While browsing the webb I've been hearing some rumors about a recent discovery about an earth-like exoplanet. When checking wikipedia I found this article (http://en.wikipedia.org/wiki/Gliese_581) that states that "a planet about 1.5x the size of the Earth discovered in 2007. The latter is notable as it is the first exoplanet discovered which lies within the habitable zone of the star."
I thought this would be all over the news by now, but I have found nothing. The wikipedia article seems a bit unreliable too. I have no idea if this is true or just some kind of hoax. Is there someone here who knows whats going on?

A little use of Google News and here we go:
http://www.zeenews.com/articles.asp?aid=36...=27&sid=ENV

Oh, so it was true. Found nothing on BBC or on any other major site. Guess I should use google news instead
Thanks for confirming it, this is really exciting news.

Well, you have to search for it... so it's good if you see an uniformative blurb at some other site and really want to go digging for meatier articles.

I'm pretty sure this refers to OGLE 2005-BLG-390LB - That's a largish probably icy planet at ~5.5 Earth Masses, ~2.2AU from its sun, probably around 2.4x earth diameter. Surface gravity should be pretty close to Earth's.

Kind of at the extreme limit of "habitable" but arguable.

I don't know, Helvick. The news article, if it's reliable, specifically identifies the star as Gleise 861 while the OGLE object "presumes" that it's orbiting an M-class dwarf. The article also states that the planet's orbital radius is around 0.1 AU. Doesn't sound like they're talking about the same planets.

Noticed the dateline on the article was today as well. If this is for real, the rest of the media should catch fire shortly...

This is the feature story today on Space.com...

http://www.space.com/scienceastronomy/0704..._exoplanet.html

It's now being reported on Space.com and FoxNews.com

Astronomers Believe They May Have Found Earth-Like Planet

Gee, only 20.5 light years away....maybe we should make sure New Horizons' final trajectory is in this direction.

-Mike

You're right - I was caught in a cross post there and hadn't done the Google thing effectively. The story looks like it is hitting the wires after all. Interesting that this Red Dwarf has already been identified as having a Neptune class planet even closer in with a 5 day orbit so this find makes for a really interesting little solar system.

Assuming its all true - I find it odd that the story has hit solely via the PR news wires and not more normal astro news sites. There's nothing on the press pages of ESO, The Geneva Observatory or Astronomy and Astrophysics. Weird but perhaps the press release just leaked a bit ahead of plan.

One of the internet news services had "It's happy New Year every 13 days!" as the link to their story.

Off hand, given the mass and dimensions, I'm guessing 3 to 4 g's of surface gravity. Interesting to speculate what land plants and animals would look like under those conditions. Sea based life might not see that increase in gravity as such a major factor.

I'd fair kill for a link to real data on this - the eternally repeated AP wire story is wearing thin. One or two of the stories are adding that local gravity is around 1.6g .

Does MSNBC count as a real link?

http://www.msnbc.msn.com/id/18293978/

--Greg

Here's a link to the basic data on the Extrasolar Encyclopedia:

http://vo.obspm.fr/exoplanetes/encyclo/sta...l%20581#a_publi

I believe the paper that discusses the discovery is this one:
UDRY S., BONFILS X., DELFOSSE X., FORVEILLE T., MAYOR M., PERRIER C., BOUCHY F., LOVIS C., PEPE F., QUELOZ D. & BERTAUX J.-L. , 2007
The HARPS search for southern extrasolar planets XI.
Astron. & Astrophys. , - , -

It's the last reference for planets around this star, it's recent, and it matches the periodical cited in the news stories. Unfortunately, there's no link to the actual paper or even the abstract.

Bart

Thanks, Bart!

Interesting that the metallicities of red dwarfs seem lower than the solar value. Does this perhaps indicate an enhanced amount of volatiles in the planetary system...?

