Extraterrestrial Memes Finding Nommo Oceans May Be Common On Rocky Alien Planets
MARCH 26, 2013 - SPACE - Every rocky planet likely develops a liquid-water ocean shortly after forming, suggesting that potentially habitable alien worlds may be common throughout the universe, a prominent scientist says.

The building blocks of rocky planets contain more than enough water to seed oceans, and computer models and Earth's own history suggest such seas should slosh around soon after these worlds' surfaces have cooled down and solidified, said Lindy Elkins-Tanton of the Carnegie Institution for Science in Washington, D.C.

This artist's conception shows the inner four planets of the Gliese 581 system and their host star. The large planet in the foreground is Gliese 581g, which is in the middle of the star's habitable zone and is only two to three times as massive as Earth. Some researchers aren't convinced Gliese 581g exists, however.

CREDIT: Lynette Cook

"Habitability is going to be much more common than we had previously thought," Elkins-Tanton said today (March 18) during a talk at the 44th Lunar and Planetary Science Conference in The Woodlands, Texas.

Analysis of ancient Earth rocks shows that our own planet hosted an ocean of liquid water at least 4.4 billion years ago, Elkins-Tanton said - just 160 million years or so after our solar system's birth. This water came primarily from the planetesimals that glommed together to form Earth long ago rather than from comet impacts, as some researchers had previously believed, she added.

WATCH: Possibly habitable Super-Earths.

That's an exciting prospect for astrobiologists, as life on Earth is found nearly anywhere liquid water exists.

HOLDING ON TO THE WATER


Of course, forming an ocean and holding onto it are two different matters. After all, Earth's solar system hosts rocky planets - Mercury, Venus and Mars - whose surface oceans have long since disappeared, if they ever existed at all.

Indeed, how some rocky worlds manage to retain their water is an area ripe for future research, Elkins-Tanton said, specifically citing the case of Venus, Earth's hellishly hot "sister planet" that veered down a very different road after its formation.

It may be tempting to ascribe the apparent dessication of rocky worlds like Venus to the giant impacts that pummeled them in our solar system's early days. But Earth held onto much of its water despite a massive collision with a Mars-size body (which is thought to have led to the formation of the moon), and data from NASA's Messenger spacecraft show that Mercury still harbors many volatile compounds, Elkins-Tanton said.

"Now if there would be a poster child for the body that should be depleted by giant impacts, that would be Mercury," Elkins-Tanton said. "Giant impacts do not dry bodies." - SPACE.