New proof that Museum meteorite comes from Mars

11 October 2012

New research on the Natural History Museum’s Tissint meteorite reveals evidence of its Martian origin, scientists report in the journal Science today.

Museum scientist Dr Caroline Smith holds the newly arrived Tissint Martian meteorite

Museum scientist Dr Caroline Smith holds the Tissint meteorite. It is now the largest Martian meteorite in the Natural History Museum collections.

The Tissint meteorite came from the Martian crust and contains traces of Mars’ atmosphere and surface alteration, according to the international team, led by Prof Hasnaa Chennaoui Aoudjehane from the Hassan II University, Morocco, and including the Natural History Museum’s meteorite expert Dr Caroline Smith.

These chemical clues highlight the importance of this rare meteorite for studying Mars here on Earth - something that will complement discoveries from robotic missions such as NASA's Curiosity rover.

The Tissint meteorite fell to Earth in Morocco in July 2011. The largest fragment was used in this study and is on display at the Museum. 

Black glass inside the Tissint meteorite (image about 2mm across)

Black glass inside the Tissint meteorite (less than 2mm)

Martian meteorites are incredibly rare, and this one was recovered soon after it fell, reducing the likelihood of contamination and offering a purer insight into the Red Planet.

Black glass

The team analysed the meteorite and found black glass inside it, which is formed when the surrounding rock and minerals melt during a high-shock event, such as when a meteorite is blasted off the surface of its parent body by a large impact.

The black glass contains elements not found in the surrounding rock, including a different type (isotope) of nitrogen. The team's measurements show that the nitrogen isotope signature is characteristic of Mars' atmosphere.

The black glass is enriched with other elements, such as cerium, which also leave behind a Martian chemical signature.

The team think that these enrichments result from the formation of minerals, deposited from fluids during weathering processes on Mars. This happened when fluids on Mars picked up elements from the Martian soil. As the fluid flowed through the Martian crust, it deposited minerals (enriched in the leached elements) in cracks and fissures.

'When the rock suffered the large shock, the black glass was formed along the cracks and fissures, where the weathering products were concentrated,' said Smith.

The planet Mars. It's our closest neighbour.

The planet Mars. It's our closest Earth-like planet and many of its rocks are similar to Earth's.

'The nitrogen isotopic composition reveals that this shock event also trapped a component of the Martian atmosphere.'

'So, the black glass retains the chemical fingerprint or signature which is characteristic of the Martian surface and atmosphere.'

'We have conclusively shown, for the first time in a meteorite, the chemical signatures of weathering processes on Mars,' said Chennaoui Aoudjehane.

Smith adds, 'This opens up a new window on the Martian environment that we've never had before. 

'We have an idea of the composition and chemistry of the Martian surface and atmosphere from robotic missions such as the NASA Viking and MER missions and ESA’s Mars Express, but we can actually measure the same components in a Martian sample using our high-precision instruments in laboratories on Earth’.

'It's a great example of how our world-class collection and cutting-edge technology is fuelling a rich programme of research into the evolution of the solar system.'

Future studies

'We are continuing to study Tissint both here at the Museum and with samples from our collection that we are providing to colleagues around the world,' concludes Smith. 

'We are in the process of using some very innovative scientific techniques and instrumentation and we have already had some tantalising initial results. We're very much looking forward to unlocking even more secrets that this exciting rock holds'.

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