( All ( ( meteorites ( unaffected ( by ( weathering ( ( have ( a ( ( ( thin and ) well-defined ) ( black ( fusion crust ) ) ) ) ) ( formed ( by ( ( frictional heating ) ( in ( the atmosphere ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT All)) (VP (VBZ meteorites) (ADJP (JJ unaffected) (PP (IN by) (S (VP (VBG weathering) (VP (VB have) (NP (DT a) (ADJP (JJ thin) (CC and) (JJ well-defined)) (JJ black) (NN fusion) (NN crust)) (VP (VBN formed) (PP (IN by) (NP (NP (JJ frictional) (NN heating)) (PP (IN in) (NP (DT the) (NN atmosphere)))))))))))) (. .)))
All meteorites unaffected by weathering have a thin and well-defined black fusion crust formed by frictional heating in the atmosphere.
(ROOT (S (NP (NP (NN Uneven) (NN heating)) (PP (IN of) (NP (DT the) (NN atmosphere)))) (VP (VBP form) (NP (NN weather) (NNS patterns))) (. .)))