Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Meteorites from inner Solar System match up to Earth's plantinum standard

22.09.2008
Some of the world’s rarest and most precious metals, including platinum and iridium, could owe their presence in the Earth’s crust to iron and stony-iron meteorites, fragments of a large number of asteroids that underwent significant geological processing in the early Solar System.

Dr Gerhard Schmidt from the University of Mainz, Germany, has calculated that about 160 metallic asteroids of about 20 kilometres in diameter would be sufficient to provide the concentrations of these metals, known as Highly Siderophile Elements (HSE), found in the Earth’s crust. Dr Schmidt will be presenting his findings at the European Planetary Science Congress in Münster on Monday 22nd September.

Dr Schmidt said, “A key issue for understanding the origin of planets is the knowledge of the abundances of HSE in the crust and mantle of the Earth, Mars and the Moon. We have found remarkably uniform abundance distributions of HSE in our samples of the Earth’s upper crust. A comparison of these HSE values with meteorites strongly suggests that they have a cosmochemical source.”

During a 12-year study, Dr Schmidt and colleagues have analysed the concentrations of HSE at meteorite impact sites around the world, as well as in the samples from the Earth’s mantle and crust. In addition, he has compared the data from the Earth with data from impact breccias from the Moon brought by the Apollo missions and Martian meteorites, believed to be samples from the mantle and crust on Mars.

Although HSE were present in the nebula from which the Earth formed, as the young planet evolved and heated up they were stripped, along with other heavy elements, from the silicate mantle into the iron and nickel-rich metallic core. The presence of HSE in the mantle is still a matter of debate. However, a widely accepted theory is that HSE were added by meteorite impacts as a veneer of material over the Earth’s surface after the core had formed, about 20-30 million years after the planet’s accretion. This could have been by the collision with a Mars-sized impactor that led to the formation of the Moon. Different classes of meteorites have characteristic elemental ratios of HSE that give indications where in the Solar System they formed. However, the characteristic ratios of HSEs in the Earth’s upper mantle (for example the ruthenium/iridium element ratio of about 2) match up with theoretical predictions for asteroids formed in the Mercury-Venus region.

The Earth is a differentiated body, with a iron-nickel core, a silicate mantle, and evolved silicate crust. Dr Schmidt’s study shows that the abundance ratios of HSE in the Earth’s crust are much higher than those found in stony meteorites, known as chondrites, which represent the pristine material from the early Solar System. The ratios of HSE found in the crust bear a much closer resemblance to iron or stony-iron meteorites. These are fragments of larger asteroids that have had enough internal heat in the past to form a molten metal core. The HSE concentrate preferentially in the liquid core and at the boundary with the solid, rocky envelope. However, the exact ratios of the different metals depend on the physical conditions under which they were formed.

The ratios of HSE found in the Earth’s upper mantle do not exactly match any specimens of meteorites found in collections around the world. Close to the mantle highly siderophile element ratios are data from the iron meteorite Charlotte.

To date, about 20 iron meteorites and about 20 stony meteorites, called chondrites, have been identified as projectiles of the 175 known impact craters on Earth. The projectiles for the other 135 impact craters on Earth are still unknown. No meteorites have been identified as being formed in the region between Mercury and Venus.

Intriguingly, some of the Martian meteorites which are probably most representative of the Martian crust also have HSE values that resemble groups of iron meteorites and stony irons, suggesting that a similar process took place on Mars.

Dr Schmidt said “The first meteorite to be found on Mars was an iron meteorite, discovered by the Opportunity rover in January 2005. Analysis of the Nahkla, Shergotty and Zagami Martian meteorites strongly supports a genetic link with certain iron meteorites and pallasites.”

FURTHER INFORMATION

Highly Siderophile Elements (HSE)
Siderophile (iron-loving) elements are a group of high-density transition metals that tend to bond with metallic iron in the solid or molten state. The HSE group includes rhenium (Re), osmium Os), iridium (Ir), ruthenium (Ru), rhodium (Rh), platinum (Pt), palladium (Pd) and gold (Au).
EUROPEAN PLANETARY SCIENCE CONGRESS
EPSC 2008 is organised by Europlanet, the European Planetology Network in association with the European Geosciences Union and the Westfälische Wilhelms Universität, Münster.
For further details, see the meeting website:
http://meetings.copernicus.org/epsc2008/
EUROPLANET
EuroPlaNet co-ordinates activities in Planetary Sciences in order to achieve a long-term integration of this discipline in Europe.
The objectives are to:
1) increase the productivity of planetary projects with European investment, with emphasis on major planetary exploration missions;
2) initiate a long-term integration of the European planetary science community;
3) improve European scientific competitiveness, develop and spread expertise in this research area;

4) improve public understanding of planetary environments.

Europlanet Project website: http://europlanet.cesr.fr/
Europlanet Outreach website: http://www.europlanet-eu.org
Information films on Europlanet can be found at:
http://www.youtube.com/watch?v=5Bn_lhDXWSA
http://www.youtube.com/watch?v=mcEtDuGOmAQ
IMAGES
Iron meteorite on the surface of Mars, as imaged by the Mars Exploration Rover Opportunity

http://photojournal.jpl.nasa.gov/catalog/PIA07269

Artist’s impression of the metallic asteroid, Kleopatra
http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=4565
Artist’s impression of asteroid impact with early Earth that led to lunar formation

http://esamultimedia.esa.int/images/smart_1/img08.jpg

Anita Heward | alfa
Further information:
http://www.europlanet-eu.org
http://europlanet.cesr.fr/

More articles from Physics and Astronomy:

nachricht Electrocatalysis can advance green transition
23.01.2017 | Technical University of Denmark

nachricht Quantum optical sensor for the first time tested in space – with a laser system from Berlin
23.01.2017 | Ferdinand-Braun-Institut Leibniz-Institut für Höchstfrequenztechnik

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Quantum optical sensor for the first time tested in space – with a laser system from Berlin

For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.

According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Efficient time synchronization of sensor networks by means of time series analysis

24.01.2017 | Information Technology

Immune Defense Without Collateral Damage

24.01.2017 | Life Sciences

Open, flexible assembly platform for optical systems

24.01.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>