Planetary Meteorology
This lecture discusses the atmospheres of the planets in the Solar System other than the Earth.
The Solar System, including the sun and the planets, formed at approximately the same time some 5 billion years ago. The sun was formed from a conglomeration of swirling hot gases. The remaining gases left over coalesced and condensed to form the planets.
The planets in the Solar System are (from closest to the sun to furthest):
For information on how far the planets are from the sun and how long their orbital periods are, visit the following web site address: http://www.uaeu.ac.ae/resources/SolarSystem/distance.html
7 of the 9 planets in the Solar System have atmospheres. The atmosphere of a particular planet is determined largely by the size of the planet. The more massive a planet is, the more easily it will be able to retain an atmosphere due to the stronger graviatational forces. For instance, the two smallest planets in the Solar System, Mercury and Pluto, do not have atmospheres.
Other factors that influence the atmosphere of a planet is its internal geology. The Earth's atmosphere was formed in part due to the gases that were released during Earth's period of heavy volcanic activity.
Venus
Venus' atmosphere is very hostile and intimidating. The pressure on Venus is some 60 times that of Earth's! An aluminum can would be crushed if it were allowed to stand freely on Venus' surface. The atmosphere of Venus is composed primarily of Carbon diOxide and Sulfuric Acid. Both Carbon DiOxide and Sulfuric Acid are Greenhouse Gases which insolate the planet and prevent heat from escaping back into space. As a result, the atmosphere of Venus continues to grow hotter and hotter. Average temperatures on Venus average between 800 and 1100 degrees F.
The United States has tried, however unsuccessfully, to land unmanned space probes on the surface of Venus. In all instances, the instrumentation failed in the hostile Venetian environment.
The Russians however successfully landed a Venera spacecraft on Venus.
Venus can be seen in the early evening or early morning sky just above the horizon from where the sun rises (AM) or sets (PM). Venus is often referred to as the Morning Star or the Evening Star.
Mars
Mars, often known as the Red Planet, has a very thin atmosphere. Its pressure is less than 1 % that of Earth's. The primary constituent of the Martian atmosphere is Carbon diOxide. There is believed to be traces of water vapor in the Martian atmosphere.
Mars has 2 Moons, Phobos and Deimos. Neither of the two Martian Moons have atmospheres.
There have been several unmanned space probes to the Red Planet. In the mid 1970s, the Viking series of spacecrafts flew to Mars and investigated the Martian soil and the Martian atmosphere.
In December 1996, the US launched the Pathfinder Space Mission. On July 4th of this year, it reached Mars and began sending back photographs instantaneously. Much has been learned about the Martian atmosphere as a result of the Pathfinder Space Mission.
Mars is often visible in the nighttime sky as an unmistakable red object.
Jupiter
Jupiter is the first of the Gas Giants from the sun. Jupiter is some 343,000 times the size of the Earth. It is composed primarily of gas. Jupiter's gases include Methane, Ammonia, Sulfuric Acid, and Carbon DiOxide.
One of the more interesting features of the planet Jupiter is the Giant Red Spot on the planet. The red spot is actually an area of intense storminess that travels around the planet every 18 hours or so.
Winds on Jupiter blow at an average of about 400 mph.
Some scientists speculate that Jupiter may have a solid core. In the nighttime sky, Jupiter often looks yellowish or even orange. At times, Jupiter is very bright and approaches the brightness of Venus.
Jupiter has many moons (upward of 20) but the four major moons are the Galilean Moons - Io, Europa, Gandymede, and Callisto. Each of these moons have unique characteristics and Europa and Io even have atmospheres. Gandymede has active volcanos.
Sautrn
Saturn is known most commonly for its beautiful rings that encircle the planet. The atmosphere of Saturn is comparable to Jupiter's. Swirling clouds of methane, ammonia, and sulfuric acid encircle the planet. Voyager 2 passed by Saturn in the 1980s and returned some spectacular photography.
The rings of Saturn are actually individual pieces of rock and debris. Some speculate that the rings formed when a comet collided with a pre-existing moon of Saturn.
Saturn has 9 moons. In the nighttime sky, Saturn looks like a bright silvery-white star.
Uranus and Neptune
These two planets are very similar in size, color, and composition. They are distant planets. On rare dark nights, Uranus can be seen in the nighttime sky with the naked eye. It looks like a dim green star. The atmospheres of Uranus and Neptune are composed largely of ammonia gas. The planets have a bluish-green appearance.
Uranus has 5 moons and Neptune has 2. The largest moon in the Solar System belongs to Neptune and is called Triton.
Learn more about the planets and unmanned space flights to the planets by visiting the NASA Web Site.