Are There Many Potentially Habitable Planets? -Harvard Origins-of-Life Initiative Says "Yes"

"Super-Earths would be more geologically active than our planet, experiencing more vigorous plate tectonics due to thinner plates under more stress. Earth itself was found to be a borderline case, not surprisingly since the slightly smaller planet Venus is tectonically inactive."  

Harvard's Center for Astronomy

Our planet is changing before our eyes, and as a result, many species are living on the edge. New research by astronomers at the Harvard-Smithsonian Center for Astrophysics shows that if Earth had been slightly smaller and less massive, it would not have plate tectonics - the forces that move continents and build mountains. And without plate tectonics, life might never have gained a foothold.
"Plate tectonics are essential to life as we know it," said Diana Valencia of Harvard University. "Our calculations show that bigger is better when it comes to the habitability of rocky planets."

Plate tectonics -the movement of huge chunks, or plates, of a planet's surface- are crucial to a planet's habitability because they enable complex chemistry and recycle substances like carbon dioxide, which acts as a thermostat and keeps Earth balmy. Carbon dioxide that was locked into rocks is released when those rocks melt, returning to the atmosphere from volcanoes and oceanic ridges.

"Recycling is important even on a planetary scale," Valencia explained.

Valencia and her colleagues, Richard O'Connell and Dimitar Sasselov (Harvard University), examined the extremes to determine whether plate tectonics would be more or less likely on different-sized rocky worlds. In particular, they studied so-called "super-Earths"-planets more than twice the size of Earth and up to 10 times as massive.

"It might not be a coincidence that Earth is the largest rocky planet in our solar system, and also the only one with life," said Valencia.

Exoplanet searches have turned up five super-Earths already, although none have life-friendly temperatures. If super-Earths are as common as observations suggest, then it is inevitable that some will enjoy Earth-like orbits, making them excellent havens for life.

"There are not only more potentially habitable planets, but MANY more," stated Sasselov, who is director of the Harvard Origins of Life Initiative.

In fact, a super-Earth could prove to be have volcanic "rings of fire" that could span the globe while the equivalent of Yellowstone Park would bubble with hot springs and burst with hundreds of geysers. An Earth-like atmosphere would be possible, while the surface gravity would be up to three times that of Earth on the biggest super-Earths.

"If a human were to visit a super-Earth, they might experience a bit more back pain, but it would be worth it to visit such a great tourist spot," Sasselov suggested with a laugh.

He added that although a super-Earth would be twice the size of our home planet, it would have similar geography. Rapid plate tectonics would provide less time for mountains and ocean trenches to form before the surface was recycled, yielding mountains no taller and trenches no deeper than those on Earth. Even the weather might be comparable for a world in an Earth-like orbit.

"The landscape would be familiar. A super-Earth would feel very much like home," said Sasselov.

Posted by Casey Kazan. Adapted from a Harvard Center for Astrononmy release.

http://cfa-www.harvard.edu/press/2008/pr200802.html

Comments

[Yordan Yanakiev]

Well
i have a little calculation that I call :
"Worst case scenario"
( it's "worst case", because it's calculated at lower possibilites )
so here us the expression :

Out there have about 1 000 000 000 galaxies
each galaxy have about 1 000 000 000 stars
around each star orbit at least 3 planets

there is about ( 1 of each 10000 ) 0.01% possibilities to have a planet with Earth size

There is about 0.01% possibilities to have a water on it, and it's liquid

there is about 0.01% chance to develop life
( because of law "life is developed at each place offer the components to be developed" )

so - the final result is :

There have about 3 000 000 000 000 000 000 planets
at least 30 000 000 000 000 000 with Earth size
at least 300 000 000 000 000 with liquid water on it
at least 3 000 000 000 000 with developed life on it

so - say WELCOME to 3000 billions life forms :)

anyway - this is the worst case ...
actually - if we put 15 planets ( usually there is much larger solar systems out there )
and if we check the much larger possibilities of liquid water ( to say 10 % - which is much normal ) ...
well ... i ley your imagination work around :D

[maudyfish]

I hope they are proven wrong!! Because the normal assumptions scientist are making because of the data they have, means nothing when there is a universe so big and with so much diversity. Example: Who would have believed that a set of binary stars could orbit another set! Who would have believed that stars could be created so closely to black holes! Who ever thought there were plate tectonics on Earth!!

[jer35mx]

This is a minus in the general formulae to the habitable planets.

[claudio]

I rate the article at 5.

They have centered the main issue of the tectonic plates being an 'indispensible configuration for life to evolve'.

I am bit surprised about the Venus NOT having tectonic plates.....Venus has a large Volcano....how long they have measured the surface activity related to tectonic plate on Venus ?????
On Earth it is not every day you see tectonic plates movements (and quakes).....may that be 'inference' of the writer ????

Or may be that they with radars do not see the typical ocean ridges of the tectonic plates (radars are the only way to observe the Venus surface).

Well it sound more inference that objective 'long term tests of the planet surface' that in fact we do not have...about Venus.......but you never know...nowadays.

Many other factors are deemed also important for life to evolve (aside from the nice but a bit unsoundy scientists tantalizing about life forms on Titan).

Temperature and proper radiation spectrum of the star...Are both essential ...

So it is also essential that the planet itself is rich of Oxigen ...somehow...(CO2 is plenty of oxigen by the way)...

Water is deemed to be a main and crucial factor for life forms of various kind to evolve.

ATM is also important in the water-ATM echo system..

No ATM and only water (e.g. Europa) we might find out fishes and similar ocean stuff....if any...also given as granted the 'Europa ridges'.

There may be many other factors....becouse with a rough environment typical of tectonic plates...life forms have disappeared and re-born quite few times on this miniplanet.....

OK not all the planets hosting life have to be a xerocopy of Earth....I agree....BUT still there are additional factors are NOT only the tectonic plates...and the typical ridges that we have seen at Enceladus.

I like the count done by Yordan...it is a bit out of the usual Drake equation....but any equation could work....
However Yordan should recall the fact that many of the planets (galaxies) counted in his equation...are millions and billions of light years away...that means they now may not even exist anylonger...

We should never forget that more distant we look ..then we look at a more remote past...so remote that possible planet that we see now may have disappeared.....meanwhile.

The article is still top quality...well re-assembled by Casey as usual.

Regards