The Frostburg State Planetarium reopens today with free public programs at 4 p.m. and 7 p.m., each lasting about 45 minutes in Tawes 302 (just within the front lobby with a water fountain and restrooms further down the hall).

Our programs start with a quick review of current evening sky sights using our planetarium projector, where visitors can ask questions. Our main feature this month is “Our Glorious Atmosphere,” which will be repeated on all remaining Sundays in January.

Then following a brief intermission, any interested visitors can see an outstanding display of preserved mammals from five continents in the nearby Science Discovery Center. This is the collection of Dr. Joseph Cavallaro, a native of Westernport and a graduate of the University of Maryland Medical School.

Just as the planetarium, the tours of the Cavallaro Collection are free; there are no restrictions on photography of the animals, which include lions, leopards, baboons, antelopes, sheep, deer and bears. School classes can visit the Science Discovery Center during school hours without charge; call (301) 687-4120 to make arrangements.

When one considers the other planets’ atmospheres, the air above us is very special.

The innermost planet Mercury has an extremely thin atmosphere, gases blown out of the sun that can’t be held due to Mercury’s low surface gravity and high daytime temperatures.

The next planet from the sun is Venus, whose smothering atmosphere bottles up heat. During both day and night, Venus’ surface temperature is about 870 degrees F. The clouds of Venus are ten times higher than our clouds and full of sulfuric acid. When it tries to rain on Venus, the surface heat causes the acid drops to boil back up into the clouds!

The planet Mars has an atmosphere that has been slowly leaking into space over billions of years. With a density less than 1 percent of our air, Mars’ thin atmosphere lets the daytime heat escape each night; surface temperatures just before dawn are about -100 degrees F all over the planet.

What characteristics of our atmosphere make the Earth so ideal for life? Our neighbor worlds have atmospheres that are either too thin or too thick. The Earth’s atmosphere mixture traps enough of our surface heat to raise our temperature nearly 60 F. Otherwise, the average surface of the Earth would be about 0 F. The three main heat trapping gases in our atmosphere are: water vapor, carbon dioxide and methane (CH4).

Venus has thousands of times more carbon dioxide than Earth, turning her surface into an inferno. Earth’s main atmospheric gases are: nitrogen (nearly 80 percent), oxygen (nearly 20 percent), water vapor (typically about 1 percent) and argon (nearly 1 percent).

Where do these gases come from? The oxygen comes from photosynthesis, the process where plants take carbon dioxide, water and through the action of sunlight make carbohydrates and exhale oxygen. The water vapor is mainly from evaporation taking place in the ocean.

Argon (the gas used in standard light bulbs) is from radioactive potassium. Nitrogen comes from the breakdown of ammonia, NH3 where the hydrogen escapes into space, leaving nitrogen (N) behind. Most of these gases came either from volcanic eruptions (at any one time about a dozen volcanoes are now active) or comets impacting the Earth (frozen H2O and NH3).

The atmosphere has four layers, defined by how the temperature changes with height. The lowest level is the troposphere, where weather takes place and temperature drops with increasing height. About six miles high begins the stratosphere where the temperature climbs with increasing height. The stratosphere contains the ozone (O3) layer, that protects life on land and floating aquatic life from the sun’s ultraviolet rays.

Above 30 miles height is the mesosphere, where the temperature drops with increasing height. Higher than 50 miles height is the thermosphere where the temperature climbs with increasing height. Here the meteors flare and the northern lights glimmer. The thermosphere which extends to 120 miles altitude can be considered the last atmospheric layer.

My next columns will cover other aspects of the atmosphere, including why the weather changes, how the atmosphere has changed, an overview of the climate change discussion and what is likely to occur in coming decades.

The moon is now a crescent, appearing near the pinkish star Antares tomorrow in the 6:30 a.m. dawn.

In the evening twilight, the very bright planet Jupiter shines low in the west. As Jupiter disappears behind the trees, hills or houses, the yellow-orange planet Mars shines low in the east.

The bright star group Orion, with his three star belt is high in the Southern evening sky. Orion’s belt points down and left to Sirius, the night’s brightest star.

Bob Doyle invites readers’ comments or questions; email him at rdoyle@frostburg.edu .