6 research outputs found
Terrestrial exposure of a fresh Martian meteorite causes rapid changes in hydrogen isotopes and water concentrations
Determining the hydrogen isotopic compositions and H2O contents of meteorites and their components is important for addressing key cosmochemical questions about the abundance and source(s) of water in planetary bodies. However, deconvolving the effects of terrestrial contamination from the indigenous hydrogen isotopic compositions of these extraterrestrial materials is not trivial, because chondrites and some achondrites show only small deviations from terrestrial values such that even minor contamination can mask the indigenous values. Here we assess the effects of terrestrial weathering and contamination on the hydrogen isotope ratios and H2O contents of meteoritic minerals through monitored terrestrial weathering of Tissint, a recent Martian fall. Our findings reveal the rapidity with which this weathering affects nominally anhydrous phases in extraterrestrial materials, which illustrates the necessity of sampling the interiors of even relatively fresh meteorite falls and underlines the importance of sample return missions
A Global Fireball Observatory
The world's meteorite collections contain a very rich picture of what the
early Solar System would have been made of, however the lack of spatial context
with respect to their parent population for these samples is an issue. The
asteroid population is equally as rich in surface mineralogies, and mapping
these two populations (meteorites and asteroids) together is a major challenge
for planetary science. Directly probing asteroids achieves this at a high cost.
Observing meteorite falls and calculating their pre-atmospheric orbit on the
other hand, is a cheaper way to approach the problem. The Global Fireball
Observatory (GFO) collaboration was established in 2017 and brings together
multiple institutions (from Australia, USA, Canada, Morocco, Saudi Arabia, the
UK, and Argentina) to maximise the area for fireball observation time and
therefore meteorite recoveries. The members have a choice to operate
independently, but they can also choose to work in a fully collaborative manner
with other GFO partners. This efficient approach leverages the experience
gained from the Desert Fireball Network (DFN) pathfinder project in Australia.
The state-of-the art technology (DFN camera systems and data reduction) and
experience of the support teams is shared between all partners, freeing up time
for science investigations and meteorite searching. With all networks combined
together, the GFO collaboration already covers 0.6% of the Earth's surface for
meteorite recovery as of mid-2019, and aims to reach 2% in the early 2020s. We
estimate that after 5 years of operation, the GFO will have observed a fireball
from virtually every meteorite type. This combined effort will bring new,
fresh, extra-terrestrial material to the labs, yielding new insights about the
formation of the Solar System.Comment: Accepted in PSS. 19 pages, 9 figure
Origin and age of the earliest Martian crust from meteorite NWA 7533
The ancient cratered terrain of the southern highlands of Mars is thought to hold clues to the planet’s early differentiation [1,2] but until now no meteoritic regolith breccias have been recovered from Mars. Here we show that the meteorite Northwest Africa (NWA) 7533 (paired with meteorite NWA 7034 [3]) is a polymict breccia consisting of a fine-grained interclast matrix containing clasts of igneous-textured rocks and fine-grained clast-laden impact melt rocks. High abundances of meteoritic siderophiles (for example nickel and iridium) found throughout the rock reach a level in the fine-grained portions equivalent to 5 per cent CI chondritic input, which is comparable to the highest levels found in lunar breccias. Furthermore, analyses of three leucocratic monzonite clasts show a correlation between nickel, iridium and magnesium consistent with differentiation from impact melts. Compositionally, all the fine-grained material is alkalic basalt, chemically identical (except for sulphur, chlorine and zinc) to soils from Gusev crater. Thus, we propose that NWA 7533 is a Martian regolith breccia. It contains zircons for which we measured an age of 4,428 ± 25 million years, which were later disturbed 1,712 ± 85 million years ago. This evidence for early crustal differentiation implies that the Martian crust, and its volatile inventory [4] formed in about the first 100 million years of Martian history, coeval with earliest crust formation on the Moon [5] and the Earth [6]. In addition, incompatible element abundances in clast-laden impact melt rocks and interclast matrix provide a geochemical estimate of the average thickness of the Martian crust (50 kilometres) comparable to that estimated geophysically [2,7]