Artist’s conception of sulfuric acid rain on Venus.
Bringing an umbrella in case of rain may have a different meaning depending upon the planet you’re on. Our umbrellas protect us from the rain showers here on Earth, but wouldn’t hold up very well if caught in a downpour of sulfuric acid rain on the planet Venus. Atmospheres surrounding different planets produce a wide variety of different weather patterns and atmospheric conditions, most of which are very hostile to human life. On Earth, atmospheric or air pressure is the force exerted on the Earth’s surface by the weight of the air above the surface. This is an important factor in determining weather patterns and especially when it rains. Our atmosphere contains water vapor and when the atmosphere pressure is low, clouds usually form and turn the water vapor into liquid water we call rain. On Venus however, the atmosphere contains opaque clouds made of sulfuric acid, so when it rains there it’s acid rain.
Further out in the solar system, the eighth and last planet in the solar system, Neptune has an atmosphere dominated by ices – methane and ammonia. But even with a chill in the air, Neptune still manages to host some of the most extreme and violent weather in the solar system. But most amazingly is that as a result of Neptune’s high temperatures and pressure, its methane gas can be turned into diamond. If liquid methane is squeezed to several hundred thousand times under extreme heat, diamond is produced and that’s what the weather conditions on Neptune are like. So if diamonds appear in Neptune’s atmosphere, they fall like raindrops or hailstones toward the center of the planet.
Colorized image captured by Cassini of methane lakes on Titan.
Other than Earth, the only known world to have liquid lakes is the planet Saturn’s largest moon Titan, the second largest moon in the solar system. Titan’s cloudy atmosphere is believed to be made of liquid methane, but the droplets of liquid methane in the rain clouds are 1,000 times larger than the rain drops here on Earth. NASA’s Cassini spacecraft still orbiting the Saturnian system has detected liquid methane lakes and rivers on Titan.
Artist’s conception of HD 189733b the exoplanet where it rains glass.
Atmospheres and weather conditions are not just confined to worlds of our solar system. Numerous planets orbiting other stars have been discovered and many of these are known to have atmospheres. Called exoplanets, these worlds range in sizes and distances from their parent sun. One such exoplanet, the size of Jupiter, is named HD 189733b and orbits a star 63 light years from us. Telescopic studies of this planet’s atmosphere imply that it contains significant amounts of water vapor and silicate particles resulting in a beep blue colored atmosphere. Because of this atmospheric mixture, when it rains on HD 189733b it comes down as glass particles. My favorite exoplanet with bizarre-like weather conditions is a far off world known as OGLE-TR-56b, another Jupiter sized planet. Intriguingly, the temperature of OGLE-TR-56b’s upper atmosphere is theoretically just right to form clouds, not of water vapor, but of iron atoms. Although unconfirmed, OGLE-TR-56b should experience exotic iron drops, thanks to strong heating from its nearby star.