So accustomed are we to the sunshine, rain, fog and snow of our home planet that we find it next to impossible to imagine a different atmosphere and other forms of precipitation.

To be sure, Dr. Seuss came up with a green gluey substance called oobleck that fell from the skies and gummed up the Kingdom of Didd, but it had to be conjured up by wizards and was clearly a thing of magic.

According to models by scientists at Washington University in St. Louis, COROT-7b's atmosphere is made up of the ingredients of rocks and when "a front moves in," pebbles condense out of the air and rain into lakes of molten lava below.

The work, by Laura Schaefer, research assistant in the Planetary Chemistry Laboratory, and Bruce Fegley Jr., Ph.D., professor of earth and planetary sciences in Arts & Sciences, appears in the Oct. 1 issue of The Astrophysical Journal.

Astronomers have found nearly 400 extra-solar planets, or exoplanets, in the past 20 years. But because of the limitations of the indirect means by which they are discovered, most are Hot Jupiters, chubby gas giants orbiting close to their parent stars. (More than 1,300 Earths could be packed inside Jupiter, which has 300 times the mass of Earth.)

COROT-7b, on the other hand, is less than twice the size of Earth and only five times its mass.

It was the first planet found orbiting the star COROT-7, an orange dwarf in the constellation Monoceros, or the Unicorn. (This priority is designated by the letter b.)

"The exoplanet COROT-7b is close enough to its star that its "day-face" is hot enough to melt rock. Theoretical models suggest the planet has an atmosphere of the components of rock in gaseous form and lava or boiling oceans on its surface. (Credit: Image by ESO/L. Calcada)"

Source: Washington University