Why Mercury Isn't The Solar System's Hottest Planet (Synopsis)

“There is no question that climate change is happening; the only arguable point is what part humans are playing in it.” –David Attenborough

If the Earth didn't have any global warming at all, our planet's mean temperature would be 255 K, or about -1º Fahrenheit: the mean temperature of the Antarctic continent. As it stands instead, our planet is much warmer than that, owing to the warming, insulating effects of the atmosphere, which is largely transparent to (incoming) visible light, but traps a fair amount of the (outgoing) infrared radiation.

Natural color image of Venus from Mariner 10 data. Image credit: © 2005 Mattias Malmer, from NASA/JPL data. Natural color image of Venus from Mariner 10 data. Image credit: © 2005 Mattias Malmer, from NASA/JPL data.

This effect is even more spectacular on our inner, sister planet, Venus. While Venus might be more reflective and twice as far from the Sun as Mercury, its greenhouse gases and insulating cloud layers are so effective that it's actually the hottest planet in the Solar System, outstripping Mercury day or night.

Transits of Venus (top) and Mercury (bottom) across the edge of the Sun. Note how Venus’ atmosphere diffracts sunlight around it, while Mercury’s lack of atmosphere shows no such effects. Images credit: NASA / SDO / HMI / Stanford Univ., Jesper Schou (top); NASA’s TRACE Satellite (bottom). Transits of Venus (top) and Mercury (bottom) across the edge of the Sun. Note how Venus’ atmosphere diffracts sunlight around it, while Mercury’s lack of atmosphere shows no such effects. Images credit: NASA / SDO / HMI / Stanford Univ., Jesper Schou (top); NASA’s TRACE Satellite (bottom).

Go get the whole story on the physics of why and how this is so over on Forbes!

More like this

"There is no question that climate change is happening; the only arguable point is what part humans are playing in it." -David Attenborough It's been a long time since I've written anything on this blog about global warming, climate change, or most Earth-based environmental topics in general. After…
"To consider the Earth as the only populated world in infinite space is as absurd as to assert that in an entire field sown with millet, only one grain will grow." -Metrodorus of Chios Later tonight, the European Southern Observatory is expected to make an announcement, and the smart money is on…
"In the far, far future, essentially all matter will have returned to energy. But because of the enormous expansion of space, this energy will be spread so thinly that it will hardly ever convert back to even the lightest particles of matter. Instead, a faint mist of light will fall for eternity…
Yesterday the MESSENGER spacecraft circled behind Mercury one last time, where no one on Earth could see it, and slammed into the surface of the intemperate planet at an estimated 8750 miles per hour. It was the second probe to visit Mercury—Mariner 10 completed three fly-bys of the planet in 1974…