Are hurricanes and tornadoes, just to name a few extreme events, unique to our planet? And if so – why? Would similar kinds of weather events occur on other planets? Why do we have these events on our planet? What is it about the Earth that makes these possible and do they exist elsewhere? Or is each plant’s weather unique? I started our making a table that is a listing of just how varied the atmospheres of planets are and just how special Earth’s weather is; but a table misses the point. So, a description seems better.
The Ancient Greeks preached “Meden Agan”, and the golden mean. And in all my research I inevitable seek mathematical optimizations of competing multivariate solutions. But every time I contemplate this topic, I am drawn to the children’s story about Goldilocks and the Three Bears. In this children’s lesson, Goldilocks seeks the best between extreme choices. So it is with our planet’s composition.
The planets in order of their distance from the Sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and sometimes Pluto. Lets examine our solar system and the weather of each planet and the kind of storms they might have.
· Temperature – You might expect that the further away from the sun the colder the plant would be. And indeed that is the case. The average temperature in degrees Fahrenheit in parentheses for each planet is as follows: Mercury (333 F), Venus (867 F), Earth (56 F), Mars (-84 F), Jupiter (-166 F), Saturn (-230 F), Uranus (-320 F), Neptune ( - 330 F) and Pluto (-375 F)
· Surface Pressure – Surface pressure is the atomic mass of all the gass molecules above a point at the surfaces times the planet’s gravitational force. Here we are comparing each plant’s surface pressure to that of the Earth’s. Mercury (0), Venus (91), Earth (1), Mars (0.01 or equivalent to 40 miles above the earth’s surface ), Jupiter (unknown), Saturn (unknown), Uranus (unknown), Neptune (unknown) and Pluto (0)
· Gravity – Again expressed as a fraction of that of the earths: Mercury (0.38), Venus (2.8), Earth (1), Mars (0.38), Jupiter (2.4), Saturn (0.9), Uranus (0.9), Neptune (1.1) and Pluto (0.06)
· Diameter – Units are in miles: Mercury (3,032), Venus (75,521), Earth (7926), Mars (4,221), Jupiter (88,845), Saturn (74,897), Uranus (31,763), Neptune (31,775) and Pluto (1,485)
· Atmospheric gasses - Listed with the percentage of each gas in parentheses: ALL planets -- including the Earth -- have trace gasses, many of which are greenhouse gasses and very important.
o Mercury (trace),
o Venus CO2 (96 %), N2 (3.5 %), H2SO4 (clouds)
o Earth N2 (78 %), O2 (21 %)
o Mars (0.38), CO2 (95 %), N2 (3%)
o Jupiter NH3 , H2 O , CH4 and many trace gasses
o Saturn H (75%) and He (25%)
o Uranus H (75%) and He (25%)
o Neptune H (80%) and He (19%)
o Pluto (trace)
It is interesting that the four inner planets have a solid surface of similar composition, and the outer five are much larger and are all atmosphere with little or no solid core. The solid part of the inner planets is very similar to the earth. The giant gas planets (Jupiter, Saturn, Uranus and Neptune) are mainly liquid and gas, lacking a solid surface and mainly hydrogen and helium.
If Jupiter were 75 times bigger it would become a star. Still it looses about 2 cm of size each year due to outgoing radiation. When Jupiter was first formed, it was twice its presence size. The temperature of the planet and the force of gravity of a planet largely determine what gasses will comprise its atmosphere. It takes a large gravitational field to hold light gasses such as helium and hydrogen. Planets with weaker gravitational fields can hold only CO2 and other heavy gasses. The value of gravity is determined by the size of the planet and its composition. The inner planets (and some moons) have solid ground and their history resembles that of the earth with volcanoes and even water over a least a portion of their history.
Winds in some of the planets exceed 2,200 miles per hour. That would be equivalent to at Category 220 hurricane. Only the earth has much Oxygen and Nitrogen. The wind pattern in each planet’s atmosphere is largely governed by the speed of rotation, depth of the atmosphere, and the temperature at their equator vs the poles. I remember my first scientific publication while I was a first year graduate student. I collaborated with some scientists and Peter Stone from Harvard and we wrote a paper on the wind structure of Jupiter and Saturn as the result of symmetric baroclinic instabilities.
Next we will look at what determines what kind of weather planets have and if any have weather we would be familiar with. And what gives us the kinds of storms we have. From there we will go to what effects climate change will have.