This is where Curiosity's been sitting the last couple weeks - confirming the obvious.

http://www.jpl.nasa.gov/news/news.php?feature=4734

Our challenge is to figure out how this more clement Mars was even possible, and what happened to that wetter Mars

Indeed. I'd like to know.

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The mind is a weird and mysterious place

Mars is too small and therefore had insufficient gravity to hold its atmosphere and water. Its water literally evaporated into space.

This is another parameter that is required for the existence of a truly Earth-Like planet. In other words Mars is not "habitable" in the sense that Earth is.

We have not yet found a habitable planet; that explains why we have not yet found ET. Have have we even listed the parameters required and their ranges of values that are required for a truly "Habitable" planet?

Mars is not habitable due to:
Temperature
Atmosphere
Potable water
Cosmic rays

Now what is needed on an exo-planet to not have these disqualifiers?

Yes it might be possible to go to Mars and live inside an enclosed compound--but primitive life could not erect such a structure and therefore such a planet would not house ET.

Mars is too small and therefore had insufficient gravity to hold its atmosphere and water. Its water literally evaporated into space.

But how was it possible in the first place, and why did it take so long to go (mostly) away?

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The mind is a weird and mysterious place

While we probably don't know for sure: The process which brought water to our world---perhaps by comets or small proto-planets ---also occurred on Mars.

On Mars there was insufficient atmospheric pressure to keep the water from very slowly effervescing and drifting off into space.

Various searches have indicated that a lot of water may be trapped in the subsurface or in the polar regions and appears to grow and shrink with the seasons--these speculations are still debated however. Ice may go directly to gaseous form due to the pressure/temperature conditions there on Mars.

It appears that most of the problems for life on Mars, such as low temperatures, availability of potable water at the surface, and solar and cosmic radiation could all be helped if there were a substantial atmosphere.
Mars' atmosphere is believed to have been eroded from the top, by energetic solar particles that impacted molecules of gases and sent they flying away from the planet. A very slow process, to be sure, but it eventually created the conditions we see today.
There is known to be a good deal of water, locked up in Mars' polar caps. It's been estimated that if melted under circumstances that would allow standing water, these would cover the entire surface of the planet to a depth of about 18 feet. Besides the polar caps we have direct evidence of ice in the bottoms of shaded craters, and firm indications of at least one very substantial slab of ice beneath the surface.

Mars is too small and therefore had insufficient gravity to hold its atmosphere and water. Its water literally evaporated into space.

But how was it possible in the first place, and why did it take so long to go (mostly) away?

Mars began with a molten core that produced a magnetosphere that protected it's atmosphere and water, but because of it's size the core cooled quickly and stopped rotating, leaving the surface exposed to solar radiation.
If Mars had been closer to Earth's size it would have been a different story.

Mars is too small and therefore had insufficient gravity to hold its atmosphere and water. Its water literally evaporated into space.

But how was it possible in the first place, and why did it take so long to go (mostly) away?

there's a theory that Mars had a internal magnetic engine like Earth has...& when it stopped, d Sun rays & storms blowed away Mars atmosphere...as d atmosphere got thinner & thinner, d water evaporated...

but it's just a theory!
;)

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non-profit org. Play4Life in Zagreb, Croatia, EU

Mars is too small and therefore had insufficient gravity to hold its atmosphere and water. Its water literally evaporated into space.

But how was it possible in the first place, and why did it take so long to go (mostly) away?

there's a theory that Mars had a internal magnetic engine like Earth has...& when it stopped, d Sun rays & storms blowed away Mars atmosphere...as d atmosphere got thinner & thinner, d water evaporated...

but it's just a theory!
;)

You're right - it's a theory - but could you please refrain from using "just" and "theory" in the same sentence? I've been battling creationists for years and every one of them has used "it's just a theory" to dismiss evolution. Drives me nuts.

An hypothesis is just conjecture it becomes a theory when there is some evidence to back it. "Just a theory" has credence, explain that to the creationists who only have an hypothesis.

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An hypothesis is just conjecture it becomes a theory when there is some evidence to back it. "Just a theory" has credence, explain that to the creationists who only have an hypothesis.

If all I manage to do is explain the scientific method and am reasonably sure they get it, I count that as a success.

That would be a great success.

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People have to change their own beliefs - all you can really do is give them some tools to do that and hope for the best.

People have to change their own beliefs - all you can really do is give them some tools to do that and hope for the best.

LOL, beliefs could get this thread moved to the politics forum.

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Mars is too small and therefore had insufficient gravity to hold its atmosphere and water. Its water literally evaporated into space.

But how was it possible in the first place, and why did it take so long to go (mostly) away?

there's a theory that Mars had a internal magnetic engine like Earth has...& when it stopped, d Sun rays & storms blowed away Mars atmosphere...as d atmosphere got thinner & thinner, d water evaporated...

but it's just a theory!
;)

You're right - it's a theory - but could you please refrain from using "just" and "theory" in the same sentence? I've been battling creationists for years and every one of them has used "it's just a theory" to dismiss evolution. Drives me nuts.

well, although evolution of organism has been proven...no evolution of species have been proven in science!

so it's just a nice theory on paper...

but, that's another topic! ;)

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non-profit org. Play4Life in Zagreb, Croatia, EU

There are documented examples of speciation (new species appearing from previous one), at least in my textbooks from a long time ago. But some of the samples also depend on what definition of a "species" is used.

