Extrasolar Moons being Earthlike??

[neilsox]

Re: Habitable planet-moon system

I agree binary planet, but conditions for humans to survive naked on both are improbable. With a radius of 7000 kilometers and an average density of 3, the surface gravity would be one g or a bit more. The other could be a radius of 5000 kilometers with an average density of 7 also yields about one g surface gravity. About one g is essential to retain an Earth like atmosphere, if the solar wind is strong. The solar wind at saturn is about 20 times weaker than in the habitable zone. Do some k type and g type suns have weak solar wind? I'm guessing, so correct me if wrong. Neil

 

[AssailantSponge]

Habitable Moon of a Gas giant?

I have seriously doubted the possibility of a moon of a gas giant being habitable, mainly because of the requirements of a habitable planet and a gas giant put together. Is there any theoretical chance of it being possible? :ugeek:

 

[raptorborealis]

Re: Habitable Moon of a Gas giant?

Habitable by ....?

By humans?...with no added technology?

There are an estimated 10,00000000000000000000000 stars in the Universe. The odds of a gas giant with a habitable moon would be extremely rare but that would probably still be quadrillions or so. Add some technology and even one in a million star systems would be 10,0000000000000000 habitable moons...again 'rare'...but quite a few.

 

[AssailantSponge]

Re: Habitable Moon of a Gas giant?

When I say habitable I mean habitable by humans. I mean, I'm not very smart in these things but doesn't a gas giant have to form in the outer reaches of a solar system? Then it would have to migrate inwards to the habitable zone of a star, retain a relatively circular orbit once in the habitable zone, then have a moon with all the ingredients for life. Would the gas giant last long? Because that sounds like it would dissipate from the heat, but by all means correct me if I said anything stupid.

 

[SteveCNC]

Re: Habitable Moon of a Gas giant?

If you mean naked habitable , no .

With technology it would be possible (beyond very expensive) to build a base I believe under the ice shell of europa that could be self-sustainable using one or multi hydrothermal/geothermal/nuclear energy .

 

[Boris_Badenov]

Re: Habitable planet-moon system

About one g is essential to retain an Earth like atmosphere. I'm guessing so correct me if wrong. Neil

The surface gravity of Saturn's moon Titan is .14g & it's surface atmospheric pressure is 146.7 kilo pascals. The average surface pressure on Earth is 101.325 kPa. So, no, you don't have to have 1g to have an atmosphere.
Wouldn't two Earth sized planets in a binary system become tidally locked real quick like?

 

[Astro_Robert]

Re: Habitable Moon of a Gas giant?

I don't see why you couldn't have a gas giant in the habitable zone with a large terrestrial moon containing an atmosphere. We can call this place Endor. (Blue skinned-Carbon Fiber beings are not required, nor any places where it might become Picth Black) :lol:

However, the presence of the Gas Giant creating eclipses in the middle of many of the days might have an impact on any development of a diurnal cycle which many/most lifeforms here on Earth have adjusted to.

I mean what if 'Endor' had a rotation period of 1 day and an orbital period of 1 week. Every week on the same day, 1 part of the plant would have an eclispe as it passed thru the shadow of the giant planet. Their day might be Mon thru Saturday plus eclipse day. But of course every Wed night would be extra romantic with a full-planet evening, as long as werewolves don't howl at planets. :lol:

As far as plausibility, astronomers have in fact identified many 'hot jupiters' that are close in, so presuming that a gas giant could have a stable orbit slightly farther out in the habitablt zone is not unreasonable. If I recall correctly, we have found a couple of systems with gas giants in or just outside the habitable zone.

 

[SpaceTas]

Re: Habitable Moon of a Gas giant?

We have had at least 3 threads on this.

Several Jupiter mass planets have already been found in the habitable zone (where the temperature would be between 0 and 100 deg C).

There are searches using transit timing and duration variations looking for small mass planets and/or earth mass moons of giant planets.

 

[Sycamorefan]

I saw this thred on here and I couldn't resist re-posting a hypothetical, 2 Exomoon, Both habitable for humans, Planetary system I cooked up a few days ago.

