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So, where did the water on Mars come from?
The Toronto Star ^ | 3/7/04 | Terence Dickinson

Posted on 03/07/2004 2:21:58 AM PST by LibWhacker

The Mars rover Opportunity's examination of Martian rocks last week provided the first convincing evidence that our neighbour world was once "awash" in water, as one NASA scientist described it.

But where did the water come from? And why does Mars have no liquid water now, while Earth apparently has been covered with the stuff for 4 billion years?

Scientists are just beginning to piece the story together, and it goes right back to the beginning.

Mars, like Earth, was formed from dusty and rocky debris left over after the sun was born 4.57 billion years ago.

Initially, there were more planets in our solar system than the nine we recognize today, perhaps twice as many.

Earth suffered an especially brutal encounter with one of them 4.52 billion years ago, when a wayward body the size of Mars smashed into it. Our planet was almost split in two. Molten rock was splashed out into space and later condensed in orbit to form the moon.

The impact blasted the Earth's atmosphere into space, boiled off any water and turned our planet's surface into a sea of molten rock. Venus, Mercury and Mars, the other approximately Earth-sized planets, likely suffered similar collisions around the same time, though no large moons remain orbiting those worlds.

By 4.4 billion years ago, the Earth's surface had cooled enough to have a solid crust.

The formation of the planets was an inefficient process and for millions of years the Earth and the other planets were bombarded by what astronomers call planetesimals — essentially leftover chunks from the birth of the solar system, up to a few hundred kilometres in diameter.

By 3.9 billion years ago, the bombardment began to subside, but evidence for it is visible in binoculars when you look at the craters on the moon, the majority of which date from 3.9 billion to 4.4 billion years ago, when the planetesimals were raining down.

The puzzling part of this is that Earth's oceans, and now probably the water that was on Mars, both date from this period. Where did it come from?

The only reasonable answer is comets. Comets were formed farther out from the sun than Earth, but in such abundance that they also rained down in the early solar system.

They came into the inner solar system as frozen water — giant snowballs — depositing vast amounts of liquid water on Earth and apparently on Mars too.

Because of Earth's distance from the sun, our planet's surface temperature remains, on average, between the freezing and boiling points of water.

Moreover, Earth's atmosphere acts like a lid, trapping most of the moisture.

Mars, on the other hand, is too far from the sun to stay warm and too small to gravitationally trap a dense enough atmosphere to bottle up what warmth it does have.

The comet-fed oceans it likely had either escaped into space or ended up trapped in cold storage as permafrost.

To test these ideas, the Mars rovers will continue their explorations.

The comet part of the equation will be investigated this summer, when two comets float into Earth's sky in May.

They are expected to be bright enough to allow astronomers to examine them for further clues to the origin of water on Earth and Mars.

--------------------------------------------------------------------------------
Terence Dickinson is editor of Skynews magazine and author of books for backyard astronomers.


TOPICS: Miscellaneous; News/Current Events
KEYWORDS: bigsplash; catastrophism; chondrite; comet; comets; h2o; impact; louisfrank; mars; origin; velikovsky; water
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1 posted on 03/07/2004 2:21:58 AM PST by LibWhacker
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To: LibWhacker
To have been awash with water, Mars had to have two things, the needed temperature range and sufficient atmosphere.
2 posted on 03/07/2004 2:27:50 AM PST by cynicom
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To: LibWhacker
The puzzling part of this is that Earth's oceans, and now probably the water that was on Mars, both date from this period. Where did it come from?

The only reasonable answer is comets.

It is reasonable. Who first proposed comets as the source of Earth's water?

3 posted on 03/07/2004 2:37:08 AM PST by ngc6656 (Freepaholics Anonymous advisory: Don't freep and drive.)
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To: ngc6656
I first read about it in "The Big Splash" By Dr. Louis Frank (in part).
4 posted on 03/07/2004 2:49:36 AM PST by Smokin' Joe (As the oldest generation dies, the memory of liberty fades into obscurity, replaced by an impostor)
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To: ngc6656
Don't know. That's a fairly recent idea, isn't it?
5 posted on 03/07/2004 2:50:04 AM PST by LibWhacker
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To: cynicom
To have been awash with water, Mars had to have two things, the needed temperature range and sufficient atmosphere.

It is hard to imagine Mars had bodies of water approaching the size of Earth's oceans. Thinking regionally, one can imagine the formation of temporary streams, ponds, lakes, perhaps even small seas as comets of various sizes collided with Mars.

