visited by space probes, the ESA/JAXA mission to Mercury arriving
in 2025 is only the third visit so far. Onboard is a suite of instruments
allowing to investigate Mercury in high detail. This talk will focus on
the MERTIS instrument. MERTIS (Mercury Radiometer and Thermal Infrared
Spectrometer) will allow to map most of the hermean surface in the
mid-infrared, a spectral region so far not covered in earlier missions.
With the help of the expected data, the surface composition and mineralogy
of Mercury will be determined in detail for the first time. The
presentation will be about our work at the IRIS laboratory in Münster,
where we conduct laboratory measurements for the interpretation of the
expected result.
A Time-Line for the Formation of Terrestrial Planets
Abstract
Chemical and isotopic analyses of primitive meteorites reveal that the
building blocks of the rocky planets in our solar system are derived from
different nucleosynthetic sources. These diverse materials were mixed at
an early stage and provided the matter that ended up in the solar system
bodies. The path from a gas-dust cloud to the final arrangement of the
planets in our solar system took several 10s of million years and involved
different processes, including condensation and evaporation, melting,
collision and differentiation of planetesimals, impacts and metamorphism.
A specific, and possibly unique, sequence of events and processes led to
the formation of the Earth, the only known planet that brought forth life
and sustained it for billions of years. Information on the early
evolution of the solar system is stored in meteorites and their components
and also can be reconstructed from the bulk composition of planets,
particularly the Earth. A key piece of information for a good
understanding of the dynamic evolution of our own planetary system is the
timing of different physical and chemical processes and events in the
early solar system. To this end geochronological information from
meteorites needs to be combined with their chemical and isotopic
composition.
Tin stable isotope variations in natural materials: Implications for planetary and nebular processes
Abstract
The mass dependent isotope variation in volatile elements could act as
useful proxies to understand the early solar system conditions, where
materials processed through evaporation and condensation in the solar
nebula was eventually incorporated by planetesimals during their
accretion. The isotope composition of H and O, in a water molecule are
subjected to modification during such physico-chemical processes, and
hence it is difficult to readily extract information from them with less
uncertainty. Tin being a moderately volatile element could be used to
trace the origin of
volatile components in a terrestrial planet like Earth. Due to a unique
geochemical behavior of being both chalcophile and siderophile, Sn also
additionally enables understanding the core formation process of Earth
using iron meteorites and high P-T experimental products, as proxies. A
novel wet chemistry based methodology was developed to provide these
answers by precisely measuring stable Sn isotope variations in terrestrial
and meteorite samples using a double spike MC-ICP-MS technique. Given the
significance of such volatile elements, I will present the challenges in
developing analytical methods for measuring Sn isotopes, and some results
obtained from analyses of few terrestrial and chondrite samples.
Primordial noble gas component hosted by water-susceptible materials in less-altered CR chondrites
Abstract
Previous studies of noble gases in primitive meteorites have focused
primarily on acid-resistant phases that contain most of the noble gases
in the primitive meteorites. However, a new Ne-rich noble gas component
hosted by water-susceptible materials was recently found in some
aqueously less-altered CR chondrites. In this seminar, I will talk about
the potential relationship between the Ne-rich materials in CR
chondrites and cometary materials. The talk also briefly introduces
basic knowledge of noble gases in primitive meteorites and why noble
gases are unique tracers in cosmochemistry.
How hot and wet is the Moon: Insight from experiments
Abstract
The thermal profile of the Moon (selenotherm) is required to determine its
present-day interior structure and composition, and yet it is not
constrained well. How can we constrain the selenotherm better? Also,
measurements on lunar samples indicate that the Moon is not ‘bone dry’ but
does have some hydrogen in its interior. The bulk lunar hydrogen is an
important constraint to understand the dynamics of the Moon-forming impact
as well as determine the origin of volatiles in the Earth-Moon system. The
estimates of bulk lunar hydrogen span across a few orders of magnitude,
but how can we constrain it better? In this talk, I will discuss how we
can better estimate both the thermal state and the bulk lunar hydrogen to
improve our understanding of lunar evolution.