This paper published just two weeks ago would seem to dispute that:

Planets Formed in Habitable Zones of M Dwarf Stars Probably Are Deficient in Volatiles
http://www.journals.uchicago.edu/ApJ/journ...5.abstract.html

Curiouser and curiouser...I suppose we need to build the most ambitious possible version of TPF to find out for sure!

I recall that there may be other "problems" for the life favorability of planets around red dwarf stars. The habitable zone is very small, meaning the planet must orbit very close to be in it... as is the case announced today. There is a high chance that the diurnal rotation will be locked into a synchronous rotation with its year (like the moon around the earth). This could cause big problems on heating/cooling of the respective hemispheres and drive huge planet-wide storms. Still, if there were calm temperate zones near the day-night terminator, it could provide a lot of time for life to develop and evolve: Red dwarf stars live 10 times longer than our sun.

ESO 22/07 – Science Release
Under Embargo till 25 April 2007 01:00 CEST
Astronomers Find First Habitable Earth-like
Planet
B-Roll - English Statements
Dr. Stéphane Udry
Geneva Observatory, Switzerland
Lead-author of the paper presenting the results
We just announced a very exciting planet that is very much like the Earth. It is a small mass
planet, 5 Earth masses, and the size of the planet is about 1.5 times the size of the Earth.
This planet is very exciting because at the distance of the planet from the star we expect water to
be present on the surface of the planet and when you speak about water you may speak about
life.
This system is as a whole very interesting because it counts three planets, not only one. The first
one was detected two years ago and then we are just announcing this Earth-like planet in the
habitable zone and there is even a third planet, a bit further away, but also a very light planet, 8
times the mass of the Earth.
These detections were made possible thanks to measurements obtained with HARPS, the
instrument that is presently the most precise one in the world to measure radial velocities of stars.
With this instrument we already have detected 11 among the 13 lightest known planets.
The star is what we call a red dwarf, a very small star. It is very close to us, about 20 light years
from the Earth, and this system will be very interesting for future space missions that will look for
life.
To my opinion there are two main goals now in the coming years. The first one will be to get a
real Earth around another Sun and the second one will be to have the picture of a planet next to
another Sun.
Prof. Michel Mayor
Geneva Observatory, Switzerland
HARPS Principal Investigator
Co-discoverer of the first exoplanet in 1995
We have discovered a very low mass planet. In fact it is the lowest mass planet ever discovered:
it is only five times the mass of the Earth. This planet is probably a rocky planet, maybe fifty
percent larger than the earth: So a very low mass planet, orbiting the star with a period of 13
days.
The search for very low mass planets has to be seen in the context of the search for life in the
universe, because we believe that we need small rocky planets to have a chance to have life
development, but in addition we need to have the good temperature and this planet is a very good
site because not only it is probably a rocky planet, but in addition it is exactly at the good distance
from the star to have the temperature where you have liquid water, and so, conditions needed for
life development.
This very interesting planet is not alone orbiting the star, as we have discovered three planets
orbiting the same star. One with a very short period of five days, discovered already two years
ago. A second one, the most interesting one, with a 5-Earth mass and a period of 13 days. And a
third one, a little bit further away, with a period of 84 days and also very low mass: it's only 8
times the mass of the Earth. So it's a full system of low mass planets.
To search for this kind of complex systems with several planets we need a lot of measurements
done during several months, during several years, measuring the velocity of the star from La Silla
observatory in Chile. And evidently this is the result of a collaboration of several colleagues from
the Grenoble Observatory, Geneva, Lisbon and other places.
In the Galaxy most of the stars are very low mass objects. In fact, the star we are discussing is
only one third of the mass of the Sun and it is one of our closest neighbours. It is only about 20
light years from Earth.
This superb detection is directly the result of the quality of the instrument we are using at ESO La
Silla in Chile. The HARPS spectrograph is presently the most precise spectrograph, designed to
detect planets.
Presently we are still not at the limit of the possibility of HARPS. So I can anticipate that we have
the possibility to still detect more smaller planets, maybe 2-Earth masses and so on. And this is a
very challenging goal.
Research in the field of extrasolar planets is very good in Europe and, just to give an example, if
we only consider objects with mass less than 20 times the mass of the Earth, 70% of them have
been discovered in the framework of ESO at La Silla.

