RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Find out the latest thinking about our universe.
User avatar
bystander
Apathetic Retiree
Posts: 15954
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby bystander » Thu Apr 20, 2017 4:55 pm

Oceans Galore: Most Habitable Planets May Lack Dry Land
Royal Astronomical Society | 2017 Apr 20

waterworld_earth.jpg

When it comes to exploring exoplanets, it may be wise to take a snorkel along. A new study, published in a paper in the journal Monthly Notices of the Royal Astronomical Society, has used a statistical model to predict that most habitable planets may be dominated by oceans spanning over 90% of their surface area.

The author of the study, Dr. Fergus Simpson of the Institute of Cosmos Sciences at the University of Barcelona, has constructed a statistical model -- based on Bayesian probability -- to predict the division between land and water on habitable exoplanets.

For a planetary surface to boast extensive areas of both land and water, a delicate balance must be struck between the volume of water it retains over time, and how much space it has to store it in its oceanic basins. Both of these quantities may vary substantially across the full spectrum of water-bearing worlds, and why the Earth’s values are so well balanced is an unresolved and long-standing conundrum.

Simpson’s model predicts that most habitable planets are dominated by oceans spanning over 90% of their surface area. This conclusion is reached because the Earth itself is very close to being a so-called ‘waterworld’ -- a world where all land is immersed under a single ocean. ...

The Earth Has Oceans And Continents: How Weird Is That?
National Public Radio (NPR) | 2017 Mar 07

Bayesian Evidence for the Prevalence of Waterworlds - Fergus Simpson
You do not have the required permissions to view the files attached to this post.
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

BDanielMayfield
Don't bring me down
Posts: 1348
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: South Texas

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby BDanielMayfield » Thu Apr 20, 2017 6:01 pm

Man, would I love to quote Genesis chapter 1 verses 2 and 9 here.

Anyway, the notion of Earth as a water world has a long tradition.

Bruce
"Happy are the peaceable ... "

User avatar
Ann
4725 Å
Posts: 8307
Joined: Sat May 29, 2010 5:33 am

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby Ann » Thu Apr 20, 2017 10:20 pm

All the water on the Earth.
Credit: Howard Perlman, USGS; globe illustration by Jack Cook,
Woods Hole Oceanographic Institution (©); Adam Nieman.
The Earth doesn't really have a lot of water at all. It just keeps its water where life needs it: At the interfaces.

The crucial interfaces are the interface between the Earth and its atmosphere, and the interfaces between dry land and bodies of liquid water, and the interfaces between solid ice and liquid water.

Most life in the oceans is found in the shallow parts of the oceans, not far from dry land. And most life on dry land on the Earth, I'm sure, is found along the coasts of continents and along coastlines of lakes and rivers.

Ann
Color Commentator

BDanielMayfield
Don't bring me down
Posts: 1348
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: South Texas

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby BDanielMayfield » Fri Apr 21, 2017 12:33 am

Ann wrote:The Earth doesn't really have a lot of water at all.


As compared to the total volume of Earth's rocks, sure. But, as potential water worlds are concerned, it is note worthy that if the rocky surface of this planet was completely spherical water would cover the whole planet to a depth of about 2.5 km.

As far as exoplanets in the liquid water zones are concerned, the amount of solid surface relief will be a very important factor as to whether or not any dry land will exist. A relatively small amount of water can go a long way if the solid surface has very little relief. Low relief should be common on higher G Super Earths. Also, here we have land because we have plate tectonics and volcanism. Without the constant reworking by these processes the land would eventually be worn down to sea level by erosion. Therefore the conclusion of this paper, "Most Habitable Planets May Lack Dry Land" probably isn't all wet. :wink:

Bruce
"Happy are the peaceable ... "

User avatar
Ann
4725 Å
Posts: 8307
Joined: Sat May 29, 2010 5:33 am

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby Ann » Fri Apr 21, 2017 6:35 pm

Perhaps unlike Bruce (but perhaps not unlike Bruce :wink: ), I am so often amazed by the Earth's remarkable properties. The fact that the Earth has both plenty of liquid oceans at its surface as well as a lot of dry land is one of those remarkable properties.

