evidence that life started ~4.1 million years ago

http://phys.org/news/2015-10-life-earth-billion-years-agomuch.html

This evidence points to life starting much earlier than scientists originally thought and before the massive bombardment of the inner solar system that many scientists assume would have surely wiped out any life on Earth. This implies that life may have indeed been wiped out but then quickly restarted afterwards. If that is what happened i.e. it quickly restarted so life started twice on Earth, that has profound implications for it means abiogenesis on Earth wasn't just a freak one-off fluke but rather probably readily occurs wherever conditions are right for it anywhere in the universe.
If that is right, I think we shouldn't be too surprised if we discover fossilized microbes on, say, Mars.

This implies to me that life may be common throughout the universe. But this is all assuming this latest evidence stands up to scrutiny and time. I am not a geochemists so cannot comment on that.

But note I think we are only talking here about the possibility of boring microbe life being common throughout the universe, not intelligent life. I think judging purely from the extraordinary length of time it took for the first animals with a brain to evolve on Earth from their microbial ancestors, which took up most of the evolution history of life on Earth, the evolutionary step from microbe to intelligent life must be a very difficult one.

Originally posted by humy
This implies that life may have indeed been wiped out but then quickly restarted afterwards.

Life is extremely resistant and the most reasonable explanation is that it wasn't wiped out.
I have always held that abiogenesis events may actually be quite common but that we haven't looked for them nor would we find them easily anyway. However, I don't think speculation about bombardment is evidence that abiogenesis took place twice.

If that is right, we shouldn't be too surprised if we discover fossilized microbes on, say, Mars.
We shouldn't be too surprised anyway given that meteorites should have carried life between the two planets. If anything we should be surprised if we don't find them.
More interesting will be if we find they are not obviously related to life on earth.

I think judging purely from the extraordinary length of time it took for the first animals with a brain to evolve on Earth from their microbial ancestors, which took up most of the evolution history of life on Earth, the evolutionary step from microbe to intelligent life must be a very difficult one.
It was the step from single celled to multi-celled that took the longest. Part of the problem was that large life forms need oxygen, and it required life to change the atmosphere first. But changing atmospheres can be dangerous as it can harm the life that did the changing.

Originally posted by twhitehead

We shouldn't be too surprised anyway given that meteorites should have carried life between the two planets.

I have always been skeptical of the assumption that living surviving microbes can be carried within meteorites from one planet to another and for several reasons. One reason is that, for a planetary rock to reach escape velocity as a result of a big impact, wouldn't the kinetic energy that thrown it at such massive velocity have heated it up to its core to something roughly like ~1000C ? -that would be enough to roast to death the toughest microbes on Earth. If you hit a nail with a hummer and then feel it, you may notice it has got hot to the touch. Now imagine the kind of energy needed for the much larger impact required to knock a rock into escape velocity off a planet; the heating effect on the rock would be surely be much greater than that of a hummer hitting a nail and I have observed a nail get so hot from just hummering that it burns me if I touch it.

Originally posted by humy
One reason is that, for a planetary rock to reach escape velocity as a result of a big impact, wouldn't the kinetic energy that thrown it at such massive velocity have heated it up to its core to something roughly like ~1000C ?

We have meteorites from Mars that show no sign of being heated up to that temperature.

http://www.astrobio.net/news-exclusive/taking-the-temperature-of-a-martian-meteorite/


If you hit a nail with a hummer and then feel it, you may notice it has got hot to the touch. Now imagine the kind of energy needed for the much larger impact required to knock a rock into escape velocity off a planet; the heating effect on the rock would be surely be much greater than that of a hummer hitting a nail and I have observed a nail get so hot from just hummering that it burns me if I touch it.
I think you will need a bit more than that analogy to prove your case.

Originally posted by humy
I have always been skeptical of the assumption that living surviving microbes can be carried within meteorites from one planet to another and for several reasons. One reason is that, for a planetary rock to reach escape velocity as a result of a big impact, wouldn't the kinetic energy that thrown it at such massive velocity have heated it up to its core to some ...[text shortened]... a nail and I have observed a nail get so hot from just hummering that it burns me if I touch it.

Don't forget, the meteorite that hits Earth would be going thousands of km/hour. The journey through Earth's atmosphere would only be a few seconds, say one minute. Thermal inertia would prevent the center from heating very much. Even hitting the Earth would not heat the center that much unless it was a very large impactor.

You would want the rock to crumble in order for whatever microbes inside to have a chance at a new life on Earth but that doesn't mean every bit of the meteorite would be destroyed.

My question would be, supposing we found life of some kind on Mars, would it have the same general shape as ours, DNA, RNA and double helix and so forth?