OK, here it is! This is what a star system with 2 HABITABLE MOONS should look like by the numbers:
Main Star Choices: M1V (Red Dwarf) or a K4V (Orange) Note, both of these star classes Together are 14 TIMES more plentiful than Yellow Stars!
Planet: #1 -A gas giant/Brown Dwarf with a mass 14x bigger than Jupiter, that orbits the star in an eccentric orbit of 20%, thats .32AU-0.4AU or 41.6M Km - 52.08M Km. Yeah, I know 0.4 AU is just slightly outside the habitable zone of these star types, but I factored in the gravitational tidal effects of this body on my moons and it raised the average surface temp a little!
Planet: #2 - another gas giant 2x larger than Jupiter, that orbits with 15% eccentric at 2.75 AU - 3.16 AU. This planet serves as a asteriod/ comet shield for the exomoons
Planet: #3 - Yes, another gas giant the same size as Saturn, that orbits with a 10% eccentric at 5 AU - 5.5AU. This planet also helps to block out those pesky life killing space rocks!
Planet #4 - I know its getting old, but yes, ANOTHER Gas Giant! This one is appx. the size of Neptune with a 5 % Eccentric at 7 AU - 7.25 AU. Do I really need to Explain this one any further!

Exomoon A around Planet#1: Is a little bigger than mars, but nearly twice the mass. it 5740Km in Diameter, has a Density of 3000Kg/M Sq., A surface gravity of .57G, Has a Mag. Field Strength of .0002 Tesla, Orbits Planet#1 at .011AU (1432200Km) in a nearly circular orbit 22 degrees Inclination N of Planet#1 Equator. It has changing seasons a lot like the Earth and the average day cycle here( on the outward facing side ) is 28 hours, 14 hours of daylight every day!

Exomoon B around Planet#1: Is a little smaller than Venus, 9200 Km Diameter, 4400Kg/ M Sq Density, .7G Gravity, A Mag Field Strength of 0.00015 Tesla ( Earth's is 0.0005 ), Orbits Planet#1 at .02 AU (2604000Km) in a nearly circular orbit at 37 Degree Inclination S of Planet#1 Equator. The average day cycle here is 46 Hours, 23 hours of daylight and seasons like the other exomoon!

I really believe that something similiar to this should be out there, say less than 250 light years away

 

[bdewoody]

We haven't mentioned the one moon in our solar system that is somewhat earthlike, Titan. OK it's way to cold to support any kind of life we can concieve of but there are conditions on Titan that parallel earth to a large degree. And I just read about microbes that are active in ice.

 

[csmyth3025]

We haven't mentioned the one moon in our solar system that is somewhat earthlike, Titan. OK it's way to cold to support any kind of life we can concieve of but there are conditions on Titan that parallel earth to a large degree. And I just read about microbes that are active in ice.

I believe there are liquid methane lakes and rivers on Titan as well as methane rain. I'm not sure how, or if, life could evolve at such low temperatures using methane as a liquid medium rather than water. It would certainly be worth investigating at some point in the (distant) future.

The fact that Titan embodies such a vast and relatively accessible reservoir of nitrogen, water and hydrocarbons makes it very attractive as an interplanetary mining operation since all of these will be valuable to outposts on moons and asteroids as well as orbiting space colonies. Given its resources, Titan may well become the next millenium's economic super power.

Chris

 

[MeteorWayne]

Except it's really really far away, and deep in Saturn's gravity well

 

[csmyth3025]

Except it's really really far away, and deep in Saturn's gravity well

Point well taken. On the other hand, once they get there our astronauts, miners and chemical engineers will probably be able to cook up plenty of fuel to get back out again.

Chris

 

[silylene]

I discussed this in another thread...but seems necessary here again. The big problems with 'habitable' moons of a gas giant orbiting in a habitable zone is that the giant gravity well of the planet acts like a vacuum cleaner, pulling in asteroids from all around.