Peter D Ward and Donald Brownlee wrote in their book Rare Earth:

Had Earth formed from materials similar to those in the asteroid belt, farther from the Sun, its ocean could have been hundreds of kilometers deep, and its carbon content would have been higher by many orders of magnitude. Both of these aspects would have resulted in a planet totally covered by water and with vast amounts of CO2 in its atmosphere. The resulting greenhouse heating would have produced Venus-like surface temperatures...
...
The violent events of these times may have determined the final abundance of water and carbon dioxide, two compounds that play crucial roles in the ability of Earth to maintain an environment where life can survive. It is interesting to speculate about what would have happened if the final abundance of these had varied. If Earth had had just a little more water, continents would not extend beyond sea level. Had there been more CO2, Earth would probably have remained too hot to host life, much like Venus.
...
In the case of our planet, Earth managed to form continents that could endure for billions of years. That required the formation of land masses made of relatively low-density materials that could permanently "float" on the denser underlying mantle while parts of them extended above the sea.
...
In any event, the outcome was a planet with both land and sea. This fortuitous combination may be the most important factor that ultimately made life possible.


Ann
Color Commentator

warmingwarmingwarming
Science Officer
Posts: 110
Joined: Sat Apr 22, 2017 1:19 am

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby warmingwarmingwarming » Fri Apr 21, 2017 9:40 pm

BDanielMayfield wrote:
Ann wrote:The Earth doesn't really have a lot of water at all.


As compared to the total volume of Earth's rocks, sure. But, as potential water worlds are concerned, it is note worthy that if the rocky surface of this planet was completely spherical water would cover the whole planet to a depth of about 2.5 km.

As far as exoplanets in the liquid water zones are concerned, the amount of solid surface relief will be a very important factor as to whether or not any dry land will exist. A relatively small amount of water can go a long way if the solid surface has very little relief. Low relief should be common on higher G Super Earths. Also, here we have land because we have plate tectonics and volcanism. Without the constant reworking by these processes the land would eventually be worn down to sea level by erosion. Therefore the conclusion of this paper, "Most Habitable Planets May Lack Dry Land" probably isn't all wet. :wink:

Bruce


Your reference to the Genesis account of earth's creation was daring, Daniel, and your revelation that without high elevations of mountains etc all of earth's dry land would be deep under water was refreshing.

And then there is the vast known and unknown reserves of water beneath and inside of earth's land masses, a mere two of which vastly changes the graphic comparison of a ball of water to the entire planet.

http://www.bing.com/search?q=ocean+beneath+china&src=IE-TopResult&FORM=IETR02&conversationid=
https://www.theguardian.com/environment/2011/aug/26/underground-river-amazon

BDanielMayfield
Don't bring me down
Posts: 1348
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: South Texas

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby BDanielMayfield » Fri Apr 21, 2017 11:07 pm

Rare Earth is in my personal library. I thought it's conclusions were resonable, but the authors have caught some flack over it, I think due to wishful assumptions of many that truely Earth-like planets are common. I had the same wishes myself, so although the book's logic was sound I didn't really want it to be true.

But the diversity of planets is probably huge. Now that we know that planets are extremely common we'll probably find all kinds of hydro and chemical combinations. Planets like CO2 choked Venus, dried out Mars, and totally flooded water worlds could all prove to be far more common than true Earth twins.

But hey thar ye mateys, if complex life is common, (contrary to the Rare Earth Model), then with the galaxy awash in water worlds, then thar could be whales, giant squid, octopi, megaladons, and all manner of assorted "great sea monsters" (Gen 1:21) in dem dar humongous oceans out there :!:

Bruce

User avatar
rstevenson
Quis custodiet ipsos custodes?
Posts: 2396
Joined: Fri Mar 28, 2008 1:24 pm
Location: Dartmouth, NS, Canada

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby rstevenson » Fri Apr 21, 2017 11:23 pm

BDanielMayfield wrote:... if complex life is common, (contrary to the Rare Earth Model), then with the galaxy awash in water worlds, then thar could be whales, giant squid, octopi, megaladons, and all manner of assorted "great sea monsters" (Gen 1:21) in dem dar humongous oceans out there :!:

Bruce

And some of them might be arguing over the remote possibility that simians, clever mimics though they are, could ever acheive true intelligence.

Rob

BDanielMayfield
Don't bring me down
Posts: 1348
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: South Texas

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby BDanielMayfield » Fri Apr 21, 2017 11:47 pm

WarmingWarmingWarming wrote:Your reference to the Genesis account of earth's creation was daring, Daniel, and your revelation that without high elevations of mountains etc all of earth's dry land would be deep under water was refreshing.

But I don't wish to make too many waves here Warming3, and don't want to heat up the watery deep too much. :wink:

And then there is the vast known and unknown reserves of water beneath and inside of earth's land masses, a mere two of which vastly changes the graphic comparison of a ball of water to the entire planet.

