Habitable Worlds, Homer, and Haldane — or — Ganymede's Oceans, and Imagining Kepler-186f's Sunsets

Scientists at the University of Puerto Rico at Arecibo's Planetary Habitability Laboratory simulated Kepler-186f's sunsets.

Others studied possibly-habitable regions in Jovian moons and around double stars. Meanwhile, some chap at Oxford trotted out opportunities for angst and dread.

1. Oceans in Ganymede
2. Ganymede: Water, Rock, and (Maybe) Life
   • "Salt" isn't Always "Salt"
   • Bidirectional "Snow"
   • Ice I Through XV: Water, Physics, and Life
   • Water Worlds, Life, and a Mission to Jovian Moons
   • Martians, Dying Worlds, and Assumptions
3. Space Aliens May Not be Human — or — "the Great Filter" and Haldane
   • Horses, Humans, and Attitude
   • Smörgåsbords and Crazy Uncle Eddy
4. Kepler-186f: What About Sunsets?
   • Sunset Stroll on an Alien Beach
5. Life on Moons with Two Suns?
   • Close Binaries and Habitable Zones
   • Circumbinary Planets: and Moons
   • Habitable Moons, Cruise Ships, and Homer's "Odyssey"

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Fire, String, and Other Dangerous Technology

(From WiNG, via Wikimedia Commons, used w/o permission.)

"Human nature will not change. In any future great national trial, compared to the men of this, we shall have as weak and as strong, as silly and as wise, as bad and as good."
Abraham Lincoln, Response to a serenade (November 10, 1864)

Over the last million years, we've learned to use fire without killing ourselves, weren't cut to shreds by flint tools, and developed an alternative to horse-drawn wagons before burying London in manure.

If anything, we're smarter now than we were in the 'good old days:' so I don't think that steam engines or integrated circuits will kill us all. (November 22, 2013; July 9, 2011)

The trick is using humanity's accumulated wisdom, and applying it to everyday life. Most of the time, we do a pretty good job: my opinion.

Sometimes mistakes are made. Then, most of the time, we clean up the mess and move on.

Cities don't burn as regularly as they once did, but urban fires still happen: like the Camden Market fire and Lac-Mégantic derailment. We're learning that liquid propane gas heaters aren't entirely safe; and that leaving a trainload of flammable material unattended isn't a good idea.

The problem isn't the tech: it's us.

"For mischief comes not out of the earth, nor does trouble spring out of the ground;

"² But man himself begets mischief, as sparks fly upward."
(Job 5:6-7)

A million years from now,¹ my guess is that we'll still have trouble when someone gets careless with fire. But I don't think we'll abandon 'dangerous' tech like fire, string or autonomous robots. (April 27, 2014; February 25, 2014)


(From Indolences, via Wikimedia Commons, used w/o permission.)

Working Toward Perfection

(From NASA, ESA, and The Hubble Heritage Team, used w/o permission.)

This isn't a perfect world. The universe is in a "state of journeying" toward an ultimate perfection. (Catechism of the Catholic Church, 310)

Part of our job is bringing ourselves, our societies, and our world, closer to that perfection. (Genesis 1:26-27; Catechism, 355, 337-349, 1928-1942, 2415)

Learning more about this creation, and developing new ways to manage and use it, are part of being human. Science and technology aren't transgressions, they're tools we're supposed to use: wisely. (Catechism, 2292-2296)

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1. Oceans in Ganymede

(NASA/JPL-Caltech, via Reuters, used w/o permission.)
"This artist's concept of Jupiter's moon Ganymede, the largest moon in the solar system, illustrates the ''club sandwich'' model of its interior oceans."

"Jupiter's moon Ganymede may have 'club sandwich' layers of ocean"
Will Dunham, Reuters (May 2, 2014)

"As club sandwiches go, this undoubtedly is the biggest one in the solar system.

"Scientists said on Friday that Jupiter's moon Ganymede may possess ice and liquid oceans stacked up in several layers much like the popular multilayered sandwich. They added that this arrangement may raise the chances that this distant icy world harbors life.

