ATMOSPHERE Mercury's atmosphere is extremely thin and composed mostly of oxygen, sodium, hydrogen, and helium. Due to its proximity to the sun and weak gravity, the solar wind strips away its atmosphere. Surface temperatures fluctuate wildly, ranging from -290°F (-180°C) to 800°F (430°C) due to its lack of atmosphere to retain heat. This extreme temperature variation and the absence of a substantial atmosphere make Mercury's environment inhospitable for sustaining life