2 interesting recent discoveries

[Snarknado]

https://phys.org/news/2019-05-formation-moon-brought-earth.html

presents evidence that the impact that led to formation of the Moon was also the source of Earth's water,

and

https://www.sciencedaily.com/releases/2019/03/190318121055.htm

about the discovery of a binary star formation; though most binaries are still thought to be a "capture" of a separately-formed star in a nearby cluster, this shows that a large accretion disk can spawn a smaller orbiting star which can then steal enough matter from the outer disk to rival the main star in size. This pair is 1 light-day apart, allowing a radio telescope array to penetrate the dust and resolve the separate objects.

Interesting stuff...

[sneakypete]

https://phys.org/news/2019-05-formation-moon-brought-earth.html

presents evidence that the impact that led to formation of the Moon was also the source of Earth's water,

and

https://www.sciencedaily.com/releases/2019/03/190318121055.htm

about the discovery of a binary star formation; though most binaries are still thought to be a "capture" of a separately-formed star in a nearby cluster, this shows that a large accretion disk can spawn a smaller orbiting star which can then steal enough matter from the outer disk to rival the main star in size. This pair is 1 light-day apart, allowing a radio telescope array to penetrate the dust and resolve the separate objects.

Interesting stuff...

@Snarknado

Yes,it is interesting stuff.

Thank you for posting it.

[bigheadfred]

bkmk

[kidd]

https://phys.org/news/2019-05-formation-moon-brought-earth.html

presents evidence that the impact that led to formation of the Moon was also the source of Earth's water,

These are both good articles.
But just taking this one to a next step...

The article notes that the inner planets are dry, so it is really unusual that Earth has so much water.
It theorizes that Earth's water came from a Mars sized planet that originated from the outer solar system and collided with Earth.

Seems to me that this provides significant support for the "rare Earth" hypothesis...that life in the Milky Way galaxy is very rare.

OTOH - it doesn't explain the observations that Mars itself once had lakes and flowing water. Where did the ancient water on Mars come from?

[sneakypete]

@sneakypete

Self-ping for when I have more time.

[Snarknado]

These are both good articles.
But just taking this one to a next step...

The article notes that the inner planets are dry, so it is really unusual that Earth has so much water.
It theorizes that Earth's water came from a Mars sized planet that originated from the outer solar system and collided with Earth.

Seems to me that this provides significant support for the "rare Earth" hypothesis...that life in the Milky Way galaxy is very rare.

OTOH - it doesn't explain the observations that Mars itself once had lakes and flowing water. Where did the ancient water on Mars come from?

This earlier article from 2014 argues that Earth formed with water :
https://www.nationalgeographic.com/news/2014/10/141030-starstruck-earth-water-origin-vesta-science/

What's new in the more recent research is the correlation of molybdenum isotope composition in the Earth's mantle with objects that formed in the outer solar system. A Mars-sized object from that region could have contained a huge amount of ice.

The other theory was that icy comet impacts delivered all of Earth's water after it had cooled somewhat - that always seemed like a stretch to me. It might reasonably account for smaller quantities on Mars, especially considering that Mars would have cooled much faster than Earth.

I've always leaned toward the rare Earth hypothesis. Interestingly (to me at least) Asimov's Foundation depicted a galaxy inhabited only by humans, with the small inner planet/large moon being unique in the galaxy.

However the water got here, the impact resulting in a large, close-in moon would have produced super tides, churning mixtures with other elements and compounds, possibly a major factor in the development of life.

[sneakypete]

OTOH - it doesn't explain the observations that Mars itself once had lakes and flowing water. Where did the ancient water on Mars come from?

@kidd

I think the thing I love the most about science is the fact that every answer science supplies to us seems to also furnish us with even more questions.

How boring would life be if we knew all the answers?

Or even understood all the questions?

[Snarknado]

More on rare earth hypothesis - I'm watching the Planets series on Nova, mostly so-so, Quinto's narration is mediocre, but the episode on Jupiter is pretty interesting. The theory is that Jupiter was the only planet fully formed when the sun ignited. The accretion disk was still thick, slowing its orbit so it spiraled inward and stole a lot of material from the inner disk, harshly disrupting the formation of Mars and the asteroid belt region. That thinning prevented formation of a "super earth" seen in other star systems. Fortunately, Saturn formed in time to also spiral inward and establish orbital resonance with Jupiter to cause both to return to their present orbits. The result is a solar system very different from the others we've discovered.

[Absalom]

Interesting, perhaps, but of no interest; rather a query.
The purpose of Science is to expand human knowledge, the objective being to better his condition.
As such, which discoveries had the greatest impact on that objective?
1.) Euclid's creation of Geometry?
2.) Newton's discovery of the Laws of Motion?
or
3.) Darwin's Theory of Evolution?
4.) Einsteins Theory of Relativity?

[Smokin Joe]

These are both good articles.
But just taking this one to a next step...

The article notes that the inner planets are dry, so it is really unusual that Earth has so much water.
It theorizes that Earth's water came from a Mars sized planet that originated from the outer solar system and collided with Earth.

Seems to me that this provides significant support for the "rare Earth" hypothesis...that life in the Milky Way galaxy is very rare.