ESO PR Photo 22d/07

Velocity Variations of Gliese 581


Three-planet Keplerian model of the Gliese 581 radial-velocity variations. The panels display the phase-folded curve of each of the planets, with points representing the observed radial velocities, after removing the effect of the other planets. Top panel refers to the 15 Earth-mass planet orbiting close to the star (5-d period), the middle one is the 5 Earth-mass planet in the habitable zone and the lower panel shows evidence for a third, 8 Earth-mass planet with a period of 84 days. The error on one measurement is of the order of 1 m/s.

Artist's impressions of the planetary system around the red dwarf Gliese 581. Using the instrument HARPS on the ESO 3.6-m telescope, astronomers have uncovered 3 planets, all of relative low-mass: 5, 8 and 15 Earth masses. The five Earth-mass planet makes a full orbit around the star in 13 days, the other two in 5 and 84 days. © ESO

I'm watching the news wires and this story has been climbing higher all day. Since it's likely going to be reported around the clock, let's all keep our eyes open for examples for the "Inaccuracies in reporting" discussion thread. There's bound to be some fun stuff that will pop up.

ESO 22/07
Under Embargo till 25 April 2007 01:00 AM CEST




Astronomers Find First Habitable Earth-like Planet




Astronomers have discovered the most Earth-like planet outside our Solar System to date, an exoplanet with a radius only 50% larger than the Earth and possibly having liquid water on its surface. Using the ESO 3.6-m telescope, a team of Swiss, French and Portuguese scientists discovered a super-Earth about 5 times the mass of the Earth that orbits a red dwarf, already known to harbour a Neptune-mass planet. The astronomers have also strong evidence for the presence of a third planet with a mass about 8 Earth masses.


This exoplanet - as astronomers call planets around a star other than the Sun – is the smallest ever found up to now [1] and it completes a full orbit in 13 days. It is 14 times closer to its star than the Earth is from the Sun. However, given that its host star, the red dwarf Gliese 581 [2], is smaller and colder than the Sun – and thus less luminous – the planet nevertheless lies in the habitable zone, the region around a star where water could be liquid!


“We have estimated that the mean temperature of this super-Earth lies between 0 and 40 degrees Celsius, and water would thus be liquid,” explains Stéphane Udry, from the Geneva Observatory (Switzerland) and lead-author of the paper reporting the result. “Moreover, its radius should be only 1.5 times the Earth’s radius, and models predict that the planet should be either rocky – like our Earth – or covered with oceans,” he adds.


“Liquid water is critical to life as we know it,” avows Xavier Delfosse, a member of the team from Grenoble University (France). “Because of its temperature and relative proximity, this planet will most probably be a very important target of the future space missions dedicated to the search for extra-terrestrial life. On the treasure map of the Universe, one would be tempted to mark this planet with an X.”


The host star, Gliese 581, is among the 100 closest stars to us, located only 20.5 light-years away in the constellation Libra (“the Scales”). It has a mass of only one third the mass of the Sun. Such red dwarfs are at least 50 times intrinsically fainter than the Sun and are the most common stars in our Galaxy: among the 100 closest stars to the Sun, 80 belong to this class.


“Red dwarfs are ideal targets for the search for such planets because they emit less light, and the habitable zone is thus much closer to them than it is around the Sun,” emphasizes Xavier Bonfils, a co-worker from Lisbon University. Any planets that lie in this zone are more easily detected with the radial-velocity method [3], the most successful in detecting exoplanets.


