Photo shows China's first domestically-built polar research vessel and icebreaker "Xuelong 2" in Shanghai, east China, Sept. 10, 2018. "Xuelong 2" was launched on Monday in Shanghai. (Photos: Liu Shiping/ Xinhua)

Photo shows China's first domestically-built polar research vessel and icebreaker "Xuelong 2" in Shanghai, east China, Sept. 10, 2018. "Xuelong 2" was launched on Monday in Shanghai.

Photo shows China's first domestically-built polar research vessel and icebreaker "Xuelong 2" in Shanghai, east China, Sept. 10, 2018. "Xuelong 2" was launched on Monday in Shanghai.

Photo shows China's first domestically-built polar research vessel and icebreaker "Xuelong 2" in Shanghai, east China, Sept. 10, 2018. "Xuelong 2" was launched on Monday in Shanghai.