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Planet Neptune

South Polar Cap

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Planet Neptune South Polar Cap

Triton's surface is covered with nitrogen and methane ice. Its surface temperature is a mere 38 degrees Celsius above absolute zero. Dark streaks across the south polar cap may be the result of recent geyser-like eruptions of gas, dust, and ice venting from beneath the cap into the satellite's near-vacuum atmosphere. The diameter of Triton is 2700 km (1674 mi).