Out There: Billions and Billions of Habitable Planets

[DazzaMc]

Out There: Billions and Billions of Habitable Planets

There are about ten thousand billion billion habitable planets in the observable universe, and some of these Earth-like worlds could be found by a mission set to launch early next month, a leading planet-formation theorist now speculates.

Alan Boss, astrophysicist at the Carnegie Institution in Washington, D.C., and author of "The Crowded Universe" (Basic Books), published this month, came up with that rough number by estimating there is about one habitable planet around every sun-like star in the galaxy, of which there are about 10 billion, and multiplying that by the number of galaxies in the universe (about 100 billion).

This result is inexact of course, so give or take a power of ten or so, Boss said, which is standard for these types of estimates in astronomy.

"Based on what we already know, the universe is going to turn out to be chock full of habitable planets (i.e. Earth-like worlds), and therefore life is likely to be widespread," said Boss, who discussed these estimates with a group of reporters last weekend in Chicago at the annual meeting of the American Association for the Advancement of Science.

The promise of 'super-Earths'

To date, precisely zero of these other Earths have been found. Technology simply has not allowed their discovery, presuming they exist. But astronomers are closing in. In the past nearly 15 years, more than 300 planets have been found around stars beyond the sun.

Three classes of planets have been found, for the most part — Jupiter-like gas giants, Neptune-like icy planets and hot "super-Earths." Such super-Earths, such as one reported by the Carnegie Institution's Paul Butler in 2004 around Gliese 436 and another reported the same year by Barbara McArthur of the University around 55 Cancri, have masses of about five to 10 times that of Earth and exist around one-third of all nearby stars like our sun, Boss figures. This estimate is based on the results of ongoing planet-search efforts using the gravitational tug of planets on stars to detect worlds, called the Doppler approach, he said.

Most of these super-Earths are too hot to support life, but Boss thinks there are warm super-Earths, with longer period orbits and more suitable for life. Examples are two warm or cool super-Earths reported in 2007 by Stephane Udry and his colleagues on the Geneva Observatory to be orbiting Gliese 581.

And, some of the icy planets might turn out to be rocky planets similar in composition to Earth, only more massive, Boss said.

"We already know from folks who have been finding planets around other stars that most stars have planets," he said, adding that "simply from a theoretical ground of understanding how stars form, it's almost inevitable that they should end up having disks around them which should end up forming planets. So we expect them to be there from the point of view of theory as well."

Kepler will test it

Boss's claims will be tested by NASA's Kepler mission, a 1-meter-diameter space telescope set to launch March 5 from Cape Canaveral aboard a Delta 2 rocket. Among other tasks, Kepler is designed to count the number of Earth-sized and larger planets in the habitable zone around stars like the sun. Results should come in the next three or four years.

Kepler will detect planets using the "transit technique," which involves inferring the presence of a planet by detecting the dimming of star light caused by the passage of the orbiting planet in front of the star.

In the search for Earth-like planets, Kepler will be racing against the French-led CoRoT (Convection, Rotation and Planetary Transits) mission, a 27-centimeter-diameter space telescope launched in 2006. CoRoT already has found the smallest planet (COROT-Exo-7b) ever detected orbiting a sun-like star. Twice the size of Earth, the exoplanet's temperature is so high that it could be covered with lava or water vapor, CoRoT scientists said.

"We'd be astonished if Kepler and CoRoT did not find planets, because they are already finding them," Boss said. Kepler might find more planets than CoRoT because its telescope has a larger diameter (therefore it is more sensitive) and it will survey a larger patch of sky, he said.

"The fact that we can find [roughly Earth-sized planets] already implies that we are just seeing just the tip of the iceberg. There might be many more Earths out there waiting for us to find," Boss said.

And some of these could be found relatively close to Earth, he said.

"There are something like a few dozen solar-type stars within 30 light years of the sun," Boss said. "I would think a good number of those, perhaps half of them, will have Earth-like planets. So I think there are very good chances that we'll find some Earth-like planets within 10, 20, 30 light years of the sun."

Once the frequency of habitable-Earth-like planets in our neighborhood of the galaxy is known, scientists will be better able to design space telescopes capable of imaging those worlds and detecting evidence of the molecules necessary for life, such as water and oxygen, and possibly even those created by life, such as methane, Boss said.

What took you so long?

Physicist Enrico Fermi, who lived in the first half of the 20th century and is known for developing the first nuclear reactor, thought there was intelligent life beyond Earth, but famously wondered why we haven't heard from it yet (this question is called Fermi's Paradox), Boss writes in his book.

"The answer to that question ranges from practical to suicidal," Boss told reporters Saturday.

The suicidal version: "Maybe it means civilizations which are capable of sending us radio signals just don't last that long. ... Do we really think our civilization is going to last 1 billion years?"

The practical version: "There is a low probability of success [as with the SETI effort], but if you find something you have an immensely important finding."

Traveling to even the closest star orbited by a planet with habitable life could take us hundreds of thousands of years, he said.