We now know that Jupiter suffers an asteroid strike perhaps up to about 100 times a year !

http://www.jpl.nasa.gov/news/news.cfm?release=2010-293
""Jupiter is a big gravitational vacuum cleaner," said Glenn Orton, a co-author on the paper and an astronomer at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "It is clear now that relatively small objects, remnants of the formation of the solar system 4.5 billion years ago, still hit Jupiter frequently. "
"Although collisions of this size had never before been detected on Jupiter, some previous models predicted around one collision of this kind a year. Another predicted up to 100 such collisions. Scientists now believe the frequency must be closer to the high end of the scale.

"It is interesting to note that whereas Earth gets smacked by a 10-meter-sized object about every 10 years on average, it looks as though Jupiter gets hit with the same-sized object a few times each month," said Don Yeomans, manager of the Near-Earth Object Program Office at JPL, who was not involved in the paper. "The Jupiter impact rate is still being refined and studies like this one help to do just that.""
Jupiter's inner moons probably also share a very high rate of being struck by incomings, thanks to Jupiter. Recall that the energy of an asteroid strike is = m v^2 The gravitational well of the gas giant increases the impact velocity, and the energy is then squared by this term.

I would not like living on a moon next to a vacuum cleaner. I think the effects of frequent asteroid strikes on the habitable moons of a gas giant would render the moon unihabitable, and destroy all opportunity for any higher lifeform to evolve. An incoming planet-killer with a frequency of perhaps one every million years isn't good for the evolution of anything bigger than a bacterium.

 

[brellis]

hi silylene

I recall reading something about the detection of a very old planetary system experiencing a renewed dust belt that could result in the formation of a second generation of planets. A quieter situation could occur -- a huge Jupiter could completely clean out the asteroids for a period of time allowing habitability on a mellow moon, n'est-ce pas?

 

[BenS1985]

Thinking about this, I was somewhat unsure. Until I remembered that Titan exists.

Then one is to assume that its possible. Although Titan is far from earthlike, it has the primordial elements of earth. I wonder, though, if there are any caveats to Titan's existence, if Saturn was closer to the sun?

Too bad we may not have an exact answer (in terms of real life example) in my lifetime. That is, unless I find out how to live extra long, hehe.

 

[silylene]

hi silylene

I recall reading something about the detection of a very old planetary system experiencing a renewed dust belt that could result in the formation of a second generation of planets. A quieter situation could occur -- a huge Jupiter could completely clean out the asteroids for a period of time allowing habitability on a mellow moon, n'est-ce pas?

Perhaps. This is an uncommon scenario, you know. For the sake of argument, let's suppose a second generation stable planetary system formed containing a Jovian, and it did clean out its inner solar system of asteroids.

However, that star probably still would possess analogues of Kuiper and Oort clouds. That Jovian would still be a vacuum cleaner for incoming comets incoming from the fringes of that star, from those clouds. And long period or new comets coming from these distant regions can have a much higher incoming velocity than a simple inner system asteroid. Recall Shoemaker-Levy striking Jupiter, had a moon been unlucky enough to be in the way, that would've caused a succession of 'mellow moon' killers. translational KE = 1/2 m v^2

 

[EarthlingX]

About Titan and probability of life as we know it there :

http://www.sciencedaily.com : Lakes on Saturn's Moon Titan Filled With Liquid Hydrocarbons Like Ethane and Methane, Not Water

ScienceDaily (Sep. 21, 2010)

— Titan, one of Saturn's moons, is the only moon in the solar system with an atmosphere -- ten times denser than the atmosphere of Earth. Five years ago, the Cassini-Huygens mission to Saturn, a collaboration between the European Space Agency and NASA, sent a probe through Titan's atmosphere, revealing that Titan is home to a landscape that includes hills, valleys and most notably lakes.

A researcher involved with the mission, Prof. Akiva Bar-Nun of Tel Aviv University's Department of Geophysics and Planetary Sciences, has now determined the composition of these lakes. Taking into account the chemical components of Titan's atmosphere, he has demonstrated that the lakes are not composed of water but contain liquid hydrocarbons like ethane and methane, which are also found in oil and gas wells on Earth.

...

