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1·After several years of painstaking research and debate, NASA scientists whittled down their initial list of over 50 sites to four - Eberswalde Crater, Holden Crater, Mawrth Vallis, and Gale Crater.

在经过好几年的刻苦研究和讨论以后，NASA的科学家已经将他们一开始的50多个登陆点削减到了4个，它们分别是：埃伯斯·沃德环形山、霍尔登环形山、马沃斯山谷以及盖尔环形山。

2·After several years of painstaking research and debate, NASA scientists whittled down their initial list of over 50 sites to four — Eberswalde Crater, Holden Crater, Mawrth Vallis, and Gale Crater.

在经过好几年的刻苦研究和讨论以后，NASA的科学家已经将他们一开始的50多个登陆点削减到了4个，它们分别是：埃伯斯·沃德环形山、霍尔登环形山、马沃斯山谷以及盖尔环形山。