I doubt that the amount of water inside the Earth's rocky surface currently rivals the volume of the current world ocean. However, it is interesting that most of the Earth's water is now believed by many to have come from the planet's early formation, and thus it may have come up to the surface via volcanos, hot springs, etc.

Bruce, my scientific side
"Happy are the peaceable ... "

warmingwarmingwarming
Science Officer
Posts: 110
Joined: Sat Apr 22, 2017 1:19 am

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby warmingwarmingwarming » Sat Apr 22, 2017 1:28 am

BDanielMayfield wrote:
WarmingWarmingWarming wrote:Your reference to the Genesis account of earth's creation was daring, Daniel, and your revelation that without high elevations of mountains etc all of earth's dry land would be deep under water was refreshing.

But I don't wish to make too many waves here Warming3, and don't want to heat up the watery deep too much. :wink:


I doubt that the amount of water inside the Earth's rocky surface currently rivals the volume of the current world ocean. However, it is interesting that most of the Earth's water is now believed by many to have come from the planet's early formation, and thus it may have come up to the surface via volcanos, hot springs, etc.


Bruce, my scientific side


Until VERY recently it was considered fact that Mars lacked water, and that Pluto was a frozen solid rock incapable of carrying liquid. Technological advancement is now so fast we barely begin sipping new information before were deluged by tsunamis of data. We never should have assumed we knew what we knew .. moreso now in this age of quantum leaps in knowledge.

warmingwarmingwarming
Science Officer
Posts: 110
Joined: Sat Apr 22, 2017 1:19 am

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby warmingwarmingwarming » Sat Apr 22, 2017 1:31 am

Moderator please note I changed my sign in to warmingwarmingwarming3 for the above post only because I registered as warmingwarmingwarming after my first post .. then found that ID was not allowed .. oh .. I see .. I have to sign in to use it. Beginners bad luck I suppose.

warmingwarmingwarming
Science Officer
Posts: 110
Joined: Sat Apr 22, 2017 1:19 am

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby warmingwarmingwarming » Sat Apr 22, 2017 1:32 am

warmingwarmingwarming3 wrote:Moderator please note I changed my sign in to warmingwarmingwarming3 for the above post only because I registered as warmingwarmingwarming after my first post .. then found that ID was not allowed .. oh .. I see .. I have to sign in to use it. Beginners bad luck I suppose.


Have I fixed my error? I shall know only when I push the 'Submit.'

Aha .. success .. and with success comes editorship.

User avatar
Ann
4725 Å
Posts: 8307
Joined: Sat May 29, 2010 5:33 am

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby Ann » Sat Apr 22, 2017 3:01 am

WarmingWarmingWarming wrote:
And then there is the vast known and unknown reserves of water beneath and inside of earth's land masses, a mere two of which vastly changes the graphic comparison of a ball of water to the entire planet.

http://www.bing.com/search?q=ocean+beneath+china&src=IE-TopResult&FORM=IETR02&conversationid=
https://www.theguardian.com/environment/2011/aug/26/underground-river-amazon


We have currently no reason to believe that there is much water inside the Earth at all. There may well be pockets of water relatively close to the surface that have remained undiscovered until now, but they are certainly insignificant compared to the total known volume of the oceans.

We have every reason to think that the Earth has little underground water. These are the main reasons:

1) Almost certainly, planet Earth formed on the warm side of the "snow line" of the protoplanetary disk of the early solar system. On the warm side of the snow line, H2O was gaseous and could not be swept up by the rocky bodies forming there. On the cold side of the snowline, H2O was frozen solid and could be swept up and incorporated in large amounts into the planets and moons forming there. That is why Neptune and Uranus and the Jovian and Saturnian moons are so ice-rich, and that is why the inner planets, including the Earth's Moon, are so dry. It is believed that planet Earth would not have had much water at all, if water hadn't been delivered here early in our planet's history by ice-rich asteroids crashing onto the Earth.

2) Water has a very low density, but the Earth is the most dense planet of the solar system. If the Earth contained large amounts of hidden underground water, it wouldn't be nearly so dense.

Even though we have good reasons to think that there are undiscovered pockets of water in the upper mantle of the Earth, we have no reasons to think that the volume of water that these underground pockets contain can in any way rival the amounts of water that are already known to exist in the Earth's oceans.