6 posted on 03/07/2004 2:56:22 AM PST by ngc6656 (Freepaholics Anonymous advisory: Don't freep and drive.)
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To: ngc6656
Must have been a hell of a lot of comets to fill the oceans. Talk about bad weather . . .
7 posted on 03/07/2004 2:56:35 AM PST by Neanderthal
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To: LibWhacker
Martian lawn sprinklers.
8 posted on 03/07/2004 3:13:56 AM PST by bikerman
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To: LibWhacker
Now the question is, does Mars have enough water now to sustain a self contained colony.
9 posted on 03/07/2004 3:18:07 AM PST by Simmy2.5 (Kerry. When you need to ketchup...)
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To: ngc6656
Yep, I don't think there is much doubt that Mars was much a warmer place in the early Solar System, and probably had a much more substantial atmosphere as well.
10 posted on 03/07/2004 3:22:31 AM PST by LibWhacker
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To: LibWhacker
I was always suspect of those evil hydrogen clouds roaming the galaxy but questioned which star system was hording all the oxygen clouds???
11 posted on 03/07/2004 3:27:15 AM PST by JoeSixPack1 (POW/MIA, Bring 'em home, NOW!)
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To: LibWhacker
in a word, GOD.
12 posted on 03/07/2004 3:27:24 AM PST by Joe Boucher (G.W. Bush in 2004)
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To: Smokin' Joe
Maybe Dr. Grafenberg knows.
13 posted on 03/07/2004 3:29:51 AM PST by Gazoo
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To: Simmy2.5
It'd be so cool if we could go there, drill down and hit vast reserves of fresh water. It could conceivably allow us to go there and stay for good.
14 posted on 03/07/2004 3:29:56 AM PST by LibWhacker
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To: Smokin' Joe; LibWhacker
A Google search turns up that Dr. Louis Frank proposed in the 1990s that Earth's atmosphere is continuously receiving water vapor as many small comets evaporate there. Other sites that turned up in the search allude to the decades old theory put forth by planetary scientists that Earth's oceans were the product of the impact of large comets.

Study of Comet Hale-Bopp revealed that most of its water is of the heavy type containing the heavier hydrogen isotope named deuterium. If Hale-Bopp was a typical large comet, why then doesn't our oceans contain greater amounts of heavy water, they point out. Investigations continue.

15 posted on 03/07/2004 4:03:33 AM PST by ngc6656 (Freepaholics Anonymous advisory: Don't freep and drive.)
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To: LibWhacker
But where did the water come from?

There is no water. Rather than ask where it came from why not first ask, where did it go?

16 posted on 03/07/2004 4:37:07 AM PST by MosesKnows
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To: LibWhacker
The impact blasted the Earth's atmosphere into space

Was there an atmosphere to blast into space? I thought the impact is what caused earth to have a moon and an atmosphere.

17 posted on 03/07/2004 4:40:44 AM PST by MosesKnows
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To: MosesKnows
Easy. The Bush administration destroyed the martian atmosphere and used all the water.
18 posted on 03/07/2004 5:19:09 AM PST by Crazieman
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To: LibWhacker
The formation of the planets was an inefficient process and for millions of years the Earth and the other planets were bombarded by what astronomers call planetesimals — essentially leftover chunks from the birth of the solar system, up to a few hundred kilometres in diameter.

Don't you just love moronic sentences like this?
19 posted on 03/07/2004 5:21:04 AM PST by aruanan
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To: LibWhacker
I find the article very interesting because I had never previously considered the question of where Earth's water came from. Guess I assumed it somehow occured here naturally, just like other compounds. What a strange notion to imagine it came from comets.

But when you look at the vast oceans, is it really possible that all that water comes from melted comets? I really can't believe that. Are there other scientific theories, in particular ones that envision that water was somehow created on Earth?
20 posted on 03/07/2004 5:21:07 AM PST by governsleastgovernsbest
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To: LibWhacker
But where did the water come from?

The Culligan Man?

