Vera Assis Fernandes | Universidade de Coimbra (original) (raw)

Papers by Vera Assis Fernandes

The Planetary Science Journal

Detailed spectral mapping, cratering statistics, and impact basin ejecta column estimates documen... more Detailed spectral mapping, cratering statistics, and impact basin ejecta column estimates document a new and very different stratigraphic relationship for the Apollo 14 landing site. We observe a resurfacing event in the crater size–frequency distribution in agreement with a single blanketing layer. Using the crater size–frequency distribution, we determine two relative ages (cumulative crater frequencies) that match those observed for the Imbrium and Orientale basins, respectively. The pattern and strength of resurfacing and morphological distinction by spectral features suggest the top layer to be about 10–25 m thick. We propose that this top layer at the Apollo 14 landing site is Orientale basin ejecta above Imbrium basin ejecta. Such stratigraphy reattributes the (majority of) Apollo 14 samples to Orientale rather than to Imbrium basin and implies that Orientale basin is about 3.92 Gyr old, 200 million years older than previously suggested. The youngest lunar basin thus formed a...

Table A1 Summary of literature age data for NA Tektites and the Chesapeake Bay impact structure o... more Table A1 Summary of literature age data for NA Tektites and the Chesapeake Bay impact structure obtained using different analytical techniques: biostratigraphy, fission-track, 40Ar/39Ar total fusion and step heating, K/Ar and U/Pb. Where possible, sample ages have been corrected using the Steiger and Jäger (1977) decay constants and consistent monitor ages (Schwarz and Trieloff, 2007). Table A2 Chemical composition for a profile along a bediasite obtained by electron microprobe (in wt%). Table A3 Chemical composition for a profile along a georgiaite obtained by electron microprobe (in wt%). Appendix tables A4-A20 display measured argon isotopes corrected for mass discrimination, sensitivity, system blanks, decay and relative neutron doses. All isotopes are also corrected for interfering isotopes produced on K and Ca during irradiation.

This data set contains bulk rock, mass-dependent (42Ca/44Ca and 43Ca/44Ca) and mass-independent (... more This data set contains bulk rock, mass-dependent (42Ca/44Ca and 43Ca/44Ca) and mass-independent (48Ca/44Ca) calcium isotope compositions of chondrites (carbonaceous and ordinary) as well as terrestrial rock standards, lunar, Martian, ureilite, eucrite and angrite meteorites reported relative to the SRM 915b standard. Samples were analysed to investigate Solar System and planet formation processes. All data were produced by wet chemical analysis on a multi-collector inductively coupled plasma mass spectrometer following separation of calcium from its matrix through ion exchange chromatography.

Nature, Jan 21, 2018

Nucleosynthetic isotope variability among Solar System objects is often used to probe the genetic... more Nucleosynthetic isotope variability among Solar System objects is often used to probe the genetic relationship between meteorite groups and the rocky planets (Mercury, Venus, Earth and Mars), which, in turn, may provide insights into the building blocks of the Earth-Moon system. Using this approach, it has been inferred that no primitive meteorite matches the terrestrial composition and the protoplanetary disk material from which Earth and the Moon accreted is therefore largely unconstrained. This conclusion, however, is based on the assumption that the observed nucleosynthetic variability of inner-Solar-System objects predominantly reflects spatial heterogeneity. Here we use the isotopic composition of the refractory element calcium to show that the nucleosynthetic variability in the inner Solar System primarily reflects a rapid change in the mass-independent calcium isotope composition of protoplanetary disk solids associated with early mass accretion to the proto-Sun. We measure ...

Earth and Planetary Science Letters, 2015

The composition of mare basalt units in the Orientale Basin are investigated by using the potassi... more The composition of mare basalt units in the Orientale Basin are investigated by using the potassium (K) map derived from Chang'E-2 gamma-ray spectrometer (CE-2 GRS) and FeO map derived from Clementine UV-Vis data set. Together with crater retention ages of the mare basalts from literature data, we aim to investigate possible magma sources underneath the Orientale Basin and their chemical evolution over time. Analyses of the chemical composition of the resurfaced mare basalts together with the reported eruption ages suggest a unique magma generating process for the resurfaced mare deposits. The early mare basalts in the central Mare Orientale and the later resurfaced mare deposits probably derived from magma generated by heat release due to high radioactive element concentrations. Based on forward modeling, the similar K abundances observed in the small mare deposits of the SW polygon area, Lacus Veris, and Lacus Autumni and those in the central Mare Orientale imply the same heat source for these lava eruptions. The chemical similarities (e.g., K, FeO, and TiO 2) of these regions suggest that mare basalts within the Orientale Basin are a result of multiple eruptions from a relatively homogeneous source underneath the Basin.