Meanwhile, the impact of CoRoT and Kepler finding Earth-like planets around sun-like stars will be huge, Boss said.

"Once we find the first one we'll have made the point that they really are there," Boss said. "Just by finding the first one we'll able to immediately say, 'Well if we found one around a nearby star, just by multiplying the volume of the stars searched versus the ones that have not been searched, we can infer there must be billions and billions more of them just within our own galaxy.' So finding the first one will have enormous implications for how many there are in the entire galaxy as well as in the entire universe."


http://www.space.com/scienceastronomy/090219-explanets-life.html

[DazzaMc]

Plate Tectonics Could Be Essential for Alien Life

Plate tectonics is the process of continents on the Earth drifting and colliding, rock grinding and scraping, mountain ranges being formed, and earthquakes tearing land apart. It makes our world dynamic and ever-changing. But should it factor into our search for life elsewhere in the universe?

Tilman Spohn believes so. As director of the German Space Research Centre Institute of Planetary Research, and chairman of ESA's scientific advisory committee, he studies worlds beyond our Earth. When looking into the relationship between habitability and plate tectonics, some fascinating possibilities emerged.

Knowing where to look

It is thought that the best places to search for life in the universe are on planets situated in "habitable zones" around other stars. These are orbital paths where the temperature is suitable for liquid water; not so close to the star that it boils away, and not so far that it freezes. Spohn believes that this view may be outdated. He elaborates, "you could have habitats outside those, for instance in the oceans beneath ice covers on the Galilean satellites, like Europa. But not every icy satellite would be habitable. Take Ganymede, where the ocean is trapped between two layers of ice. You are missing a fresh supply of nutrition and energy."

So planets and moons that lie beyond habitable zones could host life, so long as the habitat, such as an ocean, is not isolated. It needs access to the key ingredients of life, including hydrogen, oxygen, nitrogen, phosphorous and sulphur. These elements support the basic chemistry of life as we know it, and the material, Spohn argues, must be regularly replenished. Nature's method of achieving this on the Earth appears to be plate tectonics.

Plate tectonics - essential for life?

It is an idea growing in popularity among planetary scientists. Says Spohn, "plate tectonics replenishes the nutrition that primitive life could live on. Imagine a top surface that is depleted of the nutrition needed for bacterial life. It needs to be replenished, and plate tectonics is a method of achieving this."

Spohn found that the further he delved into the issue, the more important plate tectonics seemed to be for life. For example, it is believed that life developed by moving from the ocean to the kind of strong and stable rock formations that are the result of tectonic action. Plate tectonics is also involved in the generation of a magnetic field by convection of Earth's partially molten core. This magnetic field protects life on Earth by deflecting the solar wind.  Not only would an unimpeded solar wind erode our planet's atmosphere, but it also carries highly energetic particles that could damage DNA.

Another factor is the recycling of carbon, which is needed to stabilize the temperature here on Earth. Spohn explains, "plate tectonics is known to recycle carbon that is washed out of the atmosphere and digested by bacteria in the soil into the interior of the planet from where it can be outcast through volcanic activity. Now, if you have a planet without plate tectonics, you may have parts of this cycle, but it is broken because you do not have the recycling link."

It has also been speculated that the lack of tectonic action on Venus contributed to its runaway greenhouse effect, which resulted in the immense temperatures it has today.

All this evidence adds up to paint a convincing picture of many lifeforms only surviving on worlds where plate tectonics are active. For astrobiologists, there is another interesting element to this story. Many within the planetary science community believe that to have plate tectonics, the near-surface rock must be weakened. The molecule most effective at doing this is H2O -- water. So worlds with plate tectonics are likely to have water as well, which means they feature two ingredients theoretically necessary for life.

Raising hopes

This presents an exciting option: searching for plate tectonics on distant worlds as a sign of life. Spohn agrees that this is a possibility, but remains level-headed. "It's an interesting idea, but is just speculation at the moment," he explains. "As a biosignature it would be very difficult to detect, especially with current technology".

The problem is how challenging it is to spot plate tectonics from orbit even on our own Earth. The jig-saw puzzle shape of continents along with the presence of mountain belts provides indirect evidence. Mid-oceanic ridges are more convincing, but these are covered with water and not visible from space. To see features on an extrasolar planet would require a probe in orbit, and this is far beyond our technological ability. Even if we were able to achieve this, the evidence would still be indirect. Currently there is no conclusive way of remotely determining tectonic action on a planet.

So perhaps using these markers as an indication of life on other worlds is a step too far, but as our technology becomes ever more complex it could become a possibility in the future. Imagine detecting an Earth-sized planet with an atmosphere, water, organic materials, and plate tectonics. It would unquestionably raise hopes for finding life in the universe.

http://www.space.com/scienceastronomy/090219-am-plate-tectonics-life.html

[DazzaMc]

What Finding Alien Life Could Mean for Earth

Imagine that tomorrow morning scientists tell the world they've found evidence for a colony of aliens living only 35 million miles from Earth.