"NASA's Galileo spacecraft flew by Ganymede in the 1990s and confirmed the presence of an interior ocean, also finding evidence for salty water perhaps from the salt known as magnesium sulfate....

"...Steve Vance, an astrobiologist at NASA's Jet Propulsion Laboratory in California, said the arrangement might be like this: at the top, a layer of ice on the moon's surface, with a layer of water below that, then a second layer of ice, another layer of water underneath that, then a third layer of ice, with a final layer of water at the bottom above the rocky seafloor.

" 'That would make it the largest club sandwich in the solar system,' Vance said in a telephone interview. 'I suppose I'm also a fan of club sandwiches. My fiancée points out that I order them every time we go out to eat.'..."

Ganymede is the largest moon in the Solar system: 3,300 miles, 5,300 kilometers, in diameter; bigger than Mercury. That's less than half the size of Earth, but since its underground ocean is hundreds of miles deep, Ganymede has a great deal more water than our planet.

Ganymede is one of the Jovian moons discovered by Galileo, and the only moon we know of with its own magnetosphere. The most likely explanation is that Ganymede has a liquid iron core with convection currents.

This moon also has an oxygen atmosphere: a very thin one. This isn't a sign of life. There's a bit of water on the surface, exposed to radiation that splits it into hydrogen and oxygen atoms. Hydrogen's atomic mass is quite a bit lower than oxygen's, so it 'evaporates' faster, leaving a barely-detectable oxygen haze.

---

2. Ganymede: Water, Rock, and (Maybe) Life

(From NASA/JPL-Caltech, used w/o permission.)
("...This artist's concept of Jupiter's moon Ganymede, the largest moon in the solar system, illustrates the 'club sandwich' model of its interior oceans. Scientists suspect Ganymede has a massive ocean under an icy crust. In fact, Ganymede's oceans may have 25 times the volume of those on Earth.")

"Ganymede May Harbor 'Club Sandwich' of Oceans and Ice"
NASA/JPL press release (May 1, 2014)

"...Ganymede's ocean might be organized like a Dagwood sandwich,' said Steve Vance of NASA's Jet Propulsion Laboratory in Pasadena, Calif., explaining the moon's resemblance to the 'Blondie' cartoon character's multi-tiered sandwiches. The study, led by Vance, provides new theoretical evidence for the team's 'club sandwich' model, first proposed last year. The research appears in the journal Planetary and Space Science.

"The results support the idea that primitive life might have possibly arisen on the icy moon. Scientists say that places where water and rock interact are important for the development of life; for example, it's possible life began on Earth in bubbling vents on our sea floor. Prior to the new study, Ganymede's rocky sea bottom was thought to be coated with ice, not liquid -- a problem for the emergence of life. The 'club sandwich' findings suggest otherwise: the first layer on top of the rocky core might be salty water.

" 'This is good news for Ganymede,' said Vance. 'Its ocean is huge, with enormous pressures, so it was thought that dense ice had to form at the bottom of the ocean. When we added salts to our models, we came up with liquids dense enough to sink to the sea floor.'..."

The first models of Ganymede's oceans assumed that its salt didn't affect water's properties. I'm sure that scientists 'knew better,' but they had to start somewhere. Creating a mathematical model for a global ocean is far from simple.

"Salt" isn't Always "Salt"

When I say "salt," I generally mean sodium chloride: the most common salt in Earth's ocean.

To a chemist, "salt" is an ionic compound that can result from the neutralization reaction of an acid and a base: which may be more than you wanted to know about chemistry.

Magnesium sulfate, another salt, isn't exactly rare on Earth. I've got a bag of it in the house: labeled "Epsom salt." Moving on.

Bidirectional "Snow"

(From NASA/JPL, via Wikimedia Commons, used w/o permission.)
(Image of Ganymede, taken by the Galileo spacecraft (June 26, 1996))

Bear with me, please. This excerpt's on the long side: but the second paragraph is a pretty good description of what may be going on in Ganymedian oceans.