The Terrestrial Impact Record
Abstract
The recognition of impact craters on the Earth is difficult, because
active geological and atmospheric processes on our planet obscure or erase
the impact record in geologically short time periods. For the confirmation
of impact craters on Earth, detailed mineralogical, petrographic, and
geochemical studies are needed. Nevertheless, about 200 terrestrial impact
craters have been identified. On Earth, the first impact evidence exists
in the form of various spherule layers in South Africa and Australia, aged
between about 3.4 and 2.5 Ga. The oldest preserved impact structures have
ages of 2.02 and 1.86 Ga. Thus, there is little information about the
impact record and its effects during the first 2.5 billion years of Earth
history, but it is clear that then and later, impacts had severe effects
on the geological and biological evolution on Earth.
Mars - A short history through time
Abstract
The presentation will introduce the main geological processes acting on
Mars, which are typical and common on Earth-like planets. Furthermore, it
will provide insight into the geological evolution of Mars based on
remote-sensing data. Using meteorites from Mars, one can extract detailed
information on the rocks and minerals, as well as temporal constraints.
Globally, sequencing of events relies on crater statistics. While Mars now
appears to be rather a cold desert, in the past water has been more
abundant. This is evident in martian morphology and mineralogy.
Exploration of Mars with the help of spectral analyses indicate surface
weathering and mineral formation that requires water. The different
atmosphere composition, however, challenges simple transfer of process
details from Earth to Mars. Nevertheless, Earth rocks and terrestrial
analogue studies and experiments improve understanding Mars' evolutionary
history.
Aqueous alteration of primitive meteorites
Abstract
Evidence for aqueous alteration can be found in essentially all chondrite
groups and is pronounced in CI, CM, and CR chondrites. The aqueous
alteration played an important roll in material evolution on water-rich
planetesimals and thus an understanding of water activity is crucial to
investigate how volatile materials including ice and organic matter were
modified from their original forms in planetesimals before their delivery
to terrestrial planets. In this seminar, I am talking about pristine
materials in chondrites and how they were transformed by aqueous
alteration in their parent bodies. I am focusing on the timing and the
conditions such as temperature and water to rock ratios of the aqueous
alteration. I will also raise a few unsolved questions about aqueous
alteration for future research directions.
Thermal alteration of CM chondrites: Mineralogical changes and metamorphic temperature
Abstract
Most CM chondrites experienced only low temperature (<300C) aqueous
alteration in the early solar system. However, a number also record an
episode of post-hydration thermal metamorphism at temperatures up to
1000C. Remote observations suggest that such materials may be common on
the surface of primitive asteroids. We are therefore investigating the
mechanism, timing, and duration of metamorphism in CM chondrites to better
understand the thermal history of volatile-rich asteroids and provide
context for samples returned from Ryugu and Bennu by the Hayabusa2 and
OSIRIS-REx missions.
Understanding Planetary Differentiation from Hf-W systematics
Abstract
The source of one of the largest group of differentiated planets (asteroid
4 Vesta) is a differentiated planet with a metallic core. Meteorites from
this asteroid collectively referred to by acronym HEDs (howardite,
eucrite, and diogenites) provide a valuable avenue for studying evolution
of rocky terrestrial planets. These small rocky bodies arrested in
different stages of evolution, preserve information about processes that
have been erased on larger planets due to their prolonged activity.
Differentiated silicate rich meteorites are depleted siderophile elements
while Fe meteorites are rich rich in these elements. The homogeneous
oxygen isotope composition
support large scale melting event on the planetary body resulting in a
metallic core and a silicate mantle, very much like Earth, Moon and Mars.
I will explore the elemental distribution of W in these silicate rich
meteorites and 182Hf-182W isotope systematics to constrain the process of
planetary differentiation.
The Ancient Climate of Mars: Was the Ambient Climate 'Warm and Wet' or 'Cold and Icy'?
Abstract
One of the most fundamental questions in planetary science today is the
nature of the ambient climate of early Mars (Noachian-Early Hesperian):
Was the ambient climate “warm and wet”, as suggested by widespread
phyllosilicates, higher erosion rates, enhanced crater degradation, valley
networks, and open/closed-basin lakes? Or was the ambient climate “cold
and icy”, as suggested by recent climate models, with occasional
perturbations causing heating and melting of surface snow and ice, and
runoff to produce the observed characteristics and features? Using the
framework of these two ambient climate options, we will discuss
outstanding questions and how these might be resolved. We will also
explore the roles of the NASA Mars 2020 mission to the Jezero Crater
open-basin lake, and the CNSA Tianwen-1 mission to Utopia Planitia in
addressing these issues.