OTOH - it doesn't explain the observations that Mars itself once had lakes and flowing water. Where did the ancient water on Mars come from?

Maybe the pertinent question about Mars, is Where did it go? (and Why didn't that happen to Earth?)

Maybe those lakes and flowing streams were not H2O.

[Snarknado]

Maybe the pertinent question about Mars, is Where did it go? (and Why didn't that happen to Earth?)

Maybe those lakes and flowing streams were not H2O.

I think it's generally accepted that Mars was too small to retain heat for as long as Earth - the molten core cooled and solidified, killing its magnetic field, and solar wind then stripped most of the atmosphere. Any liquid water in effect just evaporated into space.

[InHeavenThereIsNoBeer]

Maybe the pertinent question about Mars, is Where did it go? (and Why didn't that happen to Earth?)

Maybe those lakes and flowing streams were not H2O.

IIRC, the prevailing theory is that Mars lost its water and atmosphere to the solar wind after it lost its magnetic field.

It hasn't happened to Earth because we were smart enough to ban CFCs.  And DDT.  And CNN.

[Smokin Joe]

IIRC, the prevailing theory is that Mars lost its water and atmosphere to the solar wind after it lost its magnetic field.

It hasn't happened to Earth because we were smart enough to ban CFCs.  And DDT.  And CNN.

Well, two out of three ain't bad, as Meatloaf sang, but, imho they got the wrong ones.

[InHeavenThereIsNoBeer]

Maybe the pertinent question about Mars, is Where did it go? (and Why didn't that happen to Earth?)

Maybe those lakes and flowing streams were not H2O.

Watched a show about Mars on the DVR last night that said that Mars, being smaller than the Earth, cooled sooner.  So maybe the same thing simply hasn't happened to Earth yet.

[Smokin Joe]

Watched a show about Mars on the DVR last night that said that Mars, being smaller than the Earth, cooled sooner.  So maybe the same thing simply hasn't happened to Earth yet.

Maybe, but Earth has a moon to exert significant tidal forces. These affect not only the oceans, but even the fluid in oil reservoirs, and the planet's liquid core. It's safe to say that has some effect on the planet. Whether Mars had some sort of liquid core, (you'd think there would be some remnant magnetism), is hard to say, but it didn't exert the same effects, possibly related to the absence of a moon of significant ehough mass.
The magnetic field not only orients critters (migratory and other navigation), but produces field effects which shield the planet from ionizing radiation (Van Allen Belts).
A hot core (likely nuclear decay ) keeps the middle layers in flux, shunting the surface features around (plate tectonics), and affecting the planet surface as well as atmosphere and weather/climate. 

There are a lot of wonderful and relatively (within the scope of our knowledge at this point) unique features of this planet that contribute to it being habitable.

[InHeavenThereIsNoBeer]

Maybe, but Earth has a moon to exert significant tidal forces. These affect not only the oceans, but even the fluid in oil reservoirs, and the planet's liquid core. It's safe to say that has some effect on the planet. Whether Mars had some sort of liquid core, (you'd think there would be some remnant magnetism), is hard to say, but it didn't exert the same effects, possibly related to the absence of a moon of significant ehough mass.
The magnetic field not only orients critters (migratory and other navigation), but produces field effects which shield the planet from ionizing radiation (Van Allen Belts).
A hot core (likely nuclear decay ) keeps the middle layers in flux, shunting the surface features around (plate tectonics), and affecting the planet surface as well as atmosphere and weather/climate. 

There are a lot of wonderful and relatively (within the scope of our knowledge at this point) unique features of this planet that contribute to it being habitable.

Sorry, I was a bit terse.   The idea was that Mars had a liquid core, which contributed to generating a magnetic field.  When the planet cooled and the core solidified the field was lost and (surface) water was stripped away with the atmosphere.

[Smokin Joe]

Sorry, I was a bit terse.   The idea was that Mars had a liquid core, which contributed to generating a magnetic field.  When the planet cooled and the core solidified the field was lost and (surface) water was stripped away with the atmosphere.

There are features on the surface there which indicate water may have been (and may still be) frozen in the subsurface, where the heat from impacts thawed the water resulting in brief, but catastrophic erosion. So there may still be water there, just not in liquid form, and locked in sediment. Not much for life (as we know it) to go on.

Does Mars still have a magnetic field? Even solid iron exerts some force in that regard.
Because of the lower planetary mass, I would expect less Iron in the core, and a lower effect than Earth's, but there is a smaller planetary radius as well so surface effects of the same level of magnetism would be greater for a given field strength than they would be on a larger planet's surface.

[Snarknado]

The core has to be liquid conductive material so the planet's rotation relative to the core can produce the electromagnetic field. Once the core solidifies the planet rotates as a rigid body. The iron itself would still be magnetic but only a small fraction of the electromagnetic strength.

Jupiter doesn't have an iron core but it's immense gravity compresses and ionizes the gases in its core. The huge amount of freely flowing conductive material plus rapid rotation produce its powerful magnetic field.

Venus has an iron core but no magnetic field, maybe due to extremely slow rotation.