Search results for "Meteori"

Zr- Hf Fractionation During Water-Rock Interaction

2017

International audience; Zr and Hf are two elements having same ionic charge and similar ionic size at a given coordination number. Despite the Zr/Hf ratio is considered to be quite constant in meteorites and lithospheric rocks, seawaters collected from the surface down to varying depths of several Pacific Ocean stations reveal that the Zr/Hf ratio increases by one order of magnitude. Very recent studies have shown that, in both ground waters and lake waters, the Zr/Hf ratio is either higher or lower compared to the interacting minerals displaying a large variability in the distribution of these twin elements. In this communication the possible processes responsible for such a large fraction…

Zvaigžņotā Debess: 1963, Ziema - Rudens

1963

Ir vai nav meteorīts?

2020

Buklets "Ir vai nav meteorīts?" dod sistematizētu informāciju par meteorītiem un tiem līdzīgajiem veidojumiem, to iedalījumu un tipiem, kā arī skaidro atrasto Latvijā nokritušo meteorītu īpatnības. Bukletu ilustrē Latvijas Universitātes Muzeja kolekciju paraugu fotogrāfijas.

Nickel on Mars: Constraints on meteoritic material at the surface

2006

[1] Impact craters and the discovery of meteorites on Mars indicate clearly that there is meteoritic material at the Martian surface. The Alpha Particle X-ray Spectrometers (APXS) on board the Mars Exploration Rovers measure the elemental chemistry of Martian samples, enabling an assessment of the magnitude of the meteoritic contribution. Nickel, an element that is greatly enhanced in meteoritic material relative to samples of the Martian crust, is directly detected by the APXS and is observed to be geochemically mobile at the Martian surface. Correlations between nickel and other measured elements are used to constrain the quantity of meteoritic material present in Martian soil and sedimen…

Weathering of Fe-bearing minerals under Martian conditions, investigated by Mössbauer spectroscopy

2004

Abstract The surface of Mars is covered by weathered material. Mars' rusty red colour in particular is commonly ascribed to ferric iron-bearing minerals. The planet's surface is generally iron rich. Mossbauer spectroscopy is a powerful tool for quantitative mineralogical analysis of Fe-bearing minerals. Consequently, the miniaturized Mossbauer spectrometer MIMOS II is part of the payload of NASA's twin Mars Exploration Rovers “Spirit” and “Opportunity”, and ESA's ill-fated Mars Express lander “Beagle 2”. Both Mars Exploration Rovers are currently conducting successful surface operations on Mars. In this paper, we give a brief insight into mission operations with respect to the reconstructio…

Identification of carbonate-rich outcrops on Mars by the Spirit rover.

2010

Ancient Carbonate Minerals on Mars The historical presence of liquid water on Mars together with a CO 2 -rich atmosphere should have resulted in the accumulation of large deposits of carbonate minerals. Yet, evidence for the presence of carbonates on the surface of Mars has been scarce. Using data collected by the Mars Exploration Rover, Spirit, Morris et al. (p. 421 , published online 3 June; see the Perspective by Harvey ) now present evidence for carbonate-rich outcrops in the Comanche outcrops within the Gusev crater. The carbonate is a major outcrop component and may have formed in the Noachian era (∼4 billion years ago) by precipitation from hydrothermal solutions that passed through …

Isotopic composition of the precipitations in the central Mediterranean: Origin marks and orographic precipitation effects

2006

The isotopic composition of the rainfall in northwestern Sicily (Italy, central Mediterranean) was investigated in the period February 2002 to March 2003. A rain gauge network was installed and sampled monthly. The monthly values of the D and 18O ratios showed a wide range that reflected seasonal climatic variations. Mean weighted values were used to define an isotopic model of precipitation. Temporal variations in deuterium excess were also investigated. Using mean volume weighted values, the Local Meteoric Water Line (LMWL) can be represented by the equation: δD = 4.7δ18O - 8.2 (r2 = 0.96). Deuterium excess (d = δD - 8δ18O) was found to be strongly related to orography. The coastline samp…

Evidence for mechanical and chemical alteration of iron-nickel meteorites on Mars: Process insights for Meridiani Planum

2011

The weathering of meteorites found on Mars involves chemical and physical processes that can provide clues to climate conditions at the location of their discovery. Beginning on sol 1961, the Opportunity rover encountered three large iron meteorites within a few hundred meters of each other. In order of discovery, these rocks have been assigned the unofficial names Block Island, Shelter Island, and Mackinac Island. Each rock presents a unique but complimentary set of features that increase our understanding of weathering processes at Meridiani Planum. Significant morphologic characteristics interpretable as weathering features include (1) a large pit in Block Island, lined with delicate iro…

Mineralogy and chemistry of cobbles at Meridiani Planum, Mars, investigated by the Mars Exploration Rover Opportunity

2010

Numerous loose rocks with dimensions of a few centimeters to tens of centimeters and with no obvious physical relationship to outcrop rocks have been observed along the traverse of the Mars Exploration Rover Opportunity. To date, about a dozen of these rocks have been analyzed with Opportunity’s contact instruments, providing information about elemental chemistry (Alpha Particle X‐ray Spectrometer), iron mineralogy and oxidation states (Mossbauer Spectrometer) and texture (Microscopic Imager). These "cobbles" appear to be impact related, and three distinct groups can be identified on the basis of chemistry and mineralogy. The first group comprises bright fragments of the sulfate‐rich bedroc…

New insights into the mineralogy and weathering of the Meridiani Planum meteorite, Mars

2011

– Meridiani Planum is the first officially recognized meteorite find on the surface of Mars. It was discovered at and named after the landing site of the Mars Exploration Rover Opportunity. Based on its composition, it was classified as a IAB complex iron meteorite. Mossbauer spectra obtained by Opportunity are dominated by kamacite (α-Fe-Ni) and exhibit a small contribution of ferric oxide. Several small features in the spectra have been neglected to date. To shed more light on these features, five iron meteorite specimens were investigated as analogs to Meridiani Planum with a laboratory Mossbauer setup. Measurements were performed on (1) their metallic bulk, (2) troilite (FeS) inclusions…