Weather Whys; Planet Mercury

This is weather wise. The tiny planet of Mercury is the second hottest of all the planets in the solar system. Only Venus with its runaway greenhouse effect gets hotter. Scientists believe temperatures at Mercury's equator can top 800 degrees Fahrenheit, and considering that at its closest point, Mercury is a little over a third as far from the sun as planet Earth. That type of temperature isn't surprising. Of course, 800 degrees Fahrenheit is a little too hot for liquid water to exist. In fact, it's too hot for any substance to exist in liquid form. So for years, scientists thought that any liquid that would have existed would have already boiled away, creating the vestiges of a very thin atmosphere around the planet. Solid substances like ice weren't thought to have a chance of existence on Mercury. New data shows that amazingly, Mercury may have ice caps at its poles. In fact, scientists now believe the temperature at Mercury's poles may be well below minus 200 degrees Fahrenheit.

Unlike Earth, Mercury isn't inclined on its axis at all, so the planet's polar regions receive only indirect sunlight all year round, sort of like a perpetual twilight. And even when you're a mere 30 million miles from the sun, you can't heat up that way. Considering that all the weather systems and storms on Earth result from the differences in the heating of the planet's surface, think what would happen if Mercury had an appreciable atmosphere. After all, a typical temperature difference between Earth's equator and its north pole might be on the order of 150 degrees. So if you think we have some fierce storms here, imagine what kind of weather would result from a 1,000 degree temperature difference. We'd like to know what you think of WeatherWise. Please write us at WeatherWise, KGOU Radio, the University of Oklahoma, Norman, Oklahoma, 73019-025-0. So WeatherWise, I'm Drew Barlow.