technology-news

How life on Earth evolved 2.4 b yrs ago when sun was 25 pc weaker

Washington, Oct. 5 : Scientists have ruled out a theory as to why Earth was warm enough to sustain the planet's earliest life forms when the Sun's energy was roughly three-quarters the strength it is today.


Life evolved on Earth during the Archean, between 3.8 and 2.4 billion years ago, but the weak Sun should have meant the planet was too cold for life to take hold at this time; scientists have therefore been trying to find an explanation for this conundrum, what is dubbed the 'faint, young Sun paradox.'

Study author, Dr Ray Burgess, from Manchester's School of Earth, Atmospheric and Environmental Sciences, said that during the Archean the solar energy received at the surface of the Earth was about 20 to 25 percent lower than present.

Burgess said that if the greenhouse gas composition of the atmosphere was comparable to current levels then the Earth should have been permanently glaciated but geological evidence suggests there were no global glaciations before the end of the Archean and that liquid water was widespread.

Lead author Professor Bernard Marty, from the CRPG-CNRS University of Lorraine, said that to counter the effect of the weaker Sun, carbon dioxide concentrations in the Earth's atmosphere would need to have been 1,000 times higher than present.

Marty asserted that however, ancient fossil soils - the best indicators of ancient carbon dioxide levels in the atmosphere - suggest only modest levels during the Archean.

He said that other atmospheric greenhouse gases were also present, in particular ammonia and methane, but these gases are fragile and easily destroyed by ultraviolet solar radiation, so are unlikely to have had any effect.

But another climate-warming theory - one the team wanted to test - is that the amount of nitrogen could have been higher in the ancient atmosphere, which would amplify the greenhouse effect of carbon dioxide and allow the Earth to remain ice-free.

The new study has been published in the journal Science.

--ANI (Posted on 05-10-2013)

technology-news headlines

Fossil of 325-million-year-old shark-like specie sheds light on evolution of jaws

Soon, wireless power zones to charge your phone

Soon, cheap computers and 'throwaway' cell phones

Scientists identify target for treating dengue

Waste sulphur to produce cheap infra-red devices

When meteors delivered vitamin B3 at your doorstep!

Believe it! These females have penises

How dust affects light reaching us from stars

Meteorites unlock secrets of Mars' early atmosphere

How brain regions develop as our ability to store memories improves

Soon, robots that are able to form 'swarms' without using any memory

How ice ages actually came about

Quick Links: Goa | Munnar | Pondicherry | Free Yearly Horoscope '2014

Comments

Your e-mail:


Your Full Name:


Type verification image:
verification image, type it in the box

Message:

Back to Top