Question: when did exploration to the inner solar system begin
[{'answer': '1959', 'provenance': [{'wikipedia_id': '19327051', 'title': 'Discovery and exploration of the Solar System', 'start_paragraph_id': 19, 'start_character': 214, 'end_paragraph_id': 19, 'end_character': 218, 'bleu_score': 1.0, 'section': 'Section::::Observations by spacecraft.\n'}]}, {'provenance': [{'wikipedia_id': '19327051', 'title': 'Discovery and exploration of the Solar System', 'start_paragraph_id': 21, 'start_character': 0, 'end_paragraph_id': 21, 'end_character': 414, 'bleu_score': 0.8770359524899021, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 14936700989088312203}, 'section': 'Section::::Observations by spacecraft.:Flybys.\n'}]}]