Photo taken on Dec. 22, 2019 shows an iceberg in the Cosmonaut Sea. During China's 36th Antarctic expedition, China's first domestically made polar icebreaker Xuelong 2 has to overcome various difficulties including colliding with icebergs. (Xinhua/Liu Shiping)

Photo taken on Dec. 28, 2019 shows icebergs in the Cosmonaut Sea. During China's 36th Antarctic expedition, China's first domestically made polar icebreaker Xuelong 2 has to overcome various difficulties including colliding with icebergs. (Xinhua/Liu Shiping)

Photo taken on Dec. 27, 2019 shows icebergs in the Cosmonaut Sea. During China's 36th Antarctic expedition, China's first domestically made polar icebreaker Xuelong 2 has to overcome various difficulties including colliding with icebergs. (Xinhua/Liu Shiping)

Photo taken on Dec. 18, 2019 shows an iceberg in the Cosmonaut Sea. During China's 36th Antarctic expedition, China's first domestically made polar icebreaker Xuelong 2 has to overcome various difficulties including colliding with icebergs. (Xinhua/Liu Shiping)

Photo taken on Dec. 11, 2019 shows an iceberg in the Cosmonaut Sea. During China's 36th Antarctic expedition, China's first domestically made polar icebreaker Xuelong 2 has to overcome various difficulties including colliding with icebergs. (Xinhua/Liu Shiping)

Photo taken on Dec. 27, 2019 shows an iceberg in the Cosmonaut Sea. During China's 36th Antarctic expedition, China's first domestically made polar icebreaker Xuelong 2 has to overcome various difficulties including colliding with icebergs. (Xinhua/Liu Shiping)

Photo taken on Dec. 16, 2019 shows an iceberg in the Cosmonaut Sea. During China's 36th Antarctic expedition, China's first domestically made polar icebreaker Xuelong 2 has to overcome various difficulties including colliding with icebergs. (Xinhua/Liu Shiping)

Photo taken on Dec. 27, 2019 shows an iceberg in the Cosmonaut Sea. During China's 36th Antarctic expedition, China's first domestically made polar icebreaker Xuelong 2 has to overcome various difficulties including colliding with icebergs. (Xinhua/Liu Shiping)

Photo taken on Dec. 20, 2019 shows an iceberg in the Cosmonaut Sea. During China's 36th Antarctic expedition, China's first domestically made polar icebreaker Xuelong 2 has to overcome various difficulties including colliding with icebergs. (Xinhua/Liu Shiping)