21 posted on 03/07/2004 5:21:16 AM PST by mewzilla
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To: LibWhacker
So if the earth had been just a little closer or farther from the sun, no people. If we had been hit by just a few more comets, no dry land, and no people. Hmmm.
22 posted on 03/07/2004 5:24:19 AM PST by Arthur McGowan
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To: LibWhacker
Interesting article. Thanks for posting it.
23 posted on 03/07/2004 5:24:57 AM PST by PGalt
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To: LibWhacker
Two parts hydrogen and one part oxygen?
24 posted on 03/07/2004 5:33:03 AM PST by DCPatriot
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To: Joe Boucher
Oddly enough, there are SOME who say the flood was not just an event that happened here on the earth, but was a literal cataclysm...I am not even pretending to understand this theory, nor do I back it, so don't flame me guys...maybe a side effect of a comet swarm hitting the earth was the fact that Mars was in the way...I do find it rather odd that the photos of Phobos and Deimos are quite similar to the photo we had earlier this year of the nucleus of a comet.
25 posted on 03/07/2004 5:36:03 AM PST by Preech1 (There is one God and one mediator between God and men, the man Christ Jesus.)
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To: LibWhacker
"Venus, Mercury and Mars, the other approximately Earth-sized planets, likely suffered similar collisions around the same time. (How convenient) Comets were formed farther out from the sun than Earth, but in such abundance that they also rained down in the early solar system.

There you go, public school in; junk science out.

26 posted on 03/07/2004 5:43:00 AM PST by patriot_wes
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To: LibWhacker
It cost NASA $1B to prove what could be concluded from a good telescope photo.

Personally, I am all for reaching beyond the limits of Earth. We will do it of course, whether I like it or not. Our pioneering spirit is instinctual, and necessary to our survival. We will continue to spread our seeds as far and wide as possible.

NASA just isn't the answere. We should invest our exploration dollars in private enterprises, offering grants and rewards for specified achievments. Safety would improve, the ins companies would see to it. Obstacles would be quickly overcome, as companies raced to reach their goals.

Companies might also supplement their govt payroll thru commercial advertising. I have no problem with a "McOrbiter"...thats where you go before transferring down to the "Wrigglies" Bubble Dome, and entering the "Phillip Morris" Decontamination Chambers (Which would also be the only place under the dome that smoking is permitted.)

27 posted on 03/07/2004 5:46:41 AM PST by NeonKnight
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To: LibWhacker
Where did the water come from? "The only reasonable answer is comets."

So then, where did the water in the comets come from?

28 posted on 03/07/2004 5:52:44 AM PST by norwaypinesavage
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To: LibWhacker
What causes free hydrogen and free oxygen to combine to make water in the first place?

29 posted on 03/07/2004 6:05:56 AM PST by William Terrell (Individuals can exist without government but government can't exist without individuals.)
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To: Crazieman
Easy. The Bush administration destroyed the martian atmosphere and used all the water.

I think you're onto something. I bet Halliburton was involved - Cheney is lining his pockets!

NO BLOOD FOR MARTIAN WATER!!!

</sarcasm

30 posted on 03/07/2004 6:49:44 AM PST by Condor51 ("Diplomacy without arms is like music without instruments." -- Frederick the Great)
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To: norwaypinesavage; LibWhacker
So then, where did the water in the comets come from?

My question, exactly!
31 posted on 03/07/2004 7:29:06 AM PST by MaryFromMichigan (Insanity isn't so bad, once you get used to it)
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To: William Terrell; Tooters
>>>What causes free hydrogen and free oxygen to combine to make water in the first place?

Heat. In the case of the our emerging solar system, heat from the coalescing solar nebula. Something (radiation pressure from the young Sun?) shoved water and dust far away, out into the realm of the Oort Cloud where comets are believed to abound. Occasionally something disturbs the cloud (nearby passage of another star, some theorize) and sends comets towards the inner solar system.
32 posted on 03/07/2004 8:33:55 AM PST by ngc6656 (Freepaholics Anonymous advisory: Don't freep and drive.)
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To: ngc6656
Thanks for the quick response, ngc6656.
Do you have time for one more question?
I heard there was a movie called "Mars Needs Women".
Is that true?
Does Mars need women?
If so, why?

33 posted on 03/07/2004 8:41:38 AM PST by MaryFromMichigan (Insanity isn't so bad, once you get used to it)
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To: Arthur McGowan
So if the earth had been just a little closer or farther from the sun, no people. If we had been hit by just a few more comets, no dry land, and no people. Hmmm.

IMO, Authur, it would have required more than a few more comets. But you have hit on how critical small changes in distances (on an astronomical scale) are to the question of the existance of life as we know it in any planetary system.

34 posted on 03/07/2004 8:45:05 AM PST by ngc6656 (Freepaholics Anonymous advisory: Don't freep and drive.)
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To: Tooters
I heard there was a movie called "Mars Needs Women". Is that true? Does Mars need women? If so, why?

Why am I sitting here laughing, is this a trick question? ;>)

I do not know the answer. If you do, please share it with us!

