00:00 11 March 2009 The burgeoning field of astrobiology has a
less well-known offshoot right here on Earth: the search for a
"shadow biosphere" - a second, independent form of life
unrelated to the sort we know Image 3 of 6 One promising avenue
for discovering a new form of life is to look for "mirror life".
Normal organisms use right-handed sugars and left-handed amino
acids , but there is no theoretical reason why an alternative
form of life could not use their mirror-image equivalents. Such
mirror life would almost certainly be microbial, as otherwise we
would probably have discovered it already. These images show the
most common form (left) and the L isomer (right) of isoleucine ,
an amino acid. (Images: Wikimedia Commons)