"...The models get more complicated when the different forms of ice are taken into account. The ice that floats in your drinks is called 'Ice I.' It's the least dense form of ice and lighter than water. But at high pressures, like those in crushingly deep oceans like Ganymede's, the ice crystal structures become more compact. 'It's like finding a better arrangement of shoes in your luggage -- the ice molecules become packed together more tightly,' said Vance. The ice can become so dense that it is heavier than water and falls to the bottom of the sea. The densest and heaviest ice thought to persist in Ganymede is called 'Ice VI.'

"By modeling these processes using computers, the team came up with an ocean sandwiched between up to three ice layers, in addition to the rocky seafloor. The lightest ice is on top, and the saltiest liquid is heavy enough to sink to the bottom. What's more, the results demonstrate a possible bizarre phenomenon that causes the oceans to 'snow upwards.' As the oceans churn and cold plumes snake around, ice in the uppermost ocean layer, called 'Ice III,' could form in the seawater. When ice forms, salts precipitate out. The heavier salts would thus fall downward, and the lighter ice, or 'snow,' would float upward. This 'snow' melts again before reaching the top of the ocean, possibly leaving slush in the middle of the moon sandwich.

" 'We don't know how long the Dagwood-sandwich structure would exist,' said Christophe Sotin of JPL. 'This structure represents a stable state, but various factors could mean the moon doesn't reach this stable state.'

"Sotin and Vance are both members of the Icy Worlds team at JPL, part of the multi-institutional NASA Astrobiology Institute based at the Ames Research Center in Moffett Field, Calif...."
(NASA/JPL press release)

I like the mental image of Ganymedian precipitation 'falling' in opposite directions: ice going up; salts going down. Aesthetic aspects aside, if Ganymede's oceans act this way, we may find living critters: safely tucked between sheets of exotic ice.

Exotic to us, anyway. I'll get back to that.

More:

• NASA Astrobiology Institute
  • Articles
    • "Vitamin B3 Might Have Been Made in Space, Delivered to Earth by Meteorites"
      Bill Steigerwald (May 6, 2014)
    • "Earth's Crust Younger Than Moon-Forming Impact"
      Daniella Scalice (April 28, 2014)
    • "Odd Tilts Could Make More Worlds Habitable"
      Elizabeth Zubritsky(April 23, 2014)
  • Icy Worlds

Ice I Through XV: Water, Physics, and Life

(From Cmglee, via Wikimedia Commons, used w/o permission.)
(Phase diagram of water as a log-lin chart with pressure from 1 Pa to 1 TPa; and temperature from 0 K to 650 K.)

Water is — odd — stuff. At temperatures and pressures found within a few miles of Earth's surface, it's found in one of three phases: solid, liquid, or gas.

Thanks to the many hydrogen bonds between water molecules, it has a high specific heat capacity and heat of evaporation. Water won't melt, freeze, or evaporate, unless a lot of energy transfers in or out. That's good for us, since Earth's relatively abundant water helps moderate temperatures.

Even better, when water freezes at or near Earth's surface: it forms "Ice I," which is less dense than liquid water. If water acted like most substances, becoming denser when it freezes, ice would fall to the bottom of oceans and lakes. As it is, Ice I forms a nice insulating layer above cold, but still liquid, water: usually preventing bodies of water from freezing solid.

On top of that, water dissolves just about everything, given time. Other substances are good solvents, too, like acrylonitrile (CH₃CN): but they're nowhere near as common as water.

Liquid water is an excellent medium for the formation of the complex carbon compounds that run life's processes. Some scientists worked out ways for ammonia to do water's job: or, more likely, a water-ammonia mix.

I've run into a list of plausible, if unlikely, possible life chemistries. (March 7, 2014)

Water Worlds, Life, and a Mission to Jovian Moons

(From Lucianomendez, via Wikimedia Commons, used w/o permission.)
(A hypothetical ocean planet with two satellites.)

The NASA/JPL press release points out that what we're learning about Ganymede can be applied to exoplanets. They site the proposed "water worlds:" rocky planets, more massive than Earth, covered by very deep oceans.

