World's Oldest Rocks Found

Smivs writes "The BBC reports that Earth's most ancient rocks, with an age of 4.28 billion years, have been found on the shore of Hudson Bay, Canada. Writing in Science journal, a team reports finding that a sample of Nuvvuagittuq greenstone is 250 million years older than any rocks known. It may even hold evidence of activity by ancient life forms. If so, it would be the earliest evidence of life on Earth — but co-author Don Francis cautioned that this had not been established. 'The rocks contain a very special chemical signature — one that can only be found in rocks which are very, very old,' he said."

Comments

Worlds oldest found rocks found!

[narcberry]

Isn't it inaccurate to say "World's oldest rocks found" ? I'm a fan of Schroedinger and all that, but just because their the oldest we've observed doesn't mean they are the oldest.

Re:Worlds oldest found rocks found!

[Anonymous Coward]

The 'oldest' (or largest, smallest etc...) is always based on known measurable things. It isn't the the oldest person is the absolute oldest person in the world, just the oldest known. There could have been one person who lived long before we recorded it who lived longer than anyone today, albiet unlikely. It is likely there are older rocks, in fact it is almost inevitable there are older ones, especially if they find traces of life in them. These are just the oldest verified and recorded that we know of.

Re:Worlds oldest found rocks found!

[Anonymous Coward]

Radiometric methods give the date of a *rock*, not the date of the formation of its constituent atoms (which you can't measure because of the "memoryless" property of exponential decay). The idea is that if samarium desintegrates on its way from space to the Earth, it stops being samarium. So by definition, all the samarium found in a rock is "fresh" when the rock is formed. When it desintegrates its products (such as neodymium-142) are trapped in the rock.

Re:Worlds oldest found rocks found!

[KGIII]

I dated a rock once. Yeah, it was a hard relationship. Most of the time she was just stoned though.

Hey, bad puns. Don't take them for granite.

Yeah, I'll be here all night. (I really should learn to drink less or post as AC.)

Re:Worlds oldest found rocks found!

[Anonymous Coward]

You're close.

"1) It penetrated the surface of the planet (Duh!!) and caused a large amount of the core of our forming planet to get whacked out into orbit."

It's kind of the other way around. The core of the impacting body was mostly incorporated into the Earth (making it, on average, denser), and the Moon formed mostly out of the mantle/outer part of the impacting body and parts of the Earth that were blown into orbit, making it, on average, lighter, and the lunar material has a more refractory composition (i.e. more depleted of volitile material).

"3) The force of the blast meant that the effective entire crust of the earth was again submerged into the insides of the earth."

Hmmmm.... well, most of the entire surface became molten, but I wouldn't describe the process as "suberged", more like "melted", although the dense stuff delivered by the impactor sank into the core.

"The last part is the most important to this article, as there are very very few "rocks" that can survive that sort of hear/pressure without being changed beyond recognition. One of these is Zircon."

Zircon isn't a rock, it's a mineral found in rocks, usually at a percent or less by volume, and it is harder than most minerals to "reset" it by heating. The rock in question is described as an amphibolite (a rock rich in minerals of the amphibole group, although they describe it as a "faux amphibolite", so it's an odd one). Zircon is relevant to the story because it contains uranium, and it is therefore a useful mineral for the U/Pb radiometric dating technique.

The really exciting part is that these rocks also have quartz and magnetite (Fe3O4) layers implying they were originally layered, sedimentary rocks (they've subsequently been heated and compressed to form a metamorphic rock, but the sedimentary signatures are apparently still there). Previously there were only individual mineral grains known that old (also zircons), with the rest of the rock heated and deformed subsequently so that little of the original structure remained.

"The belief is that these were either formed on earth prior to the impact or came on the thing that hit us (I can't remember which)."

They formed on Earth after the Moon-forming impact. That's thought to have occurred within the first 100 million years or so of Earth history, and there are no intact mineral grains on Earth that old (so far), and none are really expected because so much was melted by the event. For older stuff you have to look at meteorites.

Exciting future prospects

[FoboldFKY]

When asked for comment on what they intended to do with the rocks now that they had them, the lead researcher responded:

"Oh well, you know. Put them on a shelf. Maybe look at them from time to time. We might, when people come around to visit, take them down and let people not touch them! It's all terribly exciting... in fact, I think I need a lie-down."

Re:There is hype in the article

[cbreaker]

No. Intelligent Design cannot be taught in a scientific manner, unless it is to say "There was no Intelligent Design."

The whole "teach the controversy" is an attempt to trick people into teaching ID, and is a means of validating it.

Discovery of world's oldest rocks challenged (link

[Anonymous Coward]

Not everyone agrees.

This was covered a few days ago on New Scientist...

http://environment.newscientist.com/article/dn14818-discovery-of-worlds-oldest-rocks-challenged-.html

Re:4 Billion years old? I don't think so.

[dakameleon]

I don't know about "50 years", or how deeply this counts as documentation, but there's a decent run-down here: http://en.wikipedia.org/wiki/Allegorical_interpretations_of_Genesis#Contemporary_Christian_considerations

The "money quotes" are from Pope John Paul II -

The Bible itself speaks to us of the origin of the universe and its make-up, not in order to provide us with a scientific treatise, but in order to state the correct relationships of man with God and with the universe.

... pointing out that the Pope does not consider it to be taken literally;

Sacred Scripture wishes simply to declare that the world was created by God, and in order to teach this truth it expresses itself in the terms of the cosmology in use at the time of the writer.

... pointing out that it was written for an audience, not an 'absolute truth';

The Sacred Book likewise wishes to tell men that the world was not created as the seat of the gods, as was taught by other cosmogonies and cosmologies, but was rather created for the service of man and the glory of God.

... pointing out that its purpose is to put forward the 'Christian'/monotheistic view, as opposed to the views of other religions, such as the contempary polytheistic religion of the Romans, and again not altogether incompatible with science.

The full discourse from the pontiff is linked on Wikipedia, but it's here for your convenience: http://www.ewtn.com/library/PAPALDOC/JP2COSM.HTM

HTH.

Re:Discovery of world's oldest rocks challenged (l

[rockhopjohn]

As is stated in the New Scientist article, the technique used might actually date the protolith (the material from which this rock formed) and not the actual rock itself. From a geochronologist's stand point, this rock is actually 3.8 billion years old, based on the U-Pb zircon age given in the Science article. The age determination for the reigning oldest rocks discovered was found through U-Pb zircon work. The authors are very clear to point out that this 4.28 Ga date is not a definitely age for the rock. Gotta love the media jumping head long in front of the science.

Well, that depends

[ChePibe]

On how they "teach the controversy".

The way it was handled in my high school science class was simple: a discussion of what "science" meant. Science, after all, is more of a method of discovery by certain rules than a true monolith (such as "science says"). This was then distinguished from spiritual approaches by focusing on physical evidence, falsifiability, etc.

Essentially, the teacher better defined science and distinguished it from religion. She then stated that, as we were in science class, we would learn the scientific take. We were free to believe as we wished - as is the fundamental right of every man, enshrined in the First Amendment and various case law interpreting it - but, regardless of what we believed, we would learn the scientific take in a science class - it only meant sense.

That, to me, is the appropriate way to handle the situation. I particularly liked the way it reminded us more of the scientific method and of the epistemological differences between the hard sciences and other subjects. This planet and its people would benefit a great deal by learning the ability to approach matters in different ways and to even learn to hold two, conflicting ideas in their heads for a moment's time, if not but for the purpose of comparison. We need to trust people to think about things for themselves. Teaching epistemological approaches and focusing on process rather than product is vital to this.

Ah, bible explained after all.

[tjstork]

Looks like ancient shamans used a DWORD in the Good book to represent the age of the earth. When it was downloaded, the figure of 4.3 billion years overflowed and wrapped around to around 6000 years.

Problem solved.

It's funny though, because, you know, as much as everyone deservedly knocks the 6000 year old figure, few actually probe the ancient conceit that drove it - that is, the universe could not exist without mankind, and so, it more or less exists to serve mankind, and therefor we can spread out across the world and conquer it.

Now, with all of our fancy science of course, we know much better. We know that the universe is billions of years old, and that, we've not actually found a shred of life within it that is not from our planet. Not a peep out of SETI, a hello from another world - not even a cell on Mars- nothing. So, it really looks like, that, we can spread across the world and conquer it.

So, the upshot is that ancient man and today's scientists drew exactly the same conclusion. If we can see it, we can take it. All of this mumbo jumbo about the age of the thing doesn't matter a bit. In the mind of the Pope and Goddard alike, its -ours-.