Two years ago, the same team of astronomers already found a planet around Gliese 581 (see ESO 30/05). With a mass of 15 Earth-masses, i.e. similar to that of Neptune, it orbits its host star in 5.4 days. At the time, the astronomers had already seen hints of another planet. They therefore obtained a new set of measurements and found the new super-Earth, but also clear indications for another one, an 8 Earth-mass planet completing an orbit in 84 days. The planetary system surrounding Gliese 581 contains thus no fewer than 3 planets of 15 Earth masses or less, and as such is a quite remarkable system.


The discovery was made thanks to HARPS (High Accuracy Radial Velocity for Planetary Searcher), perhaps the most precise spectrograph in the world. Located on the ESO 3.6-m telescope at La Silla, Chile, HARPS is able to measure velocities with a precision better than one metre per second (or 3.6 km/h)! HARPS is one of the most successful instruments for detecting exoplanets and holds already several recent records, including the discovery of another ‘Trio of Neptunes’ (ESO 18/06, see also ESO 22/04).


The detected velocity variations are between 2 and 3 metres per second, corresponding to about 9 km/h! That's the speed of a person walking briskly. Such tiny signals could not have been distinguished from 'simple noise' by most of today's available spectrographs.
“HARPS is a unique planet hunting machine,” says Michel Mayor, from Geneva Observatory, and HARPS Principal Investigator. “Given the incredible precision of HARPS, we have focused our effort on low-mass planets. And we can say without doubt that HARPS has been very successful: out of the 13 known planets with a mass below 20 Earth masses, 11 were discovered with HARPS!”


HARPS is also very efficient in finding planetary systems, where tiny signals have to be uncovered. The two systems known to have three low mass planets – HD 69830 and Gl 581 – were discovered by HARPS.


“And we are confident that, given the results obtained so far, Earth-mass planets around red dwarfs are within reach,” affirms Mayor.


High-resolution images and broadcast quality material is available. During the embargo period, please contact Henri Boffin (hboffin@eso.org).
Once the embargo is lifted, the material will be available from http://www.eso.org/outreach/press-rel/pr-2007/pr-22-07.html


More Information
This research is reported in a paper submitted as a Letter to the Editor of Astronomy and Astrophysics (“The HARPS search for southern extra-solar planets : XI. An habitable super-Earth (5 MEarth) in a 3-planet system”, by S. Udry et al.)


The team is composed of Stéphane Udry, Michel Mayor, Christophe Lovis, Francesco Pepe, and Didier Queloz (Geneva Observatory, Switzerland), Xavier Bonfils (Lisbonne Observatory, Portugal), Xavier Delfosse, Thierry Forveille, and C.Perrier (LAOG, Grenoble, France), François Bouchy (Institut d'Astrophysique de Paris, France), and Jean-Luc Bertaux (Service d'Aéronomie du CNRS, France)


Notes
[1] Using the radial velocity method, astronomers can only obtain a minimum mass (as it is multiplied by the sine of the inclination of the orbital plane to the line of sight, which is unknown). From a statistical point of view, this is however often close to the real mass of the system. Two other systems have a mass close to this. The icy planet around OGLE-05-390L, discovered by microlensing with a network of telescopes including one at La Silla (ESO 03/06), has a (real) mass of 5.7 Earth masses. It, however, orbits much farther from its small host star than the present one and is hence much colder. The other is one of the planets surrounding the star Gliese 876. It has a minimum mass of 5.89 Earth masses (and a probable real mass of 7.53 Earth masses) and completes an orbit in less than 2 days, making it too hot for liquid water to be present.
[2] Gl 581, or Gliese 581, is the 581th entry in the Gliese Catalogue, which lists all known stars within 25 parsecs (81.5 light years) of the Sun. It was originally compiled by Gliese and published in 1969, and later updated by Gliese and Jahreiss in 1991.
[3] This fundamental observational method is based on the detection of variations in the velocity of the central star, due to the changing direction of the gravitational pull from an (unseen) exoplanet as it orbits the star. The evaluation of the measured velocity variations allows deducing the planet's orbit, in particular the period and the distance from the star, as well as a minimum mass.