Since evolution (change in the gene pool in a population over time) has also been documented and studied, and there has been a lot of lab experiments, I think that the modern Theory of Evolution by natural selection is pretty much proven as the best explanation and likely correct. It might be harder to prove that speciation occurs from evolution since it takes longer to watch it happen or to test, and the definition of a species is so hard to pin down, but I think there is enough evidence.

There are documented examples of speciation (new species appearing from previous one), at least in my textbooks from a long time ago. But some of the samples also depend on what definition of a "species" is used.

Since evolution (change in the gene pool in a population over time) has also been documented and studied, and there has been a lot of lab experiments, I think that the modern Theory of Evolution by natural selection is pretty much proven as the best explanation and likely correct. It might be harder to prove that speciation occurs from evolution since it takes longer to watch it happen or to test, and the definition of a species is so hard to pin down, but I think there is enough evidence.

no there isn't!

1. there's no exact example of evolution of one species into another!
2. the modern science explains a problem with monkey & human DNA, like a not a big deal...but that same thing happening among horses, donkeys & zebras - also mammals - (mules, hinny & zebroids) makes infertile animals...check the chromosomes in humans & monkeys...also in horses & donkeys...
;)

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non-profit org. Play4Life in Zagreb, Croatia, EU

There are documented examples of speciation (new species appearing from previous one), at least in my textbooks from a long time ago. But some of the samples also depend on what definition of a "species" is used.

Since evolution (change in the gene pool in a population over time) has also been documented and studied, and there has been a lot of lab experiments, I think that the modern Theory of Evolution by natural selection is pretty much proven as the best explanation and likely correct. It might be harder to prove that speciation occurs from evolution since it takes longer to watch it happen or to test, and the definition of a species is so hard to pin down, but I think there is enough evidence.

no there isn't!

1. there's no exact example of evolution of one species into another!
2. the modern science explains a problem with monkey & human DNA, like a not a big deal...but that same thing happening among horses, donkeys & zebras - also mammals - (mules, hinny & zebroids) makes infertile animals...check the chromosomes in humans & monkeys...also in horses & donkeys...
;)

And you think we're the same species we were before we acquired the average 2.1% Neanderthal genes in our DNA?

There are documented examples of speciation (new species appearing from previous one), at least in my textbooks from a long time ago. But some of the samples also depend on what definition of a "species" is used.

Since evolution (change in the gene pool in a population over time) has also been documented and studied, and there has been a lot of lab experiments, I think that the modern Theory of Evolution by natural selection is pretty much proven as the best explanation and likely correct. It might be harder to prove that speciation occurs from evolution since it takes longer to watch it happen or to test, and the definition of a species is so hard to pin down, but I think there is enough evidence.

no there isn't!

1. there's no exact example of evolution of one species into another!
2. the modern science explains a problem with monkey & human DNA, like a not a big deal...but that same thing happening among horses, donkeys & zebras - also mammals - (mules, hinny & zebroids) makes infertile animals...check the chromosomes in humans & monkeys...also in horses & donkeys...
;)

And you think we're the same species we were before we acquired the average 2.1% Neanderthal genes in our DNA?

you can't talk about an average of 2,1%...why?
http://www.rawstory.com/2015/10/how-a-one-night-stand-in-the-ice-age-affects-us-all-today/comments/
not all of us have a same gene pool...

& it's one thing to have sex within a species or same genus (homo)...
totally other thing is to have sex with subfamily (hominae) or family (hominidae)!

but if anyone is interested & wanted to prove me wrong...maybe he can sacrifice himself (for research purposes) & breed with some chimp or gorilla...just to see if there will be an offspring?
& if there's an offspring, will it be fertile?
B)

---

non-profit org. Play4Life in Zagreb, Croatia, EU

There are documented examples of speciation (new species appearing from previous one), at least in my textbooks from a long time ago. But some of the samples also depend on what definition of a "species" is used.

Since evolution (change in the gene pool in a population over time) has also been documented and studied, and there has been a lot of lab experiments, I think that the modern Theory of Evolution by natural selection is pretty much proven as the best explanation and likely correct. It might be harder to prove that speciation occurs from evolution since it takes longer to watch it happen or to test, and the definition of a species is so hard to pin down, but I think there is enough evidence.

no there isn't!

1. there's no exact example of evolution of one species into another!
2. the modern science explains a problem with monkey & human DNA, like a not a big deal...but that same thing happening among horses, donkeys & zebras - also mammals - (mules, hinny & zebroids) makes infertile animals...check the chromosomes in humans & monkeys...also in horses & donkeys...
;)

And you think we're the same species we were before we acquired the average 2.1% Neanderthal genes in our DNA?

you can't talk about an average of 2,1%...why?
http://www.rawstory.com/2015/10/how-a-one-night-stand-in-the-ice-age-affects-us-all-today/comments/
not all of us have a same gene pool...

& it's one thing to have sex within a species or same genus (homo)...
totally other thing is to have sex with subfamily (hominae) or family (hominidae)!

but if anyone is interested & wanted to prove me wrong...maybe he can sacrifice himself (for research purposes) & breed with some chimp or gorilla...just to see if there will be an offspring?
& if there's an offspring, will it be fertile?
B)

A bit off topic now but here is Svante Pääbo about human genom.
https://www.ted.com/talks/svante_paeaebo_dna_clues_to_our_inner_neanderthal?language=sv