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ToSeek
2004-May-14, 03:20 PM
"Rare Earth" perspective on the subject (http://www.allsci.com/mars.html)


One of the most important differences between the Earth and Mars, according to Peter Ward, is plate tectonics. On Earth, plate tectonics does everything from provide a stable global temperature, which is necessary for the evolution of complex life, to recycling chemicals to keep the volume of carbon dioxide in our atmosphere relatively uniform. It also created the continents, which helped to create the large amount of biodiversity and aids in creating the magnetic field that surrounds Earth. All of these are important to the development and maintenance of complex life, and, except for a brief time, in which volcanoes were created, it doesn’t exist on Mars.

Master258
2004-May-14, 06:15 PM
I don't know, I heard this on Coast to Coast a few nights back.

Chip
2004-May-14, 07:24 PM
Even if one felt that Mars is not a place where life could start on its own, Earth rocks (though rare) have been landing on Mars for many millions of years. Is it illogical to surmise that if microbial life were confirmed on Mars, its origin may have been via Earth meteorites?

Squink
2004-May-14, 09:48 PM
This bit from the linked article rather raised my hackles:
What if, suddenly, plate tectonics were to suddenly stop? First, the Earth’s core, which is extremely hot, would stop emanating heat and the plates that move, which is caused by the heat, are somehow changed so they become immobile. This may have been one of the processes by which plate tectonics stopped on Mars. The heat stopped emanating? Like it suddenly decided to slip into the 4th dimension or something? [-( I'd like the article better if they instead muttered about Mars' smaller size increasing the heat transfer from and frictional braking of the internal dynamo, and that leading to a loss of magnetic field and stoppage of plate movement.
Over here (http://physicsweb.org/article/news/3/5/1/1) the talk is all about an era of plate movements on Mars that lasts "a few hundred million years." Judging from post Noachian earth, that's long enough for bacteria to form via abiogenesis.
I'd be more convinced by the articles arguments about the unlikelyhood of multicellular eukaryotes evolving on Mars if anyone could point to a good argument as to why complex multicellular life forms took billion of years to evolve on Earth. Without understanding that mystery, I don't see how we can credibly speculate on how fast things might have evolved on Mars.

beskeptical
2004-May-15, 12:42 AM
There's a dif between 'no life' and 'microbial life'. It seems to be lost in the article.

If there is microbial life on any planet or moon in our solar system, that has a huge impact on the Drake equation in my mind. It's a big Universe and it's been here a long time. If microbes are anywhere besides Earth, the chances for evolution to intelligent beings somewhere in the Universe would be pretty high.

Chip
2004-May-15, 07:00 AM
Yeah! -- What beskeptical said! :D

bobjohnston
2004-May-17, 02:43 AM
Even if one felt that Mars is not a place where life could start on its own, Earth rocks (though rare) have been landing on Mars for many millions of years. Is it illogical to surmise that if microbial life were confirmed on Mars, its origin may have been via Earth meteorites?

It's a whole lot harder to get rocks off the Earth than off of Mars. The escape velocity is 2.2 times greater for the Earth, meaning it takes about 5 times the ejection energy to get it off the surface. I don't think biological material will survive.

ToSeek
2004-May-17, 04:18 AM
There's a dif between 'no life' and 'microbial life'. It seems to be lost in the article.

If there is microbial life on any planet or moon in our solar system, that has a huge impact on the Drake equation in my mind. It's a big Universe and it's been here a long time. If microbes are anywhere besides Earth, the chances for evolution to intelligent beings somewhere in the Universe would be pretty high.

I still lean toward the "Rare Earth" hypothesis that bacteria are common but that anything more advanced is rare. Still, it would be awesome to find life on Mars that wasn't related to terrestrial life.

beskeptical
2004-May-17, 04:44 PM
....it takes about 5 times the ejection energy to get it off the surface [of Earth]. I don't think biological material will survive.I'm not sure about the ejection and explosion survival but IIRC, bacteria survived after 2 years in space on some Lunar equipment. (Not that I think Earth life has been transferred to Mars via meteorites.)

Squink
2004-May-17, 07:07 PM
IIRC, bacteria survived after 2 years in space on some Lunar equipment. (Not that I think Earth life has been transferred to Mars via meteorites.) There's at least suggestive evidence (http://www.google.com/search?as_q=&num=10&hl=en&ie=ISO-8859-1&btnG=Google+Search&as_epq=million+year+old+bacte ria&as_oq=&as_eq=&lr=&as_ft=i&as_filetype=&as_qdr= all&as_nlo=&as_nhi=&as_occt=any&as_dt=i&as_sitesea rch=&safe=off) that bacteria might survive long enough to participate in galactic panspermia.

Chip
2004-May-18, 12:39 AM
It's a whole lot harder to get rocks off the Earth than off of Mars...I don't think biological material will survive.

Quite right, but I was thinking over many millions of years, and as far as a successful seeding of Mars goes, if Mars was more temperate when a microb-inhabited Earth rock landed - though very rare, it would only have to happen once.

Of course its been suggested that the opposite could have happend, in which case we're all Martians. :wink: