"Scientists have presented evidence that desert heat, a little water, and meteorite impacts may have been enough to cook up one of the first prerequisites for life: The dominance of "left-handed" amino acids, the building blocks of life on this planet.
In a report at the 235th national meeting of the American Chemical Society, Ronald Breslow, Ph.D., University Professor, Columbia University, and former ACS President, described how our amino acid signature came from outer space."

Read more (http://www.machineslikeus.com/cms/news/meteorites-delivered-seeds-earth-s-left-hand-life)

hey blob, why do they HAVE to be lefthanded? why couldnt right handed AA work as well???????

Virtually all life uses left handed amino acids, as opposed to right handed ones. Assuming that in the beginning, life started using left handed amino acids, then their experiment had to show that abiotic processes led to the optic enantiomer.

why do they HAVE to be lefthanded?

Hum,
Indeed,
they don't have to be left handed.
But, the early solar system was bathed in polarising radiation that allowed the creation of more left handed molecules.
And those molecules bombarded the young earth - and in turn, when life arose it it was more likely to be the left handed variety.

So what is the source of these left handed amino acids?

Raptor Jesus.