Why some moons are larger than Mercury but less massive

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Some moons are bigger than Mercury

Some of the Solar System’s largest moons are physically larger than Mercury but less massive. Mercury is unusually dense, while these moons contain more low-density material, including ice.

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A lunar crater can be colder than Pluto

26 K (−247 °C)

A spacecraft measured 26 K (−247 °C) near the winter solstice in Hermite, a permanently shadowed crater near the Moon’s north pole. It was the lowest temperature the spacecraft had measured anywhere in the Solar System.

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Rising oxygen may have helped trigger ancient ice ages

When oxygen began rising in Earth's atmosphere, it likely destroyed some methane, a powerful heat-trapping gas. This weakened the greenhouse effect and may have helped trigger the Huronian ice ages.

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