ABSTRACT abst.# EGU2013-10538-2

37th Annual Lunar and Planetary …, 2006

Ar-Ar experiments have been conducted on two lunar meteorites, LAP02205 and EET96008, to determin... more Ar-Ar experiments have been conducted on two lunar meteorites, LAP02205 and EET96008, to determine the age of the formation and later events on the history of these meteorites. Age for LAP is~ 2.92 Ga and for EET is 3.22 Ga. Final work is underway.

Geochimica et Cosmochimica Acta, 2000

ABSTRACT

Two Ar-Ar techniques are used to date clasts in highland lunar meteorites, Dho 025, 026, 280, 303... more Two Ar-Ar techniques are used to date clasts in highland lunar meteorites, Dho 025, 026, 280, 303: UV laser spot fusion and IR laser in-situ step-heating. Most of the clasts are characterized by high volume correlated ^40Ar not related to the low-K.

Meteoritics and Planetary …, 2000

... The Voyager upper limit for CO the Loki plume is CO 2.5-7.5 x 10 A comparison of this upper l... more ... The Voyager upper limit for CO the Loki plume is CO 2.5-7.5 x 10 A comparison of this upper limit with CO calculated as a function of the bulk ... VA Fernandes, R. Burgess, and G. Turner, Department of Earth Sciences, University of Manchester, UK (viemandes@fslge.man.ac.uk). ...

During this new 2010-decade, it will be imperative to reconsider the effectiveness of the current... more During this new 2010-decade, it will be imperative to reconsider the effectiveness of the current United Nations (UN) Moon Treaty (c. 1979). Amendments are necessary to underline the mandatory human stewardship of this fragile planetary body of our Solar System, indispensible to life on Earth. After the very successful Apollo and Luna missions to the Moon (ending in 1976), which brought a wide array of data (samples, surface and orbital experiments), the Moon lost its exploratory attraction in favor of other programs, such as ...

For several decades, scientists have been voicing concern over "planetary protection" (... more For several decades, scientists have been voicing concern over "planetary protection" (PP). To an outside observer unaware of this term's nuances, the phrase could easily be taken to include problems related to environmentalism, such as preservation of the natural landscape and natural resources. Instead, the term, as it is used today, refers only to practices intended to minimize biological contamination – of the Earth by extraterrestrial life, and vice-versa. The emergence, on the one hand, of private industries interested in exploiting space-based resources (e.g., mining the Moon for 3He) and the growth, on the other hand, of broad public support for environmental protections here on Earth, together suggest that the time is ripe to re-consider the full range of possible impacts caused by human activity in space be-fore irreparable harm is caused to the cosmic environment. This paper aims to unpack the concept of planetary protection, identifying its primary limitati...

Introduction: The Laser Ablation Time-Of-Flight Mass Spectrometry (LA-TOF MS) is a well accepted ... more Introduction: The Laser Ablation Time-Of-Flight Mass Spectrometry (LA-TOF MS) is a well accepted method for the acquisition of chemical composition of solid materials. Miniaturized LA-TOF MS’s have recently been developed for space research and are considered to be an important part of the instrumentation dedicated to study planetary surfaces[1-4]. They offer rapid analysis of the entire elemental and isotopic composition of well spatially resolved (10-50 m) sections of the surface without needing further sample preparation. High spatial resolution (i.e. lateral and vertical) can be achieved providing opportunities for in-depth profiling and microanalysis (e.g, identification of individual mineral grains by means of elemental composition). Additionally, the detection of trace elements, namely rare earth element fractionation patterns, can provide further information on the nature of planetary formation and differentiation. Knowledge of the isotopic composition, including the use of...