This has been a hot topic in the last few months. The journal Astrobiology recently published a series of papers on the habitability of M dwarfs. Here's a link to one of the abstracts:
http://www.liebertonline.com/doi/abs/10.1089/ast.2006.0124

And if you scroll to the bottom, you will find links to the other papers.

Bart

The Systemic internet group appears to have come to the same conclusions about the existence of this planet well before the announcement:

http://oklo.org/?p=205

If you are interested in extrasolar planets, you might want to join this group and download their console.

Bill

That's a very good point. Anyone have any links to the orbital parameters (at least as far as is known) for these three planets? I'm wonder if tidal heating could also be a factor for this super-Earth.

See also some papers from the latest issue of the journal Astrobiology.

As soon as we build a space based system for clearly discerning this planet (the sooner, the better), we will be able to tell who among the theorist came closest to predicting the actual, at least in one case.

Blast it, I was really off on my gravitational guesstimate. I hope my little post didn't contribute to any "inaccuracies" that may be out there.

Any word (or theoretical guesses) on the orbital eccentricity? Hopefully it's in a fairly circular orbit.

And now Spacedaily.com has been updated, but I can't find so much as a whisper on their web site on this story. Strange ...

I just tried to print that Udry et.al. preprint. I had it on the monitor but it wouldn't print - and now it seems to have vanished. Did anyone grab a copy they could post here?

Edit: got it OK now.

Fantastic news !

I hope NASA will now start taking the TPF serious, instead of cutting its funding

Mongo:


Now that's an impressive collaborative amateur effort. Nice.

Super-Earths (Jumbo Earths?) may well be the best places near red-dwarf stars. At a PURELY arm-waving hypothesis level, the greater escape velocity of a several-earth-mass planet will help offset potential atmosphere non-accretion and subsequent atmosphere loss/erosion mechanisms.

A relatively dense atmospere would also buffer temperature variations due to orbital eccentricity, and more efficiently carry heat from the dayside to the nightside of a tidally locked planet.

I have never seen press-release or published abstracts on modeling of atmosphere evolution on modestly larter-than-earth planets, particularly at lower-than-earth solar insolation levels... There may be a tipping point in terms of atmosphere mass where a snowball planet, only slightly warmed, could go into runaway greenhouse, for example, due to a greater-than-earths' column mass of atmosphere. The nonlinearities in such modeling put fissures in my brain's surface when I try to imagine the interrelations... (Oh.. those are SUPPOSED to be there.)

All.....


The research paper is here

http://exoplanet.eu/papers/udry_terre_HARPS-1.pdf

Glorious!!!

Craig

FWIW, a terrestrial planet with several times' Earth's mass might nonetheless concentrate more volatiles per unit surface area. Mass varies according to cube of radius, while surface area varies according to the square.

Imagine there's a planet with the same composition and temperature as Earth but twice the radius. It would have 8 times the mass (and thus 8 times the mass of volatiles as a planet of similar composition but 1 Earth mass), but only 4 times the surface area. Moreover, the scale height would be half as great, providing for 4 times the volatile "pressure" at the surface as a world of similar composition but Earth's size.

So, if the abundance of volatiles were just 10% that of Earth, the world would still end up with 40% of Earth's surface volatile density. That beats Mount Everest, anyway. Under lots of conditions, this world would end up with localized conditions that seem like cockroaches could cope if introduced.

Now the long wait for spectroscopy!!! Nitrogen and carbon dioxide seem like the best bets. H2O would make headlines. O2 would cause scientific delirium.

Classic quote from Natasha Kaplinsky, news presenter, on BBC News just now, humourously wrapping up the "new planet" story...

"So, liitle green men might be coming, but not for 20 light years..."