Do you think your neighbors would wig out - stocking up on Ramen noodles, and secluding themselves and the family schnauzer in the basement? Or do you believe most folks would simply mutter "whatever," and go back to checking out new Facebook friends?

The question's not altogether fatuous, because this kind of discovery could happen soon, thanks to the efforts of astrobiologists - researchers who study the origin, nature and distribution of life. 

Although we still haven't found any biological activity elsewhere, it's hardly inconceivable that before your car gets its next oil change, robot spacecraft could discover a horde of microbes hidden beneath the Martian sands. Or maybe a few years down the road, some astrobiology experiment will stumble across alien pond scum floating in Titan's rime-frosted lakes, or pick up a radio signal beamed earthward from the star system Gliese 581.

The impact of such news would be significant and, at this point, largely unknown. So to get a better grip on how astrobiological discoveries would play out, the SETI Institute and the NASA Astrobiology Institute recently held a three-day workshop to bring together scientists, ethicists, historians, lawyers, anthropologists, and the media to consider the societal consequences of this type of research.

It's obvious that three days of conversation is thoroughly inadequate for gauging the cultural repercussions of astrobiology's wide range of research. So Margaret Race, the organizer of the event and a scientist at the SETI Institute, suggested that the forty-and-more participants simply devise a "roadmap" - a reconnaissance of the issues, if you will. What should we be studying in this field?  As the traveling salesmen in The Music Man insisted, "you've got to know the territory."

Well, let me tell you: the territory is immense, and encompasses such dramatic and controversial conundrums as protecting ourselves from errant asteroids (is it OK to deflect an incoming rock just enough to keep it from pulverizing your own country but let it wallop, say, western China?) and dealing with the possibility of synthetic life, cooked up in a lab (should there be controls on such research?)

I won't even try to survey the field. But I will offer an example that will keep your brain warm if you ponder it during your ride to work.  It's the scenario that began this short essay, and it will give you some flavor of the type of problems foreseen by the workshop participants.

It goes like this. As zealous followers of space research know, there's now good evidence for methane floating above the Martian landscape in several regions of the planet. Now there are only two straightforward explanations for this gas: (1) the methane is the consequence of geological activity, such as volcanism, or (2) it's produced by bacteria-like microbes under the surface. Suppose we were to discover that biology, not geology, is making the methane. This would be big news, because after centuries of imaginative speculation, we would have found real Martians.

Now consider the long-term problems this would pose. Mars, rather than being a natural place for humankind to explore and exploit, would take on a different mien. Suddenly we'd know it has natives.

So what do we do about that? Some would say, "Hey, these Martians are mindless and miniscule. We don't worry about earthworms at a building site. We won't worry about these guys." Of course, samples of this life would be made available for scientific scrutiny, but that's a different, and short-term, matter. Once the inhabitants had been cataloged and crated, Mars would be open for business. After all, isn't it human destiny to spread out? Surely we wouldn't let a messy mass of microbes interfere with our efforts to colonize the Red Planet.

Or would we? Others might say, "Look, the planet has its own ecosystem. Leave it alone. We'll turn Mars into a nature preserve." If, like NASA's Chris McKay, you think that life is special and should be encouraged, you might wish to intervene to give the indigenous Martian life a helping hand; to let it flourish in a way that's clearly beyond what it's doing now. In other words, not merely preserve the Martians' habitat, but improve it.

Those who cotton to third-way approaches might consider fencing off Mars' inhabited real estate (assuming that it doesn't lace the entire planet), and limiting human intrusion. It's unclear, of course, how well this would work, and in any case, any long-term terraforming project would change the climate in the "Martian territories" as well as the rest of this world.

So what would you do? What should humanity do, and how will it decide? And even if there was some sort of international agreement, who would be tasked with enforcing it?

These are not easy questions to answer, and the organizers of the workshop thought it worth getting a head start before the headlines arrive. Consider the reluctance of Nicolaus Copernicus to publish his work a half-millennium ago. Fearful of the reaction of religious zealots, he initially did no more than circulate a small book, without his name on it, outlining his ideas.  His magnum opus, De Revolutionibus Orbeum Coelestium, hit the shelves (and, according to popular account, his deathbed) much later. Similarly, Charles Darwin delayed publication of his evolutionary theories, worrying that they would discomfit readers because humankind would no longer be so exceptional. Societal reaction can matter.

The fact is that much of what scientists do won't change your life very much. A lot of it is like numismatics or canning fruit: specialized activities with only modest cultural impact. But if we find life of any kind beyond Earth, everyone's going to notice, and our descendants will be affected in profound ways. Exactly how they'll be affected deserves our consideration now.


http://www.space.com/searchforlife/0902190-seti-finding-life-impacts.html

[gladys2]

No doubt about it, given the numbers and the odds there are probably several XNC2 groups operating on other worlds.

[DazzaMc]

lol...

Wonder what they bitch and moan about?

[bump head benny]

 

[bump head benny]