Question: what is the atmosphere of europa made of
[{'answer': 'primarily of oxygen', 'provenance': [{'wikipedia_id': '43127', 'title': 'Europa (moon)', 'start_paragraph_id': 2, 'start_character': 178, 'end_paragraph_id': 2, 'end_character': 197, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '43127', 'title': 'Europa (moon)', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 431, 'bleu_score': 0.866872903843085, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4639698625624389661}, 'section': 'Section::::Abstract.'}]}]