Space: Who Knew, #10

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Planet Mercury

This is what Mercury looks like from 17,000 miles away. Nasa's "Messenger" space craft (MErcury Surface, Space ENvironment, GEochemistry, and Ranging mission- website here) made its second fly-by of the planet earlier this morning, photographing a large area of the planet previously dark to us. It is the first spacecraft to actually orbit the smallest planet in our solar system.

Mercury closely resembles our moon, it is heavily cratered and has a diameter of only 3030 miles. That ranks it smaller than some moons in our solar system, like Saturn's Titan and Jupiter's Ganymede. Unlike our moon, Mercury has its own magnetic field (about 1% as strong as Earth's). This is due to its iron core, which makes Mercury extremely dense.

Lets see what else we can dig up on Wikipedia (article here).

The mean surface temperature of Mercury is 442.5 K,^[3] but it ranges from 100 K to 700 K,^[40] due to the absence of an atmosphere.

So that would be 336 degrees Fahrenheit, ranging from -279 to 800 degrees Fahrenheit. Wow.

On the dark side of the planet, temperatures average 110 K.^[41] The intensity of sunlight on Mercury’s surface ranges between 4.59 and 10.61 times the solar constant (1370Wm⁻²).^[42]

Despite the generally extremely high temperature of its surface, observations strongly suggest that ice exists on Mercury. The floors of some deep craters near the poles are never exposed to direct sunlight, and temperatures there remain far lower than the global average. Water ice strongly reflects radar, and observations by the 70m Goldstone telescope and the VLA in the early 1990s revealed that there are patches of very high radar reflection near the poles.^[43] While ice is not the only possible cause of these reflective regions, astronomers believe it is the most likely.^[44]

The icy regions are believed to be covered to a depth of only a few meters, and contain about 10¹⁴–10¹⁵ kg of ice.^[45] By comparison, the Antarctic ice sheet on Earth has a mass of about 4×10¹⁸ kg, and Mars’ south polar cap contains about 10¹⁶ kg of water.^[45] The origin of the ice on Mercury is not yet known, but the two most likely sources are from outgassing of water from the planet’s interior or deposition by impacts of comets.^[45]

Hmmm. Ice might exist on Mercury?

Who knew???