RENEE MONTAGNE, host:
Scientists who are trying to pin down how life on earth began have a problem. Billions of years have wiped away all signs of that key biological moment. But, as NPR Science Correspondent Robert Krulwich reports, there might be somewhere else to poke around.
ROBERT KRULWICH reporting:
If you wanted to find the oldest evidence of life on earth - the oldest fossil you could find anywhere, where would you look?
Professor PETER WARD (Geological Sciences, University of Washington): I would go to the moon if they would've let me.
KRULWICH: He's not kidding. Professor Peter Ward of the University of Washington thinks the secret of life on earth may be lying, right now, on the moon.
Prof. WARD: I'm, personally, very interested in going to look, as a matter of fact.
KRULWICH: But, no one with a rocket has invited him to the moon. Not yet. But, here is his argument: our planet, he says, is about 4.6 billion years old.
Prof. WARD: Or even 4.6 and change.
KRULWICH: Okay, and the oldest evidence of life on earth...
Prof. WARD: Well, the oldest we know of is an actual fossil - and you could say, ah-hah, that definitely looks like it was once alive to me - is 3.5 billion years in age.
KRULWICH: And there are rocks with chemical traces of life. They go back 3.7 billion years. So, what we've got here then is a gap between the birth of our planet...
(Soundbite of song, “Also Sprach Zarathustra”)
KRULWICH: ...the start of the earth - followed by a billion year pause - a long blank. There are no fossils, none at all during this period. And then finally, finally...
(Soundbite of song, “The Four Seasons - Spring”)
KRULWICH: ...we get our first evidence of life - our first fossil. That is a long time to wait for life to start. And scientists have been hunting and hunting for sedimentary rocks - fossil bearing rocks that come from that missing middle period.
Prof. WARD: If only, if only we could go up to some strange unexplored spot where there's a pristine four billion year old rock.
KRULWICH: But, hard as they try, they can't find them on earth, cause rocks that old have gotten so beaten and so battered, they've probably melted.
Prof. WARD: Yeah, exactly. We have a really dynamic planet, and comets smash into one another with gay abandon and they squish each other and rocks go up and rocks go down. And the terrible thing is, when rocks go down, they get heated. And when they get squished, they get crushed, and all the pristine stuff turns into other kinds of rocks, undecipherable.
KRULWICH: So, if our planet, in effect, has erased its earliest history, what'll we do now?
(Soundbite of telephone ringing)
Mr. JOHN ARMSTRONG (Graduate Student, Washington University): Hello, this is John Armstrong.
KRULWICH: Here's an idea. A few years ago, John Armstrong and two other young graduate students - and they're all at the University of Washington - were knocking around this problem.
Mr. ARMSTRONG: You know, you just can't find samples of early earth on earth.
KRULWICH: And they were thinking, is there anyplace else we can look? And that's when, he says...
Mr. ARMSTRONG: The moon came up...
Prof. WARD: It just came up.
Mr. ARMSTRONG: ...as a possibility, yeah.
Prof. WARD: They told us - the faculty - hey, guys, how about this? We think that you will find more pristine earth rock on the moon than anywhere on the earth. And at first you go, yeah, right. Now, you guys go back to the drawing board and think again. But, in this particular case, they could support it.
KRULWICH: It is well known that four, five billion years ago, there were lots of meteors in our part of the solar system. And a lot of them hit the earth.
Prof. WARD: It was just an enormous amount of in-fall coming in from these hugely monstrous objects.
KRULWICH: And when Armstrong and his friends calculated the probably size and speed and angle of those incoming rocks, their computers said it's very, very likely that they hit the earth so hard, tons of earth - earth rock - got thrown up into space.
Mr. ARMSTRONG: And we thought, well, you know, there's all these Mars meteorites coming to earth. Is it possible for earth meteorites to go to the moon?
KRULWICH: Why not? I mean, the moon is so close.
Mr. ARMSTRONG: Exactly. Yeah, the moon's just right upstairs.
KRULWICH: So, the three young scientists concluded, almost certainly, ancient rocks from earth that very well may contain fossils, did land on the moon. And what's more, they're still there - lots of them.