Ann
Color Commentator

BDanielMayfield
Don't bring me down
Posts: 1348
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: South Texas

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby BDanielMayfield » Sat Apr 22, 2017 12:32 pm

Ann wrote:
WarmingWarmingWarming wrote:
And then there is the vast known and unknown reserves of water beneath and inside of earth's land masses, a mere two of which vastly changes the graphic comparison of a ball of water to the entire planet.

http://www.bing.com/search?q=ocean+beneath+china&src=IE-TopResult&FORM=IETR02&conversationid=
https://www.theguardian.com/environment/2011/aug/26/underground-river-amazon


We have currently no reason to believe that there is much water inside the Earth at all. There may well be pockets of water relatively close to the surface that have remained undiscovered until now, but they are certainly insignificant compared to the total known volume of the oceans.

We have every reason to think that the Earth has little underground water. These are the main reasons:

1) Almost certainly, planet Earth formed on the warm side of the "snow line" of the protoplanetary disk of the early solar system. On the warm side of the snow line, H2O was gaseous and could not be swept up by the rocky bodies forming there. On the cold side of the snowline, H2O was frozen solid and could be swept up and incorporated in large amounts into the planets and moons forming there. That is why Neptune and Uranus and the Jovian and Saturnian moons are so ice-rich, and that is why the inner planets, including the Earth's Moon, are so dry. It is believed that planet Earth would not have had much water at all, if water hadn't been delivered here early in our planet's history by ice-rich asteroids crashing onto the Earth.

2) Water has a very low density, but the Earth is the most dense planet of the solar system. If the Earth contained large amounts of hidden underground water, it wouldn't be nearly so dense.

Even though we have good reasons to think that there are undiscovered pockets of water in the upper mantle of the Earth, we have no reasons to think that the volume of water that these underground pockets contain can in any way rival the amounts of water that are already known to exist in the Earth's oceans.

Ann


I agree with this Ann. The only adjustment I would make is that the original rocks that built up to form the Earth may have contained some water in the form of hydrated minerals even inside the snow line. Heat and pressure would have driven much of this water toward the surface over time.

Bruce
"Happy are the peaceable ... "

User avatar
Chris Peterson
Abominable Snowman
Posts: 13040
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby Chris Peterson » Sat Apr 22, 2017 1:57 pm

Ann wrote:We have currently no reason to believe that there is much water inside the Earth at all. There may well be pockets of water relatively close to the surface that have remained undiscovered until now, but they are certainly insignificant compared to the total known volume of the oceans.

This is not true. In fact, recent research argues that there could be 2-3 times more water in the mantle than all the surface water. This water is bound to minerals, so it doesn't resemble some sort of underground lakes, but it plays a profound role in tectonics and mantle dynamics, and is probably part of a long term water cycle where it gets returned to the surface, and surface water is subducted into the mantle.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
Ann
4725 Å
Posts: 8307
Joined: Sat May 29, 2010 5:33 am

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby Ann » Sat Apr 22, 2017 3:24 pm

Chris Peterson wrote:
Ann wrote:We have currently no reason to believe that there is much water inside the Earth at all. There may well be pockets of water relatively close to the surface that have remained undiscovered until now, but they are certainly insignificant compared to the total known volume of the oceans.

This is not true. In fact, recent research argues that there could be 2-3 times more water in the mantle than all the surface water. This water is bound to minerals, so it doesn't resemble some sort of underground lakes, but it plays a profound role in tectonics and mantle dynamics, and is probably part of a long term water cycle where it gets returned to the surface, and surface water is subducted into the mantle.


Sounds reasonable. Point taken.

And the lack of plate tectonics on Mars may have many reasons, but might we guess that it has something to do with a relative dearth of underground water?

Ann
Color Commentator

BDanielMayfield
Don't bring me down
Posts: 1348
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: South Texas

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby BDanielMayfield » Sat Apr 22, 2017 6:32 pm

Chris Peterson wrote:
Ann wrote:We have currently no reason to believe that there is much water inside the Earth at all. There may well be pockets of water relatively close to the surface that have remained undiscovered until now, but they are certainly insignificant compared to the total known volume of the oceans.

This is not true. In fact, recent research argues that there could be 2-3 times more water in the mantle than all the surface water. This water is bound to minerals, so it doesn't resemble some sort of underground lakes, but it plays a profound role in tectonics and mantle dynamics, and is probably part of a long term water cycle where it gets returned to the surface, and surface water is subducted into the mantle.


Wow, very interesting. Thanks for adding this insight.
"Happy are the peaceable ... "

warmingwarmingwarming
Science Officer
Posts: 110
Joined: Sat Apr 22, 2017 1:19 am

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby warmingwarmingwarming » Tue Apr 25, 2017 9:39 pm

Ann wrote:
Sounds reasonable. Point taken.