I think applying studies of Ganymede to the moons of 'warm Jupiters' makes sense, too. Come to think of it, a massive moon of a Jupiter-size planet might have liquid water: even if the planet received as little light as the asteroid belt or Jupiter get in our Solar system. Think a moon like Ganymede or Europa.

I'd be very surprised if we find living critters in Ganymede or Europa: but I won't be shocked if we do. Scientists are learning that life thrives in a remarkable range of environments.

I'd also be very surprised if we don't continue learning about this astonishing creation's diversity.

We may learn that we are alone in the universe: that life exists only on Earth, and on the worlds we terraform. Or we may learn that critters are strewn among the stars, each suited to a niche on — or in — their world. I think the latter is more likely: at least, I hope so.

We may learn that we're the exotic creatures: unsupported by water, enduring crushing gravity, exposed to barely-filtered radiation from our star; not living nice, normal lives in a moon's cozy oceans.

Meanwhile, the European Space Agency is working on a space mission with a catchy name: JUpiter ICy moons Explorer; or JUICE.

JUICE is scheduled to launch in 2022, visiting Europa, Callisto and Ganymede in the 2030s. NASA and JPL are contributing to three instruments on the mission. (see www.jpl.nasa.gov/news/news.php?release=2013-069)

Martians, Dying Worlds, and Assumptions

(From Frank R. Paul, via Wikimedia Commons, used w/o permission.)
(Martians, as imagined in Amazing Stories (August 1927))

The Mars in stories like "The War of the Worlds," Burroughs' Barsoom tales, and "Quatermass and the Pit/Five Million Years to Earth," is a Lowellian world: slowly dying; or dead.

I have no problem with stories of Barsoom, although Mariner 4's 1965 flyby showed a planet only slightly less hospitable than Earth's moon: and no trace of Martian princesses. More recently, we've learned that Mars is probably damp, if not wet, at least in spots: and that's another topic.

Drama depends on conflict, and "man against nature" serves this purpose: or Martian against nature, as the case may be.

How folks react under stress can be a story starter for anything from a potboiler adventure tale, to "The Brothers Karamazov." My "Waiting on a Dead World" shows some options: ethical and otherwise. If you read it, bear in mind that I posted it on Halloween.

As long as an author weaves a good yarn, I don't mind the occasional dying world or horde of Martian invaders.

But I don't assume that the last scene in "Planet of the Apes" represents a probable future. I enjoyed the film in 1968: but that was the '60s, I was in my teens, and 'post-apocalyptic' depression fests hadn't become a cinematic mainstay. (Drifting at the Edge of Time and Space (January 26, 2010))

I'm nowhere near pessimistic enough to be taken seriously among folks whose goal in life seems to be finding the dark linings of silver clouds. I've discussed conventional pessimism and the big picture a few times, including:

• "Scorpions, Acid Rain, and the Great Dying"
  (November 29, 2013)
  Particularly
  • Prophets of Doom
• "Seeing the Horizon"
  (May 19, 2013)
• "Hope, Joy, and 'More Despondent Than Thou?' "
  (January 8, 2012)

Most of what I've read about Kepler-186f has been serious: the thoughtful kind, not the gloomy sort of serious that's fashionable in some circles.

Predictably, one 'expert' decided that if many planets may harbor life: we're doomed. Perhaps I'm being unfair:

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3. Space Aliens May Not be Human — or — "the Great Filter" and Haldane

(From NASA Ames/SETI Institute/JPL-CalTech, via Space.com, used w/o permission.)
"Let's hope it's barren."

"Habitable Exoplanets are Bad News for Humanity (Op-Ed)"
Andrew Snyder-Beattie, University of Oxford; Live Science's Expert Voices: Op-Ed & Insights, via Space.com (April 26, 2014)

"This article was originally published at The Conversation. The publication contributed the article to Live Science's Expert Voices: Op-Ed & Insights.

"Last week, scientists announced the discovery of Kepler-186f, a planet 492 light years away in the Cygnus constellation. Kepler-186f is special because it marks the first planet almost exactly the same size as Earth orbiting in the 'habitable zone' – the distance from a star in which we might expect liquid water, and perhaps life.