Jason and I have been discussing the weather patterns on the planet, and how they might be. We had some very interesting discussions. We assumed that the planet was tidally locked, and had some fairly large amount of water. We also assumed that the dark side of the planet was below freezing, and the bright side above. Depending on how much, one of the following could occur (Purely speculative).

1) If there wasn't a whole lot of water, it would likely freeze on the back side of the planet, the permanently shadowed region.
2) If there was on the order of 500m of water or so, there would likely be some kind of continents. These continents, if all moved to the dark side of the planet, could create an ice age that would cause all of the oceans to freeze. The bright side would still be fairly warm, but with almost no water.
3) If there was tons of water, then a cap might form on the dark side, but it would likely be pushed to the bright side. There may be polar caps.

This was just a what if conversation, but it sure was fun!

Hmm. Why would there be polar caps? Assuming no libration, it would seem any point on the terminator would be much like another.

--Greg

It pains me to say it, but there was a remarkably good two page spread in today's Daily Mail. Far better than the Guardian. I easily forgive '50 times cooler' in place of '50 times less luminous' and the rather sci-fi book cover illustration, which was anyway definitely eyecatching as intended. I don't know how they got such a good piece together so quickly. The name at the top is Michael Hanlon. It was also their front page lead, which is why I bought my very first Daily Mail.

Very fun speculation! Why do you figure the frozen cap would get pushed to the bright side?


On another note, how about the geology?

Anyone got a guess for whether this world could have plate tectonics? Given likely age, size, core heat flow, place of formation, and orbital eccentricity?

[I often wonder if plate tectonics initiates due to tidal forces just after the crust forms]

-Mike

It seems like another possibility is a dense atmosphere that moves enough heat around that the dark side is not that much cooler than the warm side. (Like Venus, but far "cold"er.) So let's say the global mean temp were 30 C with a difference of about 20 C between the subsolar point and the cold pole. That would be a nice Mediterranean climate worldwide. That would, I suppose, lead to almost all of the rain being on the night side, with rivers flowing towards the "light side" if topography did not forbid it. If there were seas, the sea levels would of course be in steady state on both hemispheres.

That's the "optimistic" outlook...

It could be extremely windy with giant storm waves on a global ocean. Oceanic circulation would help to moderate temperatures too. This is a wonderful place to let the imagination run wild!

Note that while the planet is almost certainly tidally despun, it MAY not be absolutely tidally locked.

The Moon is in a 1:1 tidal lock. Earthllings haven't seen the farside since (probably) the last basin forming impact.

Mercury is in a 3:2 tidal lock. It does exactly 3 rotations in 2 orbits.

Both are allowed to do real physical librations about their tidal lock, but they can't drift off lock. This is because their global gravitational field is elongated due to frozen-in irrugularities in mass distribution. They have global gravity anomalies.

A planet with plate (or other) tectonics, dense erosive atmosphere, and oceans may keep changing it's global gravitational "shape" sufficiently that it slowly re-orients around the syncyronous lock.

I've imagined a thin-atmosphere dwarf star planet that has a nightside ice-cap. But with dominantly east-west atmospheric circulation in a few weeks long orbit around the star (like Venus or Titan), you might have moisture deposited on one edge of the nightside and dry winds blowing off the other. The ice-cap might gradually creep it's way around the planet, or more accurately, the planet might very slowly rotate under the tidally locked nightside ice cap!

Expect the non-linear. Expect the bizarre. Expect the unexpectible (except by wild-ass-guess!).

Yeah, if the planet formed in-situ, it probably is dry. But if it migrated from beyond the ice line most of the planet could be icy. The latter seems more plausible, given that the planet b, the most massive planet in the system orbits inside the planet c.

I'm really proud to see the "old" Observatório Astronómico de Lisboa envolved in such a discovery...
Now, seriously, what's the best trajectory to get there?

The frozen cap would get pushed to the bright side if there was a global ocean due to currents, there would almost certainly have to be some kind of a current.