And the lack of plate tectonics on Mars may have many reasons, but might we guess that it has something to do with a relative dearth of underground water?

Ann


Ann, this may interest you .. there is no lack of plate tectonics on Mars. http://newsroom.ucla.edu/releases/ucla-scientist-discovers-plate-237303

Also this, that Mars may have as much underground water as earth. http://io9.gizmodo.com/5920536/whoa-mars-might-have-as-much-water-underground-as-earth-does

User avatar
Ann
4725 Å
Posts: 8307
Joined: Sat May 29, 2010 5:33 am

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby Ann » Wed Apr 26, 2017 4:35 am

warmingwarmingwarming wrote:
Ann wrote:
Sounds reasonable. Point taken.

And the lack of plate tectonics on Mars may have many reasons, but might we guess that it has something to do with a relative dearth of underground water?

Ann


Ann, this may interest you .. there is no lack of plate tectonics on Mars. http://newsroom.ucla.edu/releases/ucla-scientist-discovers-plate-237303

Also this, that Mars may have as much underground water as earth. http://io9.gizmodo.com/5920536/whoa-mars-might-have-as-much-water-underground-as-earth-does


I apologize for bringing up Mars in relation to plate tectonics when there was no reason for it.

However, now that the cat is out of the bag, let's see what Wikipedia says about plate tectonics and Mars:

Wikipedia wrote:

Mars is considerably smaller than Earth and Venus, and there is evidence for ice on its surface and in its crust. In the 1990s, it was proposed that Martian Crustal Dichotomy was created by plate tectonic processes.[73] Scientists today disagree, and think that it was created either by upwelling within the Martian mantle that thickened the crust of the Southern Highlands and formed Tharsis[74] or by a giant impact that excavated the Northern Lowlands.[75]

Valles Marineris may be a tectonic boundary.[76]

Observations made of the magnetic field of Mars by the Mars Global Surveyor spacecraft in 1999 showed patterns of magnetic striping discovered on this planet. Some scientists interpreted these as requiring plate tectonic processes, such as seafloor spreading.[77] However, their data fail a "magnetic reversal test", which is used to see if they were formed by flipping polarities of a global magnetic field.


The verdict seems to be that there is some evidence for plate tectonics on Mars.

And there are, of course, large quantities of underground water on Mars. However, there appears to be no water on Venus, and Venus seems to lack plate tectonics:

Wikipedia wrote:

Venus shows no evidence of active plate tectonics.
...
One explanation for Venus's lack of plate tectonics is that on Venus temperatures are too high for significant water to be present.[71][72] The Earth's crust is soaked with water, and water plays an important role in the development of shear zones. Plate tectonics requires weak surfaces in the crust along which crustal slices can move, and it may well be that such weakening never took place on Venus because of the absence of water. However, some researchers[who?] remain convinced that plate tectonics is or was once active on this planet.


Ann
Last edited by Ann on Thu Apr 27, 2017 1:44 am, edited 1 time in total.
Color Commentator

warmingwarmingwarming
Science Officer
Posts: 110
Joined: Sat Apr 22, 2017 1:19 am

Re: RAS: Oceans Galore: Most Habitable Planets May Lack Dry Land

Postby warmingwarmingwarming » Wed Apr 26, 2017 11:53 pm

Ann wrote:
Wikipedia wrote:

Venus shows no evidence of active plate tectonics.
...
One explanation for Venus's lack of plate tectonics is that on Venus temperatures are too high for significant water to be present.[71][72] The Earth's crust is soaked with water, and water plays an important role in the development of shear zones. Plate tectonics requires weak surfaces in the crust along which crustal slices can move, and it may well be that such weakening never took place on Venus because of the absence of water. However, some researchers[who?] remain convinced that plate tectonics is or was once active on this planet.


Absolutely no water on the surface, no question, Ann, though there is a miniscule amount in the atmosphere .. .0002% https://www.universetoday.com/36291/is-there-water-on-venus/

But ... this offers a hint that there MAY be water in the interior .. for it seems the heating of the exterior may have cooled the interior.

http://www.astrobio.net/venus/venus-hot-outside-cool-inside/
I think I think, though I'm not sure if I all the thoughts I think I think, or if they come to me from .. goodness knows where. :)


Return to “The Communications Center: Breaking Science News”

Who is online

Users browsing this forum: CommonCrawl [Bot] and 0 guests