"Titan's unique atmosphere does not include nitrogen and oxygen like Earth's, but rather nitrogen and methane," Prof. Bar-Nun says. Solar irradiation of the methane in Titan's atmosphere produces a variety of hydrocarbon gases, which condense in the atmosphere and fall to the surface of Saturn's moon.

"Upon reaching the cold surface, they liquefy, raining down, flowing through the gullies and accumulating into lakes -- but you wouldn't want to jump into them on a summer holiday," he continues. Further solar irradiation of these hydrocarbons in the atmosphere also produces tiny globules of polymers, or aerosols, which give Titan its famed orange glow.

The chemical processes on Titan are different than those on Earth because there is no water vapor in Titan's air, leading to hydrocarbon-based lakes unlike those seen on our planet. Because of this, the frequent claims that Titan could be a laboratory for the investigation of life's emergence on Earth are unfounded, he says.

...

R. Jacovi, D. Laufer, V. Dimitrov, A. Bar-Nun. Chemical composition of simulated Titan's midatmospheric aerosols. Journal of Geophysical Research, 2010; 115 (E7) DOI: 10.1029/2010JE003585

 

[aaron38]

A naked habitable gas giant moon may be possible given the right conditions. It's going to come down to orbital mechanics.

Assume that any moon of a gas giant is tidally locked. To get an acceptable day/night cycle for plant growth and atmosphere thermal management, the orbital period should probably not be greater than 3-4 days. Europa's period is 3.5 days, and it lies just outside Jupiter's radiation belt, so that distance should be acceptable.

Next, to be long term habitable with a stable atmosphere, the moon needs to be large enough to have it's own magnetic field, plate techtonics and volcanism. Assume a minimum lunar mass of 0.7g. Any smaller and the core will freeze out. The moon's magnetic field will also shield the surface from the radiation belt. However a Jupiter mass at 1AU would collect even more radiation from a G2 star. Would the radiation belt swell, or remain confined to the same volume?

I don't know the orbital mechanics, can a large earth mass orbit jupiter in a three day orbit, or will that mass automatically require a more distant orbit? And the smaller the gas giant, the greater the orbital period as well, correct?

The other complicating factor will be the moon's long term axial stability. If the axis is constantly being tossed about, the surface climate will be chaotic, making it difficult for advanced lifeforms to have the stable environments needed. Life may be mitigated to simple bacteria, as is theorized would be the case with Earth without the Moon.

If the 3-4 day orbit is stable, the conditional habitability should be possible. But it's a long shot. Personally, I think any system with a hot Jupiter is a no-go for finding habitable worlds.

 

[3488]

Excellent post aaron385,

My own thiought is that if there was a Jupiter clone at 1 AU, the radiation belts will be narrower & closer together & closer to the planet, but they will be even more lethal than Jupiter's.

My reasoning is that the solar insolence at Earth is 25 times that at Jupiter, so the magnetoshere over the day side will be compressed & closer to the planet.

A Jupiter clone could easily host an Earth massed moon, in fact the Earth is less massive to Jupiter than our own moon is to Earth.

Jupiter = 318 Earth Masses.
Saturn = 95 Earth Masses.
Earth = 81 Moon Masses.

Worth mentioning, Ganymede takes just over 7 days to orbit Jupiter & Callisto nearly 17 days to orbit Jupiter. An Earth clone in orbit around Jupiter in a three day orbit is possible.

However, it is worth reading silylene's post regarding the parent planet's gravity well & how it concentrates & increases velocities of incoming bollides (Comets & Asteroids). Remeber Jupoiter was struck twice this Summer, once in June & once in August. Supposing both hit an Earth clone moon??????? Imagine even ONE impactor from Shoemaker Levy 9 striking an Earth clone moon!!!!!!!!

Also imagine the parent world having other moons, perhaps one being an exo Mars & another an exo Mercury. Imagine tidal influences!!!! Think what powers the volcanoes on Io!!!!! Now increase that force by several magnitudes!!!!!! The exo Earth moon, will have gigantic earthquakes, tsunamis, monstrous volcanoes as well as frequent impacts. Would not be a welcoming place!!!!!

Anything more advanced than Amoeba I think could be ruled out!!!!!

Andrew Brown.