35 posted on 03/07/2004 8:50:42 AM PST by ngc6656 (Freepaholics Anonymous advisory: Don't freep and drive.)
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To: LibWhacker
Q: Where did the water on Mars come from?

A: Where did the water on Earth come from?

36 posted on 03/07/2004 8:51:53 AM PST by Bloody Sam Roberts (If you can read this...you're too close.)
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To: LibWhacker
So, where did the water on Mars come from?

There are theories......

37 posted on 03/07/2004 9:00:49 AM PST by uglybiker (Evil Overlord Rule #86: Don't turn into a snake. It never helps.)
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To: ngc6656
Heat combines free hydrogen and free oxygen, and electricity separates them? Has anybody combined the two elements into water using artificial heat?

38 posted on 03/07/2004 9:32:57 AM PST by William Terrell (Individuals can exist without government but government can't exist without individuals.)
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To: William Terrell
Has anybody combined the two elements into water using artificial heat?

Many times in high school chemistry and physics classes, I would guess.

39 posted on 03/07/2004 9:49:51 AM PST by ngc6656 (Freepaholics Anonymous advisory: Don't freep and drive.)
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To: LibWhacker
For that to be the case, earth's temperature would have to have been too high to allow liquid water except at the poles.
40 posted on 03/07/2004 10:06:42 AM PST by Old Professer
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To: William Terrell
Lonely electrons.
41 posted on 03/07/2004 10:09:12 AM PST by Old Professer
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To: Old Professer
Lonely electrons.

Oh. Then they don't need heat, just Neil Clark Warren.

42 posted on 03/07/2004 11:03:13 AM PST by William Terrell (Individuals can exist without government but government can't exist without individuals.)
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To: ngc6656
There's name for that conundrum: How, if conditions had been just a little different, we wouldn't be here, in which case, we wouldn't even be here to marvel at how we managed to beat the astronomical odds.
43 posted on 03/07/2004 12:27:59 PM PST by Arthur McGowan
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To: governsleastgovernsbest
Here's an article I found on AskJeeves that answers some of your questions. It has always seemed to me that light compounds, and light elements not bound up in other compounds, particularly water, hydrogen and oxygen, etc., would boil off any giant ball of molten rock like early earth. So these things must've come from planetesimals, meteors, and comets that crashed into earth after it cooled somewhat, right? Unfortunately, that's as far as I could get in my role as armchair planetary scientist, so I'd have give it up and don my hat as, say, armchair general, and annoy a whole different group people, lol!

Anyway, here's that article. It's kind of long but there's some good stuff in it:

Water for the rock; did Earth's oceans come from the heavens?(research into the origin of the Earth's seas)

Science News, March 23, 2002, by Ben Harder

More than 4.5 billion years ago, the sun and its planets were taking shape from a rotating disk of ice, gas, and dust. This protosolar nebula was hotter and denser toward its center and cooler and less dense farther out. These gradients profoundly influenced the chemical composition of different regions of the early solar system, including the distribution of water. Close to the nebula's center, high temperatures and pressures vaporized ice crystals and the light elements and compounds called volatiles. The action blew these materials toward the outskirts of the nebula, leaving mainly grains of rock behind to form the inner planets.

Farther out, debris coalesced in meteorites called carbonaceous chondrites, which carry up to 10 percent of their mass in ice, The giant outer planets, such as Saturn and Jupiter, that arose in this neighborhood also contain some ice. Beyond these planets, water condensed in large quantities and formed comets, which are about half ice.

Compared with these icy objects, Earth contains little water. Only about 0.02 percent of its mass is in its oceans, and somewhat more water sits beneath the surface. Nevertheless, Earth has substantially more water than scientists would expect to find at a mere 93 million miles from the sun. How did Earth come to possess its seas?

Over the years, planetary scientists have proposed several possible answers to that question, but until recently they've had little data for testing their hypotheses. As research in the field progresses, however, the picture is getting more complicated--not less.

Analyses of the geochemical properties of various bodies in the solar system and computer modeling of the dynamics of ancient planetary interactions have undermined a formerly popular theory, which attributes Earth's water to a bombardment by comets late in the planet's formation.

New hypotheses are emerging as that theory's plausibility fades, and planetary scientists are struggling to reconcile data with these alternative scenarios. There's one thing on which most geochemists and astronomers agree: The celestial pantry is now empty of a key ingredient in the recipe for Earth.