Meteorites from Morocco: An overview
Abstract
An overview of meteorites from Morocco will be given in this talk.
Meteorites are extraterrestrial rocks. They are crucial not only to the
apparition of water and life on Earth but also to the mass extinction of
species. Meteorites are mostly found in cold deserts such as Antarctica
and hot ones such as Oman, Sahara and Chili. The Sahara, and especially
the Moroccan one, provides a significant number of meteorites for
researchers and collectors all over the world.
Hands-on Astrophysics: Analysis of Presolar Stardust Grains to Decipher Stellar Nucleosynthesis
Abstract
The talk introduces how analyses of presolar stardust grains allow us to
decipher the slow neutron-capture (s-) process in asymptotic giant branch
stars. These measurements are therefore valuable to better understand how
the material the Solar System formed from came together in the first
place. The talk also introduces resonance ionization mass spectrometry
(RIMS), a technique that allows us to analyze the trace element isotopic
composition in such micrometer-sized samples. Finally, the background of
stellar nucleosynthesis and existing measurements to constrain the
s-process are discussed before concluding with an outlook to future RIMS
measurements.
Condensation and Radial Transport of Filamentary Enstatite Crystals from Interplanetary Dust
Abstract
Filamentary enstatite crystals, formed by gas-solid condensation in the
solar nebula, are found in chondritic porous interplanetary dust particles
of probable cometary origin. We measured the oxygen isotopic composition
of five filamentary enstatite grains from the giant cluster interplanetary
dust particle U2-20 GCP. These grains sample both the 16O-rich solar
(∆17O ≈ −30 per mil) and 16O-poor planetary (∆17O
≈ 0 per mil) isotope reservoirs. Our measurements provide evidence
for very early vaporization of dust-poor and dust-rich regions of the
solar nebula, followed by condensation and outward transport of
crystalline dust to the comet-forming region very far from the Sun.
Similar processes are likely responsible for the crystalline silicates
observed in the outer regions of protoplanetary disks elsewhere in the
Galaxy.
Atomic-Scale Structure and Non-Stoichiometry of Meteoritic Hibonite
Abstract
Hibonite (CaAl12O19) is a common refractory mineral in Ca-Al-rich
inclusions (CAIs) in primitive meteorites and provides crucial insights
into the conditions and processes that existed in the early solar nebula.
Transmission electron microscope (TEM) studies have identified enigmatic
planar defects in different occurrences of hibonite in the Allende
meteorite. Atomic resolution high-angle annular dark-field (HAADF) imaging
and energy dispersive X-ray (EDX) analyses were used to determine the
nature and origin of these planar features. Our TEM analyses revealed that
the modification of the stacking sequence in hibonite and its
non-stoichiometry (i.e., Al and Mg excesses) likely played a major role in
the formation and metastability of planar defects in hibonite. The
formation history of planar defects in hibonite will be discussed to
provide implications on the formation conditions for refractory first
solids in the early and high-temperature evolution stage of our Solar
System.
Volatiles on Mars - from meteorites to sample return
Abstract
Volatiles on Mars come in two categories: those, which react or are reaction
products, and those which are inert. The latter are the noble gases, which
can record processes such as degassing or atmospheric loss without taking
part in any reactions that might also happen. In the Martian meteorites
they present a complex story that to this day has conundrums to offer –
but maybe, just maybe we are getting an atmospheric sample with the first
ever sample return mission that would allow us to solve a few of the open
questions. Of the volatiles that react or are products of reaction,
methane captures our imagination most, because it is enigmatic in its
sporadic occurrence, and it could, maybe, if Earth is a good proxy, with
all the hedging that language has to offer, be linked to life. But of
course, we do not know that. What we know is that water has a long history
on Mars, carved channels, and most importantly for this part of the story,
altered minerals. This talk will present a personal journey of 25 years of
research into the sources, pathways, reactions and sinks of noble gases,
methane and water. Thus, the selection is biased, and very much guided by
the speaker’s own excitement about topics such as the Kr/Xe ratio in the
nakhlite Martian meteorites and the water rock reactions that form
carbonates on Mars.