Okay, Jason and I discussed plate tectonics as well. Essentially we agreed that there would be some kind of tectonics, but likely the planet would be very smooth, something like Venus. With a gravitational field stronger than Earth's, it would probably not be enough to form continents, unless there was on the order of maybe 1km total surface coverage of water.

Plate tectonics develop due to a difference in heat from the inside of the planet to the outside. It is further enhanced by oceans. I don't know why Venus doesn't have plate tectonics that we know of (Or maybe it does and I'm just ignorant), but that's the leading cause as to why they exist (At least, as I understand from my 1 geology class I've ever taken...)

We talked a bit about eccentricity, but it's hard to say. Most likely there would be some kind of affect of the closer planet, changing it's orientation somewhat, but how is hard to say. It sure would be a wacky star system, no doubt about it.

If it is tidally-locked, I'd expect it to be a pretty quiet place in terms of weather. Heat transfer from the sub-solar point to the anti-solar point and back via winds, but with those points not moving, I'd expect it to be in a pretty stable equilibrium. Sidereal period of 13 days doesn't seem like enough to have much influence.

Sub-solar point probably has a permanent storm as the rising air sheds water. Especially if it's over the ocean, but even if it's not -- unless there's very little water at all.

At the anti-solar point, I'd expect strong, katabatic winds (if you can call them that, when the "slope" is straight down), but they'd be very dry. I'd expect you to have something like Antarctica there, with lots of ice despite very, very little precipitation. In this case, I think you'd have a giant pile of ice even if it's in the middle of the ocean, but I'm just guessing.

But it does seem reasonable that there would be an equilibrium with water on the day side too. First, that dry wind would sublime at least some of the ice and carry it back to the day side. Second, any ocean that straddled the terminator would have similar current flows, transporting far more heat. With the warm water on the surface and the dry wind blowing from dark to light, the whole system would seem to have powerful forces moving water back to the day side.

I gather it's way too early for anyone to have run any kind of serious simulation.

--Greg

It seems to me that at least in case 1) and 2) You would have a sort of Half-Snowball-Earth situation. If all or nearly all the water freezes on the night side weathering comes nearly to a stop and there are no oceans to absorb CO2, but volcanoes keep adding CO2 to the atmosphere until it becomes warm enough for the ice to start melting. I would expect an equilibrum situation where there is just enough liquid water for weathering plus carbonate production to absorb the CO2 created by volcanism.
It might still be pretty dry and it might be VERY hot near the subsolar point though.

I don't think it would be half-snowball Earth. Keep in mind that there is global wind and water circulation. It would be a very interesting pattern though, actually, it's probably quite a bit different than I had first thought of. Likely there would be 5 stripes, that each go about half-way through, alternating which end of the globe they start on, due to trade winds and such. And I also don't think it would snow right at the terminator, only further down... The result would be very interesting, that much I would imagine...

Would the world be super-flexy like Io and have lava oozing out all over the place?

(I'm guessing Jason was rooting for this possibility?)

With more mass, but lower metallicity from the initial nebula, would that mean that the core would be proportionaly smaller than Earth's?

Would the crust be thicker than Earths (more lighter weight stuff)?

But shouldn't there still be enough radionucleides and overall mass that the planet would take a really loooong time to cool?


I would speculate that either way, the planet would be tectonically active and belching out nice greenhouse gases. (If there is enough water to lube the plates).

I'd [wildly] speculate that the planet may look more like a big Venus with oceans (with a smoother topology like Ganymede). (And a smaller ice cap on the antisolar point). The relative amounts of lighter/darker basaltics would determine whether or not there were continents and basins.

-Mike

So when we finally get a "magic pixel" (from TPS or whatever) and can try to guess what is going on:

Assuming it is tidally locked:
A regular brightness variation during it's orbit would imply either continents and oceans or a very regular weather pattern (seasonal? - would need to be able to explain season based on eccentricity).


-Mike