Prof. WARD: The estimate is that there are from hundreds of thousands to millions of tons of earth rock on the moon.
Unidentified Man #1: Holy smoley!
Unidentified Man #1: (Laughs) Boy, do we got a slope.
Unidentified Man #2: You okay?
KRULWICH: As it happens, back in 1972, a trained geologist from Harvard -astronaut Jack Schmitt, with fellow astronaut Gene Cernan...
Unidentified Man #1: Oh, hey!
KRULWICH: ...spent hours on the moon scooping, and sometimes pulling rocks right off the surface.
Unidentified Man #2: I'm going to get this thing out, now that I got it.
(Soundbite of beeps)
(Soundbite of breathing)
(Soundbite of beeps)
KRULWICH: They put hundreds of pounds into sample bags...
(Soundbite of beeps)
Unidentified Man #2: Just don't stub your toe.
KRULWICH: ...and because astronaut Schmitt had a trained eye, he knew how to search, he could better appreciate the odd things, like bright orange lunar soil.
Professor JACK SCHMITT (Astronaut, Apollo 17): There is orange soil!
Unidentified Man: Well, don't move it until I see it.
Prof. SCHMITT: It's all over. Orange!
Unidentified Man: Don't move it till I see it. I've stirred it up with my feet.
Prof. SCHMITT: Hey, it is! I can see it from here. It's orange!
KRULWICH: So, the young grad students propose that once we figure out a way to reliably tell the difference between earth rocks and other rocks, then when people go back to the moon, if they look specifically for ancient earth rocks...
Prof. SCHMITT: Oh, man, that's incredible!
KRULWICH: We might just find, say, a 4.2 billion year old sample, and if it contained traces of earth's life, then, says Professor Ward...
Prof. WARD: There is no more interesting question in the whole cosmos than how does life start.
KRULWICH: And if there was life more than four billion years ago when the earth was very new and hot and young...
Prof. WARD: It would indicate that life began on this planet just about as soon as it could have.
KRULWICH: And that would tell us what?
Prof. WARD: That it would happen so quickly, certainly should suggest to us that life is easy to make.
KRULWICH: And if it's easy to make, then the odds go up that it's probably everywhere - all over the universe. But, of course, there are those who think fossils on the moon is a pretty wild, farfetched idea.
Professor LARRY TAYLOR (Lunar Soil Expert): Oh, yeah, it's got - you know, it's within the realm of possibility. It's just that it's - the chances of finding some of these particles - or one of the big ones - is not too good.
KRULWICH: Not too good, because - says lunar soil expert Larry Taylor - when you are standing on the moon, you can't help but notice that there's no atmosphere.
(Soundbite of beeps)
Unidentified Speaker: Oh, what a nice day. Ah! Funny, there's not a cloud in the sky, except in the earth's.
KRULWICH: So, if earth rocks ever did plummet to the moon, there was no atmosphere to slow them down.
Prof. TAYLOR: When they hit the moon, they may be hitting the moon at 50 -75,000 miles per hour.
KRULWICH: Which means, most incoming earth rocks became, ka-thump! - dust. But, says John Armstrong, you can analyze dust for signs of ancient life just like you can fossils.
Mr. ARMSTRONG: It's something that's done with old earth rocks all the time.
KRULWICH: All we have to do is learn how to separate out the earth bits.
And so, from now on, he says, whoever goes to the moon - astronauts or cosmonauts, engineers, business types, workers - whoever they may be - when they go out for a stroll on the moon, like Jack Schmitt and Gene Cernan did...
Unidentified Man #1: (Singing) I was strolling on the moon one day...
Unidentified Man #1 and #2: (Singing) in the merry, merry month of...
Unidentified Speaker #2: (Singing) ...December.
Unidentified Speaker #1: No, May...
KRULWICH: They should all be told to keep an eye out, because there could be a scoop of soil, or maybe a few rare, odd-looking rocks lying on the moon that just might contain the secret of life on earth.
Unidentified Man #1: Okay...
KRULWICH: Robert Krulwich...
Unidentified Man #1: Fantastic!
KRULWICH: NPR News in New York.
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MONTAGNE: This is NPR News.
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