Astro Bob blog: Love song for a temperate planetBreathe in the good air of spring on breezy planet Earth
By: Bob King, Duluth News Tribune
Love song for a temperate planet
The view looking south at the beginning of dawn Saturday morning. The bright moon will be near Antares, the heart of the Scorpion. The conjunction is visible with the naked eye and might appear even prettier in binoculars. Created with SkyMap software by Chris Marriott
Tomorrow morning a wee bit on the early side the waning gibbous moon will pass a little more than one degree above the bright star Antares in Scorpius the Scorpion. This close lineup of the moon and another star or planet (or of two planets) is called a conjunction. Although very early for some, those who do venture out share the sky with the company of birds and perhaps even frogs. Hearing robins, song sparrows and phoebes begin their day makes for a great way to start mine.
Frogs have returned to the neighborhood although I suppose they never left. I heard wood frogs two nights ago and my first spring peeper last night. Spring is coming along nicely with new characters on the scene and air that's easier on the lungs.
Air's a good thing -- it's responsible for keeping the planet warm and habitable, provides essential oxygen to our cells and transmits sound waves so we can hear frogs or that car coming up the road.
An artist's view of Venus' surface and perpetual overcast skies. Light from the sun is filtered by clouds and sulfuric acid drops casting a yellow glow over the landscape. The air pressure is the same as what you would feel if you were a kilometer (0.6 miles) beneath the surface of an ocean here on Earth. Credit: ESA
The moon and Mercury are essentially vacuums with not a sound to be heard except for your beating heart; the other planets have air of one form or another but it's too poisonous or suffocating to breathe. Venus' air pressure is 90 times that of Earth and the air consists of 97% carbon dioxide laced with fine droplets of sulfuric acid. The air on Mars is also primarily CO2 but with a pressure at the other extreme -- just under 1% that of Earth's. Want to get a feel Martian air pressure? Just open a window on a high-flying aircraft at an altitude of 22 miles.
Hydrogen (mostly) and helium compose the atmospheres of Jupiter and Saturn along with small amounts of water, ammonia, sulfur and phosphorus compounds. These planets' primary ingredients should sound familiar -- they're the same ones of which the sun is made. Jupiter has often been called a "failed star", a very judgemental way of saying that had it been a larger ball of hydrogen and helium it would have initiated nuclear fusion in its core and burned to become a star. The king of the planets is a long way from stardom. To do so it would have to be 80 times more massive. I'm happy with Jupiter as it is. So maybe you can't breath its air, and sure you have to be careful not to not light a match with all that hydrogen around, but the planet is one of the coolest to view through a telescope. The cloud belts and changing weather patterns offer up nonstop surprises.
Titan's atmosphere is much thicker than Mars'. This photo shows layers of haze in Titan's atmosphere. Sunlight breaks molecules of methane in the atmosphere apart and the byproducts combine to form other compounds like ethane and acetylene. These are familiar on Earth as fuels and chemicals used in industry. Credit: NASA
The atmospheres of Uranus and Neptune are similar to Jupiter and Saturn and consist of 80-83% hydrogen and 15-19% helium. Most of the remaining gas is methane which tints both planets blue. Titan, Saturn's largest moon, not only has a substantial atmosphere but its composition is more like the Earth's than any other body in the solar system. Titanian air pressure is 1.6 times that of our planet (like being about 20 feet underwater) and composed of about 90% nitrogen and 10% methane and other carbon-rich gases. Earth's air is composed of 78% nitrogen, 21% oxygen with very small amounts of carbon dioxide, water vapor and other gases. Yes, we do share similar amounts of nitrogen but with no oxygen and temperatures there of 290 below zero you wouldn't exactly want to remove your space helmet and breathe the country air.
To complete our breezy survey of solar system I should mention that three additional moons have trace amounts of an atmosphere: Jupiter's Europa (oxygen) and Io (sulfur dioxide) and Neptune's Triton (nitrogen and methane).
As spring takes the edge off the previous season, let's breathe in deeply to enjoy the only place in the solar system where we can be one with the air.