Condensation and Radial Transport of Filamentary Enstatite Crystals from Interplanetary Dust
Abstract
Filamentary enstatite crystals, formed by gas-solid condensation in the
solar nebula, are found in chondritic porous interplanetary dust particles
of probable cometary origin. We measured the oxygen isotopic composition
of five filamentary enstatite grains from the giant cluster interplanetary
dust particle U2-20 GCP. These grains sample both the 16O-rich solar
(∆17O ≈ −30 per mil) and 16O-poor planetary (∆17O
≈ 0 per mil) isotope reservoirs. Our
measurements provide evidence for very early vaporization of dust-poor and
dust-rich regions of the solar nebula, followed by condensation and
outward transport of crystalline dust to the comet-forming region very far
from the Sun. Similar processes are likely responsible for the crystalline
silicates observed in the outer regions of protoplanetary disks elsewhere
in the Galaxy.
Chondrule formation: A controversial issue among different models
Abstract
Chondrites are the most primitive meteorites that preserve useful
information about the time the Solar System formed, about 4.56 Ga ago. One
of their major constituents are chondrules, μm to mm sized spherical
objects which constitute up to 80% of the volume of the most primitive
meteorites and are composed mainly of ferromagnesian silicates. The
process/es involved in chondrule formation cover a wide range of
mechanisms whose nature is still unknown. I will discuss the two principal
models that are outlined concerning the origin of chondrules in the solar
nebula. There is no real consensus regarding the nature of the initial
liquid droplets from which
chondrules are supposed to be formed, nor about the different processes
that were active during and after chondrule formation. An alternative
model: the Primary Liquid Condensation (PLC) model can explain the growth
of single crystals through a process in which liquid condenses first and
then nucleates a crystal of the species that is oversaturated in the
vapor. This process refers to a vapor-liquid-solid growth process that
take place in equilibrium with a chondritic reservoir. Finally, I will
inform of the
first glass inclusion hosted in spinel within a glass-rich chondrule from
the unequilibrated ordinary chondrite Catalina 278 (LL3.4). A possible
sample of the initial liquid trapped during spinel growth.
Origin and evolution of nitrogen on planetary bodies in the inner solar system
Abstract
Knowledge of the origin of nitrogen on Earth is of particular importance
to understanding the development of conditions favorable to the emergence
of prebiotic molecules and the maintenance of life on rocky planets.
However, the origin and timing of the accretion of nitrogen on Earth
remains a
subject of controversy. In this talk, I will present new data obtained by
secondary ion mass spectrometry (SIMS) analyses of extraterrestrial melt
inclusions. First, I will show that olivine-hosted melt inclusions in
angrites and martian meteorites are key for constraining the source(s) and
timing of nitrogen delivery to planetary bodies in the inner solar system.
However, the effects of planetary formation processes (core formation,
magma ocean crystallization and degassing) on the original elemental
and isotopic composition of planetary mantles still need to be investigated.
How well can we link meteorites to asteroids
Abstract
Asteroids are the remaining planetesimals that helped form the terrestrial
and Jovian planets. Asteroids, which are the parent bodies of almost all
meteorites, are almost entirely observed remotely using Earth- and
space-based telescopes with only a few bodies studied up close by
spacecraft missions. The chemical and isotopic compositions of meteorites
can be determined with high precision in laboratories on Earth; however,
remote observations of asteroids give geochemical information. In this seminar
asteroid-meteorite relationship will be discussed.
Nucleosynthetic heterogeneity in the early solar system: insights from Nd isotopes
Abstract
Isotopic variability from heterogeneous distribution of presolar dust
in the solar protoplanetary disk is now well-established for a number
of elements. Yet, significant uncertainty exists regarding the inventory
of presolar dust populations that were initially present in the protosolar
molecular cloud and their eventual aggregation into planets and
planetesimals. In this talk, I will review what high precision Nd isotope
measurements of meteorites and their components tell us about the
diversity of nucleosynthetic components that contributed material to the
nascent solar system and how they resulted in an apparent bifurcation of
solar system materials into carbonaceous and non-carbonaceous suites.