If not, it would point to an independent development of life and that in turn would imply life is everywhere in the universe that has even halfway habitable conditions for life.

Originally posted by twhitehead
We have meteorites from Mars that show no sign of being heated up to that temperature.

http://www.astrobio.net/news-exclusive/taking-the-temperature-of-a-martian-meteorite/


[b]If you hit a nail with a hummer and then feel it, you may notice it has got hot to the touch. Now imagine the kind of energy needed for the much larger impact required to kn ...[text shortened]... ns me if I touch it.
I think you will need a bit more than that analogy to prove your case.[/b]

But note your link uses an analogy with:

“...If you take a watermelon seed between your fingers and squeeze it, if there’s an open surface upward where it isn’t confined, it’ll shoot out at high speed. ...”

-miner point I admit.

+ although I accept their evidence at least as valid circumstantial evidence, I just have to reserve judgement on it because they appear to make the assumption, which, I think rather unscientifically, didn't make explicit, that the rock couldn't have been re-magnetized sometime AFTER it was ejected from the planet by an impact but BEFORE it landed on Earth. If that assumption is wrong, their reasoning doesn't prove that the only explanation why the rock is still magnetized is because it was never heated much when it was ejected, which means for all we know it might have been greatly heated when it was ejected and then re-magnetized later. They didn't say in that link that that possibility could be ruled out nor why so.
I speculate (and I admit this is currently just speculation on my part ) one way this re-magnetized could have happened is by it passing very close to Jupiter which has massively strong magmatic fields much greater than that of the Earth; -but I admit I am not sure if some heating of the rock would be required for such re-magnetization or if it could happen even when the rock is still very cold, as it would be when so far from the sun around Jupiter. If some heating of the rock IS required, how about it passing extremely close to the sun and thus gets hot that way and then, as it slowly cools as it moves away of the sun, it could be exposed to intense magnetic fields from the sun as it moves away of the sun thus the magnetize becomes permanently fixed in it? Speculation I admit but, still, why not?

Originally posted by sonhouse


My question would be, supposing we found life of some kind on Mars, would it have the same general shape as ours, DNA, RNA and double helix and so forth?

Not sure how likely it would be for DNA to evolve independently from a totally different biogenesis origin. But I have thought of a way around that: Say we found life on Mars with DNA; the next thing we can then look for is to see if it has the same codon language, which is after all totally arbitrary and could be made different without any biological cost, as our own life: if it does, that would be an unlikely coincidence thus we can say that Mars life is almost certainly related to Earth life. But, if the codon language is totally different, I would take that as very strong evidence short of proof that it has totally independent origins as, judging from Earth's life, because all modern earth life shares the same codon language, this indicates that once a codon language has first formed, it is very difficult for evolution to change it i.e. life becomes permanently stuck with it exactly the way it was when it first formed.

Originally posted by humy
But note your link uses an analogy with:

I didn't say analogies are out. I merely said yours was insufficient. Theirs doesn't prove a whole lot either, but it does highlight a flaw in your analogy ie that pounding repeatedly on a nail is not the same pattern of forces as ejecting material. Try hitting a pile of sand really hard with your hammer. Lets see how many grains melt. I bet that some grains will fly off with significant velocities and won't even experience a single degree of temperature increase.

I do think that heating a rock sample to 1000C as you suggest would leave clear effects on the rock which would be easily identifiable. The article in question was attempting to distinguish much lower temperatures.

Originally posted by humy
But note your link uses an analogy with:

“...If you take a watermelon seed between your fingers and squeeze it, if there’s an open surface upward where it isn’t confined, it’ll shoot out at high speed. ...”

-miner point I admit.

+ although I accept their evidence at least as valid circumstantial evidence, I just have to reserve judgement on it because ...[text shortened]... sun thus the magnetize becomes permanently fixed in it? Speculation I admit but, still, why not?

That would depend on the level of magnetization found in the fossil meteorite. If it is less than Earth maybe it could have been magnetized by Earth's magnetic field, it would be in that field as it heats up and another thing, is there isotropy in the level of the field vs the depth of the material, that is to say, does the field weaken as it gets to the center of the rock? That would be another indicator of the level of field it encountered to get whatever level was measured.

BtW, on another note, we have several version of sputtering tools and this one used for production, depositing SiC (silicon carbide) was running half the dep rate as other machines, The SiC target has a ring of strong magnets in it, an outer ring of north field and a line of magnets in the center of the north field magnets, they are south field.

So we have been having this issue where that target was not depositing at the same rate, usually up to 50 angstroms per pass (the platen with parts on it goes back and forth slowly over the target) but now down to 17 odd angstroms per pass.

