BBC Homepage World Service Education
BBC Homepagelow graphics version | feedback | help
BBC News Online
 You are in: Sci/Tech
Front Page 
World 
UK 
UK Politics 
Business 
Sci/Tech 
Health 
Education 
Entertainment 
Talking Point 
In Depth 
AudioVideo 

Wednesday, 12 July, 2000, 17:56 GMT 18:56 UK
'Fossil air' provides climate clues
Namib Nasa
Sulphur-rich rocks in the Namib Desert
By BBC News Online science editor Dr David Whitehouse

Scientists have extracted samples of Earth's atmosphere trapped in rocks millions of years old.

It is a technique that could provide new data about past climate upheavals and mass extinctions.

Until now, the oldest samples of "fossil air" have come from ice cores from the central Greenland ice cap. They provide evidence for the past 400,000 years.

To go back further, scientists have to analyse rocks that have acquired some recognisable chemical signature through interaction with the ancient atmosphere during their formation.

Huiming Bao, of the University of California San Diego, La Jolla, US, and colleagues, have shown that just such a signature can be found in some sulphate rocks.

These retain the distinctive pattern of the different types, or isotopes, of oxygen that existed much earlier in Earth's history

The pattern, or ratio, of isotopes was locked into the minerals when the oxygen reacted with molten rock on the planet's surface.

Mars lander

This isotopic pattern is affected by the amount of ozone present in the ancient atmosphere and hence may serve as a monitor of atmospheric conditions in the past.

The rocks they studied came from the United States and Africa and were formed in the Miocene geological epoch.

This period extended from 23.7 to 5.3 million years ago. It was a time when the great mountain ranges of Europe, Asia and America were forming.

The team examined sulphur-rich rocks from the Namib desert in Africa and volcanic-ash-beds from the western United States.

The researchers say that their new technique is a promising way to explore changes in the Earth's atmosphere in the past.

They add that it may also be a new way to analyse rocks from Mars, as the Pathfinder Mars Lander showed that some rocks contain high quantities of Sulphur.

The research is published in the journal Nature.

Search BBC News Online

Advanced search options
Launch console
BBC RADIO NEWS
BBC ONE TV NEWS
WORLD NEWS SUMMARY
PROGRAMMES GUIDE
See also:

12 Jul 99 | Sci/Tech
Sahara desert born 4,000 years ago
05 Aug 99 | Sci/Tech
The bacteria that changed the Earth
18 Aug 99 | Sci/Tech
Ships' sulphur fuels climate change
10 Sep 99 | Sci/Tech
Climate disaster possible by 2100
Internet links:


The BBC is not responsible for the content of external internet sites

Links to more Sci/Tech stories are at the foot of the page.


E-mail this story to a friend

Links to more Sci/Tech stories