Ammonia brought to Earth by meteorites could have helped kick-start life, says a team at Arizona State University.
Scientists led by research professor Sandra Pizzarello found large amounts of ammonia in a primitive Antarctic asteroid. This, they say, could have provided a sustained source of reduced nitrogen essential to the chemistry of life's information transfer and catalytic processes.
"All origins-of-life theories need to account for a sustained source of reduced nitrogen in order to make amino acids and nucleobases," says Pizzarello.
It was at one time thought that the early Earth had abundant ammonia caused by the reducing atmosphere. However, current geochemical evidence of a neutral early Earth atmosphere, combined with the way ammonia is known to be destroyed by sunlight, has left scientists struggling to account for a constant supply.
The team found that the Graves Nunataks (GRA) 95229 asteroid, discovered in 1995, released ammonia under high temperatures and in the presence of water - the conditions to which it would have been subjected when it hit Earth.
They found that it released ammonia representing about one percent of its mass. Enough such meteorites, they say, could have supplied plenty of ammonia for nitrogen formation.
"An abundant exogenous delivery of ammonia, therefore, might have been significant in aiding early Earth's molecular evolution," they say.