So with that in mind, we were trying to figure out why. So I talked them into buying a new instrument, a DC magnetometer, goes from about 1 or so gauss to 20,000 gauss, 2 tesla, so I measured the field on the working targets and found a positive number, maybe indicating south field around the perifery of the magnets but on the suspect target, found the right side at plus 40, 50,30, etc. but the left side, minus 20,30, and so forth. So it looks like the magnets inside have either been turned upside down on one part of the ring or the magnets have somehow deteriorated, which we won't be able to troubleshoot for a couple of weeks for reasons that would take too many words to show🙂 But the magnetometer I think has paid for itself already!

This wikipedia page touches on this. The late heavy bombardment theory isn't a universally accepted theory and there is more evidence than just this:

https://en.wikipedia.org/wiki/Late_Heavy_Bombardment#Geological_consequences_on_Earth

Originally posted by DeepThought
This wikipedia page touches on this. The late heavy bombardment theory isn't a universally accepted theory and there is more evidence than just this:

https://en.wikipedia.org/wiki/Late_Heavy_Bombardment#Geological_consequences_on_Earth

I just read it and didn't realize the huge level of uncertainty about it. They cannot even agree with certainty whether there existed oceans or liquid water at the time, which I think is a pretty basic fundamental thing. I take it that no liquid water before the assumed bombardment would imply no previous life.

Originally posted by humy
I just read it and didn't realize the huge level of uncertainty about it. They cannot even agree with certainty whether there existed oceans or liquid water at the time, which I think is a pretty basic fundamental thing. I take it that no liquid water before the assumed bombardment would imply no previous life.

I don't think it's a problem for life per say, but they are claiming a photosynthesiser based on Carbon 13/14 rations.. I've heard the opinion that water is a problem for early life as it tends to destroy complex molecules. So if one had some sort of extremophile it makes sense. But photosynthesis requires water - unless there's some other pathway for storing energy. So if they have a photosynthesiser they'd need more than trace quantities of water present before the late heavy bombardment. Although I think that's quite likely, there's no reason I know of to think that water wasn't part of the mix of stuff that conglomerated into the earth.

So:
Either these are not photosynthesisers and there's something wrong with their analysis or water was present on the pre-late heavy bombardment earth.

Originally posted by DeepThought
I don't think it's a problem for life per say, but they are claiming a photosynthesiser based on Carbon 13/14 rations.. I've heard the opinion that water is a problem for early life as it tends to destroy complex molecules. So if one had some sort of extremophile it makes sense. But photosynthesis requires water - unless there's some other pathway for ...[text shortened]... omething wrong with their analysis or water was present on the pre-late heavy bombardment earth.

http://www.nature.com/scitable/definition/codon-155

Short discussion of Codon's, so GAC is Glutamine and so forth.

So you are saying if we show an alien life form uses Glutamine but the codon is say CAG instead of GAC, that would indicate an independent development of life?

Originally posted by sonhouse

So you are saying if we show an alien life form uses Glutamine but the codon is say CAG instead of GAC, that would indicate an independent development of life?

Not exactly because only one codon difference would certainly not be adequate evidence of independent origin. This is because that would mean all the other codons would be the same and so many just happen by pure chance to independently end up exactly the same which would be far too much of a coincidence and thus, despite one codon being different, I would still conclude common origin.

I think what would really prove independent origin is if all or nearly all the codons of that alien life were completely different from that of Earth's life because that is exactly what I would expect from independent origin and because I think that would be very difficult to explain with a common origin theory (partly because there is no biological cost of having the codon language being one way rather than another thus evolution wouldn't favour one over the other, and partly because, once a codon language first forms, it is near-impossible for evolution to change it as the cellular biology would evolve to totally depend on that exact original codon set ) but trivial to explain with independent origin.

Incidentally, the same kind of reasoning + observation of common codon language in Earth's life proves that at least all the life on Earth we have studied the codon language of has common origin -excellent indirect but powerful evidence of evolution.

(I assume here you are talking to me but responded to his post by mistake )

Originally posted by sonhouse
http://www.nature.com/scitable/definition/codon-155

Short discussion of Codon's, so GAC is Glutamine and so forth.

So you are saying if we show an alien life form uses Glutamine but the codon is say CAG instead of GAC, that would indicate an independent development of life?

My point wasn't as technical as that. It's a matter of what the evidence means. If there was little water before the LHB (late heavy bombardment) then that would fit with some ideas, but not with photosynthesisers which is what the article was saying they'd found in their zircon grain. If there was water then there's questions about how our really distant ancestors could avoid being destroyed before we got going at all or for that matter whether there was an LHB at all. There's several fields of study impinging on this and the correct answer tells us things about the formation of the solar system and the origins of life or alternatively laboratory errors. Even if it's the latter then that's important information.