"What did not make the news, however, is that this discovery also slightly increases how much credence we give to the possibility of near-term human extinction. This because of a concept known as the Great Filter...."

The idea, apparently, is that if many planets could support life, humanity will probably go extinct: soon.

I haven't heard this conventional pessimism called "the Great Filter" before, but the basic idea goes back several decades, at least.

The Oxford chap may be right: but I don't think so.

Andrew Snyder-Beattie's argument, as I understand it, goes like this. We haven't run into space aliens, or evidence that a thriving interstellar civilization exists, so either:

• Very few planets support life
• Life is common but intelligent life is very rare
• Intelligent life doesn't last long

I might agree with him, if I assumed that intelligent life would always be just like us humans: and took today's conventional pessimism seriously.

Folks still scared silly by the Cold War, terrified by "Silent Spring," or who haven't noticed that Ehrlich's population bomb fizzled, might assume that we're about to kill ourselves off. I've got too good a memory to take the crisis du jure seriously.

More of my take on 'End Times Bible Prophecies' and their secular analogues:

• "Human Folly and Body Counts"
  (February 25, 2014)
• "Global Warming, End Times - 'We're All Gonna Die' Over the Last 45 Years Or So"
  (October 3, 2009)

As I see it, the Oxford fellow says that we haven't met space aliens yet for at least one of the following reasons:

• Life can only exist on planets just like Earth
• Humanity is the only possible form of intelligent life in the universe
• Technology has doomed us all

I'm guessing that the universe isn't as bland — or depressing — as all that. I'm also dubious that, having survived fire, flint tools, steam engines, and alternating current, the latest crop of inventions will do us in.

I also think it's very likely that if we meet neighbors in the universe — they won't be human.


(From NOAA, via Wikimedia Commons, used w/o permission.)

As Haldane said:

"I have no doubt that in reality the future will be vastly more surprising than anything I can imagine. Now my own suspicion is that the Universe is not only queerer than we suppose, but queerer than we can suppose."
(J. B. S. Haldane, Wikiquote)

Horses, Humans, and Attitude

I've speculated about what people who aren't human might be like: not so much their appearance, as how they might think.

We may discover that the universe abounds with nice, normal, sane people: who enjoy a quiet life, and never considered leaving the familiar safety of their homes. They may already know about us: and think that if they are very quiet, we may go away.

This is speculation, of course: we still don't know if there's life anywhere else in the universe, let alone living creatures who are people.

But if we do have neighbors, I think it's quite likely that they're not designed exactly the same way we are. In my 'writer' blog, I've played with a few alternatives, including this discussion that started after I'd read what some fellow said about horses:

The part that's relevant to this blog is the section headed "Herd Mentality:" discussing the way horses think.

They're not human.

Faced with danger, horses run.

Faced with danger, or something we don't like, we're likely to do what most primates do: scream and start throwing things. (Ever see news video of a violent mob?)

Horses like things to be quiet.

Not everybody's as noisy as Americans — and, I understand, Australians. But one thing that human beings are not is quiet. Not compared with most creatures....

...Sure, on Earth the people are screaming, stuff-throwing primates: but that doesn't mean that's the only way things can work.

(Drifting at the Edge of Time and Space (December 9, 2009))

Smörgåsbords and Crazy Uncle Eddy

(From by bjaglin, via Wikimedia Commons, used w/o permission.)
(A little of this, a little of that: from a smörgåsbord.)

One of the big differences between us and horses, physically, is that they're herbivores: we're opportunistic omnivores.

We can survive on a plants-only diet: but we're designed to eat just about anything we can catch and cook, plus whatever fruits, nuts, berries or — sometimes — bark, the local smörgåsbord offers.

I suspect our ability to eat pretty much anything, plus getting started during one of Earth's ice ages, helped shape how we think and act.

Maybe there's nobody else out there, or maybe most people live on planets where it's really, really hard to get into orbit. Or maybe we live on a planet where, for the last few million years, the environment favored creatures with a bit more brains than usual: who were willing to take insane risks.

