Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists find that Earth and Mars are different to the core

29.06.2007
Research comparing silicon samples from Earth, meteorites and planetary materials, published in Nature (28th June 2007), provides new evidence that the Earth’s core formed under very different conditions from those that existed on Mars. It also shows that the Earth and the Moon have the same silicon isotopic composition supporting the theory that atoms from the two mixed in the early stages of their development.

This latest research which was carried out by scientists from Oxford University along with colleagues from University of California, Los Angeles (UCLA) and the Swiss Federal Institute of Technology in Zurich (ETH) compared silicon isotopes from rocks on Earth with samples from meteorites and other solar system materials. This is the first time that isotopes have been used in this way and it has opened up a new line of scientific investigation into how the Earth’s core formed.

On Earth rocks that make up volcanoes and mountain ranges and underlie the ocean floor are made of silicate – compounds made of silicon and oxygen linked with other kinds of atoms. Silicate dominates down to a depth of 2,900 km – roughly half way to the centre of the Earth. At this point there is an abrupt boundary with the dense metallic iron core. Studies by Birch in the 1950’s demonstrated that the outer core had a density too low to be made of pure iron and that it must also be made up of some lighter elements (see notes to editors for further details).

Research team member, Bastian Georg, a post doctoral researcher from Oxford University’s Earth Sciences Department said, “We dissolved meteorites, provided by the Natural History Museum in London, in order to compare their isotopic composition with those of rocks from the Earth. The silicon was separated from other elements and the atomic proportions of isotopes measured using a particularly sophisticated mass spectrometer at the ETH in Zurich”.

Professor Alex Halliday, also from Oxford University explains, “We were quite startled at our results which showed that the heavier isotopes from silicate Earth samples contained increased proportions of the heavier isotopes of silicon. This is quite different from meteorites from the silicate portions of Mars and the large Asteroid Vesta – which do not display such an effect even though these bodies also have an iron core.”

Silicate samples from Mars and Vesta are identical to a primitive class of meteorites called chondrites that represent average solar system material from small “planetesimals” that never underwent core formation.

Professor Halliday continues, “The most likely explanation is that, unlike Mars and Vesta, the Earth’s silicon has been divided into two sorts – a portion that became a light element in the Earth’s core dissolved in metal and the greater proportion which formed the silicon-oxygen bonded silicate of the Earth’s mantle and crust.”

At depths the silicates change structure to denser forms so the isotopic make-up would depend on the pressure at which metal and silicate separate. Quantifying this effect is the subject of ongoing studies. Co-author on the paper Edwin Schauble from UCLA, has produced preliminary calculations that show that the isotopic effects found are of the right direction and magnitude.

This research provides new evidence that the Earth’s core formed under different conditions from those that existed on Mars. This could be explained in part by the difference in mass between the two planets. With Earth being eight times larger than Mars the pressure of core formation could be higher and different silicate phases may have been involved. The mass of a planet also affects the energy that is released as it accretes (or grows).

The Earth accreted most of its mass by violent collisions with other planets and planetary embryos. The bigger the planet, the greater the gravitational attraction and the higher the temperatures that are generated as the kinetic energy of impacting objects is converted to heat. Some have proposed that the outer Earth would have periodically become a “magma ocean” of molten rock as a result of such extreme high temperature events.

There is evidence that Mars stopped growing in the first few million years of the solar system and did not experience the protracted history of violent collisions that affected the Earth. There already exists compelling evidence for relatively strong magnetic fields early in martian history but a thorough understanding of the martian core must await geophysical measurements by future landers. It is however thought that the core of Mars is proportionally smaller than that of the Earth and it probably formed under lower pressures and temperatures.

The research also shows that the Moon has the same silicon isotopic composition as the Earth. This cannot be caused by high pressure core formation on the Moon which is only about one percent of the mass of the Earth. However, it is consistent with the recent proposal that the material that made the Moon during the giant impact between the proto-Earth and another planet, usually called “Theia”, was sufficiently energetic that the atoms of the disk from which the Moon formed mixed with those from the silicate Earth. This means the silicon in the silicate Earth must have already had a heavy isotopic composition before the Moon formed about 40 million years after the start of the solar system.

The research was supported from grants provided by the UK’s Science and Technology Facilities Council, and the USA’s and Switzerland’s National Science Foundation.

Contacts
Gill Ormrod – Science and Technology Facilities Council Press Office
Tel: 01793 442012. Email: gill.ormrod@stfc.ac.uk
Pete Wilton – Oxford University Press Office
Tel: 01865 283877
Email : pete.wilton@admin.ox.ac.uk
UK Science contact
Professor Alex Halliday – Department of Earth Science, Oxford University
Tel: 07769728153
Email: alexh@earth.ox.ac.uk

Gill Ormrod | alfa
Further information:
http://www.stfc.ac.uk

More articles from Earth Sciences:

nachricht Clear as mud: Desiccation cracks help reveal the shape of water on Mars
20.04.2018 | Geological Society of America

nachricht Hurricane Harvey: Dutch-Texan research shows most fatalities occurred outside flood zones
19.04.2018 | European Geosciences Union

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Magnetic nano-imaging on a table top

20.04.2018 | Physics and Astronomy

Start of work for the world's largest electric truck

20.04.2018 | Interdisciplinary Research

Atoms may hum a tune from grand cosmic symphony

20.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>