Exoplanet Weather Forecast: Cloudy. Outlook: Cloudy

As we discover more exoplanets, many are more alien than we can possibly imagine. But occasionally, there's an air of familiarity about a few of the discoveries. In new research showcased in two papers published in the journal Nature, the atmospheres of two exoplanets are described. Specifically, their cloud cover was observed, revealing that even exotic new worlds have grey days.

PHOTOS: Exquisite Exoplanetary Art

The two research papers focus on two exoplanets in our galactic neighborhood. One, a super-Earth, is called GJ 1214b and located ‘only' 42 light-years away. The second world, a Neptune-sized exoplanet, is called GJ 436b and located 33 light-years away.

GJ 1214b is the smallest planet so far to have its atmosphere probed, but don't get excited for cloud-filled alien vistas over a habitable landscape. This world, which is nearly three times the size (and 6.5 times the mass) of Earth, orbits its red dwarf star every 38 hours. Although red dwarf stars generate less energy than stars like our sun, the exoplanet's racetrack orbit is so compact that its surface temperature is very toasty, ensuring a dense, hot atmosphere.

Previous observations in 2010 detected no atmospheric signature on GJ 1214b, even though astronomers know that it does possess one. As the world orbited in front of its star from our perspective (an event known as a "transit"), starlight appeared to not pass through any atmosphere as far as researchers could tell. That meant there were two possible conclusions: 1) GJ 1214b has an atmosphere thick with clouds that block the starlight from passing through the atmosphere or, 2) something more exotic is going on - possibly a thin, dense layer of heavy molecules (such as water) encapsulates the world; a layer that is too thin to be detected by instrumentation.

ANALYSIS: Exoplanet Weather Forecast: Hot and Nasty

But now, using the Hubble Space Telescope, researchers have been able to discern what's really going on: the exoplanet's atmosphere is thick with clouds, blocking the starlight from view.

After studying 15 transits of GJ 1214b, infrared Hubble observations should have detected the spectroscopic signature of atmospheric water molecules if water was present, but it did not. Although water could still be present in the atmosphere, "there also have to be clouds" enshrouding the upper atmosphere, said lead researcher Laura Kreidberg, of the University of Chicago in Illinois.

As noted by Nature News, these clouds would be unlike anything we experience on Earth. Due to the hot, dense nature of GJ 1214b's atmosphere, the clouds are likely rich with zinc sulphide or potassium chloride. These chemicals would be able to condense and form microscopic droplets, thus forming the cloud cover.

"It's the first time that we've been able to characterize the atmosphere of an exoplanet smaller than Neptune," said Kreidberg.

ANALYSIS: Exoplanet Forecast: Cloudy, With Chance of Maelstrom

A similar technique, using Hubble data, was carried out in the GJ 436b study. Once again, spectroscopic data reveal no chemical signature of an atmosphere, an outcome that is completely unexpected from observations of a Neptune-class planet. The most likely explanation is that a thick layer of high-altitude cloud is blanketing the exoplanet, blocking the starlight from passing through the atmosphere, preventing a spectroscopic measurement from being made.

"We always knew the clouds must be there for some planets, but now we have a wave of results telling us that clouds are actually very common," said planetary astronomer Heather Knutson, of the California Institute of Technology (Caltech) in Pasadena, Calif., and lead author of the GJ 436b study.

Artist’s impression of GJ 1214b, which astronomers say has an atmosphere thick with clouds. Credit: NASA, ESA & G.Bacon

Extreme Space Weather

Oct. 3, 2011 --

With hurricanes, floods, massive thunderstorms, heat waves and wildfires, we might be inclined to believe that the weather on Earth is sometimes less than hospitable to the life that inhabits it. But compared to other planets, stars and other bodies in the cosmos, the weather on Earth is downright mild. In this slide show, explore what conditions are like elsewhere in the universe. By the time you're done reading this slide show, you'll know exactly what to say the next time you hear someone whining about the weather: "Quit complaining. At least we don't live on HD 209458b."

The Sauna Planet "It's not the heat; it's the humidity" is a common expression on especially muggy days in the heat of the summer. But on exoplanet GJ 1214b, we guarantee you won't notice the difference. Located about 40 light-years from our planet, this super-Earth waterworld is believed to possess an atmosphere of dense steam. The exoplanet is between two and 10 times larger than Earth and located approximately 70 times closer to its parent star. Essentially, this planet is one giant sauna, turned up to temperatures in excess of 1,000 degrees Fahrenheit (537 degrees Celsius).

Mars Storms Hurricanes are the largest storms on Earth. With powerful wind gusts and heavy rains, the storms can take a devastating toll on millions at a time. But in terms of size, they can't compare to the dust storms that can roll across Mars and affect the entire planet. In fact, some storms are so large that amateur astronomers can occasionally view them using ground based telescopes. During dust storms, wind gusts can reach up to 300 miles per hour, far stronger than any storm ever recorded on Earth.

Supersonic Planet If you're a windsurfing enthusiast, HD189733b may be just the right place for you. That is, at least it would be if it weren't 60 light-years away and orbiting its parent star so closely. Classified as a hot Jupiter, this gas giant hosts wind speeds that exceed the speed of sound. And since, as Adam Showman of the University of Arizona Lunar and Planetary Laboratory explains, the speed of sound of HD189733b is 10 times faster than it is on Earth, that's a pretty significant accomplishment. To put a number on it, the winds can reach speeds of around 6,700 miles (10,870 kilometers) per hour. That should help to cool down any potential visitors, since the temperature on the surface of the planet facing the sun can reach 1,700 degrees Fahrenheit (926 degrees Celsius).

Tidally Locked World Located some 150 light-years from Earth, HD 209458b is a hot Jupiter with one major convenience: You never have to bother to set your watch. The planet is in a tidally locked orbit with its parent star, meaning one side is always facing the sun and the other side is stuck in perpetual night. Because of this disparity, the planet also has strong winds similar to those of HD189733b. However, wind speeds on this planet only reach 4,500 miles per hour, making it a better option for a thrill-seeking windsurfer who might still be holding out hope of keeping a hair or two in place.

Forget Jupiter The swirling storm at the center of Jupiter's Great Red Spot might get all the attention in our solar system. But that storm is a tiny tyke compared to the one on this brown drawf. Affectionately called "2MASS J21392676+0220226," this brown dwarf is located approximately 47 light-years away.

Solar Storms Unlike the weather mentioned in every other entry on this slide show, storms on the sun can have a significant impact on life on Earth. As storm activity increases in frequency as the sun approaches its solar maximum in its 11-year cycle, solar flares and coronal mass ejections can threaten the functionality of satellite systems, affecting computer, navigation and telecommunications networks on Earth, as well as potentially disrupt power grids. Unfortunately, an umbrella won't do us much good in the event of a massive solar storm as the sun blasts plasma particles at Earth at speeds of hundreds of miles per hour. But that doesn't mean there's reason to panic, either. (Not yet, anyway.)

Honorable Mention: Black Holes If you're chasing massive storms in space, nothing quite rivals the strength and intensity of the tidal forces created by a hungry black hole. When black holes tear into stars, they pull in gasses from that star at such high speeds as to create bright gamma-ray bursts that are detectable from Earth. Anything that comes near a black hole is stretched out, then ripped apart and smashed together again with other matter at velocities approaching the speed of light. If there's one storm you absolutely don't want to get caught in this year, it's one created by drifting too close to a black hole.

More stories by Talal Al-Khatib.