Like flying.

Or riding a tower of explosives to an airless hell of barren rock. Several times.

Across the galaxy, most people may be staying quietly at home, playing the local equivalent of pinochle or Mahjong, or whatever: and shuddering at the memory of crazy Uncle Eddy, who once made something he called a "raft," but - thankfully - never tried using it himself.
(Apathetic Lemming of the North (December 5, 2009))

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4. Kepler-186f: What About Sunsets?

(From University of Puerto Rico at Arecibo / NASA, via c|net, used w/o permission.)
"A comparison of Earth and Kepler-186f as a cold world with shallow oceans."

"How a sunset might look on Earth's new cousin Kepler-186f"
Eric Mack, c|net (April 17, 2014)

"NASA confirms the discovery of an Earth-sized planet that may have potential for life, but its sun is dimmer than ours. Here's what an evening stroll on a beach on Kepler-186f might be like.

"NASA announced Thursday that it has confirmed the first planet beyond our solar system that exists in the habitable zone of its star and is close to the size of Earth, making it the most likely exoplanet yet validated to host life. But the planet, Kepler-186f, orbits an M-class dwarf star and receives only about a third of the energy from its sun that Earth receives from our own beloved fireball.

"That means it could be a frozen, Hoth-like world, or it could be more dry and dead like Mars. But if conditions are right and liquid water exists on Kepler-186f, as NASA thinks it might, it could look more like the above conception, a slightly more chilly version of Earth with shallow oceans.

"This, naturally begs the question: What does a sunset look like when you get that much less photon love from your neighborhood solar furnace?...

Eric Mack is right: we still don't know if Kepler-186f has an atmosphere, let alone water. It might resemble Hoth, from the Star Wars stories: but Hoth looks a lot like parts of Norway, one of my ancestral homelands: and that's yet again another topic.

Kepler-186f's high noon sunlight would be a big like sunlight on Earth an hour before sunset: so yes, the climate will be on the nippy side for humans, at best.

Kepler-186f's star isn't just smaller than our Sol: it's cooler, too: about 3,788° Kelvin, compared to our star's 5,778° Kelvin. Besides getting about a third as much light as Earth, sunlight on Kepler-186f would be a bit on the reddish side.

Sunset Stroll on an Alien Beach

(From University of University of Puerto Rico at Arecibo / PHL, via c|net, used w/o permission.)
"A Kepler-186f sunset appears dimmer, but the sun is larger."

"... Fortunately the folks at the Planetary Habitability Laboratory of the University of Puerto Rico at Arecibo are much more obsessed with exoplanets than even the Crave crew -- they mocked up the below comparison of a gorgeous Caribbean sunset as it appears on Earth, and how a similar spot might look if it were relocated to Kepler-186f at dusk.

"I love this visualization because it really drives home the relevance of an otherwise abstract discovery. Nothing like the notion of a sunset stroll on an alien beach to make you feel even smaller, but perhaps also less alone...."
(Eric Mack, c|net)

Whether or not someone felt smaller while strolling on the (hypothetical) beaches of Kepler-186f would probably depend on the person's outlook on life, the universe, and everything.

If the stroller came from Earth, he or she would feel heavier, though, since Kepler-186f is about 10% bigger than Earth. To have beaches, the planet would have to have pretty close to Earth's density: so the surface gravity would be a tad higher than we're used to.

I made a very rough estimate of Kepler-186f's surface gravity by assuming that it's a dense as Earth. With a diameter 1.11 times our home, Kepler-186f's volume is about 1.37 times Earth's. If it's made of exactly the same mix of rock and metal, it'd be denser: but this is a rough estimate, so I'll say that it's 1.37 times Earth's mass.

Plugging these numbers into g = m/r², where g is surface gravity, m is mass, and r is radius; all with Earth=1; I got a surface gravity for Kepler-186f of about 1.11 g. We'd feel heavier there, but I think it'd be manageable.

Someone weighing 150 pounds here would have about 166 pounds pressing on the sands of that hypothetical beach.

---

5. Life on Moons with Two Suns?

(From NASA/Kepler Mission/Dana Berry, via Astrobiology Magazine, used w/o permission.)
"The habitable zones of single stars are larger and wider as the temperatures increase. Although hotter stars have the widest regions where water can lie on the surface, they also have short lifetimes that limit the ability of life to evolve."

"Two Suns Could Make More Habitable Moons"
Nola Taylor Redd, Astrobiology Magazine (March 23, 2014)

"Moons in close binary solar systems have a better chance of hosting life than those in single-star systems, new research has shown.

"Binary stars dampen each other's solar radiation and stellar winds, thereby creating a more hospitable environment for life and increasing the habitable zone around such solar systems, according to research presented at the 223rd American Astronomical Society meeting in January....

We're pretty sure that it takes several billion years for life to go from single-cell critters to people like us. At least, that's how long it took here on Earth. Maybe we were fast-tracked, maybe not: or maybe we're alone in the universe.

Stars hotter than ours have "short" lifetimes only when compared to Sol or red dwarfs. Even a spectral class O3 star, 60 times as massive as ours, burns for about 3,000,000 years. Unless what scientists have learned about the universe over the last century is completely wrong: which does not seem likely.

Although this study focuses on the odds of finding habitable moons, I think it's interesting — and hopeful — that close binary stars with lower mass burn longer and have larger habitable zones.

Close Binaries and Habitable Zones

(From NASA/Kepler Mission/Wendy Stenzel, used w/o permission.)
("NASA's Kepler spacecraft has found over 5,000 potential planets, most of which will likely be confirmed. Scientists have combed through the list in search of the best planets to hunt for exomoons around.")

"...'The two stars calm each other down in terms of activity, said Paul Mason, an astrophysicist at the University of Texas at El Paso in an interview with Astrobiology Magazine....

"...Although more than a thousand planets have been found outside of the solar system, as well as a host of candidates waiting for follow-up observations, no moons have yet been confirmed. Scientists like Mason are performing theoretical calculations to determine which solar systems might be better for hosting potentially habitable moons.

"Violent and active young stars spin rapidly, emitting radiation and stellar winds that could interfere with the habitability of planets and moons nearby. A close binary system of stars can help to dampen these effects, as the two stars synchronize their spins.

"Binary stars exist in a range of configurations. Some are widely separated, so that a planet in orbit around one functions much like a planet around a single sun, while the companion is so distant that it appears as point-like as any other star. Others may be extremely close together, synching together to keep each other rapidly spinning for billions of years...."
(Nola Taylor Redd, Astrobiology Magazine)

More good news: again, from my point of view. Close binaries not only have wider habitable zones: the stars tend to shine more evenly than their solo counterparts.

It looks like there's a lot more real estate out there that's got a chance of supporting life.

Circumbinary Planets: and Moons

(From NASA/ESA/K. Retherfod/SWRI, used w/o permission.)
("Astronomers recently found evidence of plumes of vapor coming off of Jupiter's moon Europa. Europa is thought to house an ocean under an icy surface, making it one of the best potential sources for life in the solar system.")

Mason's research focuses on circumbinary systems: a fancy name for planetary systems where two stars orbit each other, and at least one planet orbits both stars. He's looking at circumbinary systems where the stars orbit each other between 10 and 60 days.

These circumbinary systems should be better homes for life than single-star ones like ours. The stars exert tidal forces on each other, slowing their rotation rates: reducing the harmful radiation and stellar wind the pair emit.

Fast stellar winds can blow a moon or planet's atmosphere into space. The farther a planet is from its star, the more moderate the stellar winds. As a sort of bonus, with two stars the pair's habitable zone is wider than for a single star of similar brightness.

Moving farther out makes it easier for planets to hang onto their moons, too.

Habitable Moons, Cruise Ships, and Homer's "Odyssey"

"...'The closer a planet is to the star, the smaller its gravitational sphere of influence,' said David Kipping and astronomer at the Harvard-Smithsonian Center for Astrophysics in an interview with Astrobiology Magazine.

" 'Essentially, the star will rip off the moon if it gets too close, he said.

"Kipping, who was not involved in the research, searches for exomoons and is the principle investigator of The Hunt for Exomoons with Kepler project.

"Pushing exomoons farther away also has ramifications for red dwarfs, the most populous stellar type in the galaxy. The habitable zone around these smaller, long-lived stars is so close to its parent star that stellar activity made many astronomers consider habitable planets around them unlikely to even exist, though recent research has increased the potential. In a binary system, the pushed-back habitable zone would decrease many of the negative effects that limit habitability around the plentiful stars...."
(Nola Taylor Redd, Astrobiology Magazine)

Maybe the first habitable exoplanet we find won't be a planet at all: but an exomoon.

Seen from a habitable moon's surface, the planet might look a great deal larger than our moon. Between sunsets reminiscent of William Ascroft's sketches, and a dramatically outsize moon: the scenery might encourage tourism.

Ridiculous? Maybe: but so would the idea of cruise ships have been, 28 centuries back, when Homer's "Odyssey" was new.

Related posts:

• Planets and people
  
  • "The Search for Life: Earth-Size Planet, in the Habitable Zone — Found"
    (April 25, 2014)
    Particularly
    • The Quest for Life: and Neighbors
    • Right Size, Right Temperature: Kepler-186f Might Support Life
  • Life in the Universe: Focusing the Search"
    (April 18, 2014)
    Particularly
    • Perceptions
    • Defining "Persons"
    • Would I Baptize an Extraterrestrial?
  • "Strange New Worlds; Getting a Grip about Space Aliens; and a Fossil Fish"
    (January 17, 2014)
    Particularly
    • Space Aliens, Elvis, and a Baleful Bat Child
    • Rungs on the Ladder of Creation
  • "DNA Components, an Asteroid, and Life on a Wobbling World"
    (February 21, 2014)
    Particularly
    • Scorpions, Cockroaches: and Humans
    • Getting a Grip About "Class M" Planets
  • "The Eight-and-a-Half-Hour Year of Kepler 78b, and the Seven Worlds of KIC 11442793"
    (November 1, 2013)
    Particularly
    • "Earth-Like," Minnesota, Finland, and Me
• Technology
  • "Lowering Costs on the Earth-to-Orbit Run, Preparing for Incoming Asteroids"
    (May 2, 2014)
    Particularly
    • Looking Ahead
  • "Kepler-69c and Habitable Zones; The Great Martian Land Rush"
    (October 25, 2013)
    Particularly
    • Crackpots, Dreamers, and NASA Design Studies
    • The Ethics of Terraforming
  • "Fusion Power, Terraforming, and Old Dutch Windmills"
    (October 11, 2013)
    Particularly
    • Terraforming and Windmills
    • "Shell Worlds"
  • "Love, Technology, and Being Human"
    (October 6, 2013)
  • "Warp Drive: Imagined and Real (Maybe, Eventually)"
    (May 24, 2013)
    Particularly
    • Weird Physics, Warp Drive, News, and NASA
• Speculation
  • "Old Water, Older Fossils, and Extraterrestrial Etiquette"
    (November 15, 2013)
    Particularly
    • Space Aliens
    • Interstellar Diplomacy and Ignoring Strict Guidelines
  • "Beware Warmonger Imperialist Space Aliens!?"
    Apathetic Lemming of the North (January 11, 2011)
  • "Gods, Demons, and Used Spaceship Dealers"
    Drifting at the Edge of Time and Space (February 13, 2010)
  • " 'All We Want is Peace and Quiet' - Another Look at the Mind of the Alien"
    Drifting at the Edge of Time and Space (December 9, 2009)
  • "Earth May Not Be a 'Class M' Planet"
    Apathetic Lemming of the North (December 5, 2009)
    Particularly
    • "...Superior Alien Civilizations
    • Doesn't Everybody Dream of Flying?

---

¹ A million years?? I don't go along with today's conventional pessimism. I'm guessing that we're at least as resilient as scorpions, cockroaches, and rats. (November 29, 2013)