JUST ADD WATER Because comets contain a greater proportion of water than other known celestial objects do, they make natural candidates as a source of Earth's rivers, lakes, and oceans. The distribution of hydrogen and water beneath Earth's surface suggests to many geochemists that water hasn't mixed deep into the planet, so they thought that the cometary bombardment applied a veneer of water to the dry planet relatively late in its formative period.

One attraction of this late-veneer scenario has been that it fits well with the early movements of planets and the many comets in the outer solar system, says Armand H. Delsemme, an astrophysicist now retired from the University of Toledo in Ohio. As Jupiter formed, its growing gravitational tug would have sent many icy comets hurtling from the range of the giant planets to all reaches of the solar system.

Over a billion years, at least hundreds of millions of comets collided with Earth, Delsemme says. The bombardment would have been especially heavy just after Earth formed.

Attributing water on Earth to these latecomer comets neatly explains a couple of things: first, how water that originated at the outer edges of the solar system got to at least one of its inner planets, and second, how water arrived late enough in Earth's formation for the planet to have sufficient gravity to retain it.

"The front-runner [hypothesis] until about 5 years ago was that water came from comets and came in late," says Kevin Righter, a planetary geochemist at the University of Arizona in Tucson. "One group of measurements changed that."

Those measurements were spectral analyses of the chemical compositions of three comets--Halley, Hyakutake, and Hale-Bopp--during near-Earth passes they made in 1986, 1996, and 1997, respectively. These analyses, the first that examined the hydrogen in water on bodies from a remote region, revealed a crucial chemical difference between the hydrogen in cometary ice and that in Earth's water.

Most hydrogen atoms possess a nucleus made up of a sole proton. Rarer forms also contain a neutron or two. The one-proton--one-neutron version, called deuterium, behaves chemically like hydrogen and can form water and other compounds. However, the resulting molecules are distinctly heavier than those containing the more common form, or isotope, of hydrogen.

Deuterium is exceedingly rare on Earth. Barely one such isotope exists for every 7,000 atoms of standard hydrogen. In contrast, the deuterium-to-hydrogen ratios in the three comets, according to the new observations, were all twice that in Earth's water.

The discovery gave researchers some pause. Assuming that the compositions of Halley, Hyakutake, and Hale-Bopp are representative of all comets, explaining how a hail of the objects could produce oceans with an earthly deuterium-to-hydrogen ratio is like trying to make a low-fat dessert from heavy cream.

According to the new data, cometary bombardment could account for no more than half of Earth's inventory of water, says Francois Robert, a geochemist at the Museum of Natural History in Paris and one of several researchers who brought the paradox of the incompatible ratios to light.

Such numbers might still fit a revised version of the late-veneer theory, says Leonid M. Ozernoy of George Mason University in Fairfax, Va. In addition to comets, asteroid-size planetesimals containing water with less deuterium could have contributed to the late veneer, says Ozernoy.

Smaller versions of these meteorites, the carbonaceous chondrites, hit Earth today in modest numbers. According to a computer model Ozernoy and his George Mason University colleague Sergei Ipatov have built, greater quantities and larger chunks of such material could have showered Earth toward the end of its formation.

Ozernoy and Ipatov have estimated the number of planetesimals that were flung at the early Earth from reservoirs of such bodies following orbits inside Jupiter's path or crossing it. These planetesimals could have delivered much of Earth's water, Ozernoy argued in January at the American Astronomical Society meeting in Washington, D.C.

WET BIRTH Adding wet planetesimals to the equation of Earth's early years puts a different face on the late-veneer theory, but it still doesn't satisfy many of the geochemical constraints that have been recently described, says Tobias C. Owen of the University of Hawaii in Honolulu.

Water isn't the only matter on our planet today that seems unlikely to have formed at Earth's proximity to the sun. There are also compounds and elements that readily vaporize, including chemically inert noble gases, such as argon, krypton, and xenon, and the elements nitrogen, oxygen, and hydrogen.

The ratio of xenon to krypton differs between Earth's atmosphere and typical carbonaceous chondrites today. By the same token, the argon-to-water ratios are dissimilar. Therefore, these wet meteors' larger kin, the planetesimals, probably didn't provide a veneer of material for Earth, Owen's analysis suggests.

The isotope profiles of nitrogen and oxygen on meteorites and Earth also argue against these bodies providing much of a wet veneer.

Michael J. Drake of the University of Arizona, who works with Righter, agrees that a late veneer didn't provide Earth's water. While he and Righter don't dispute that a veneer accounts for some of Earth's material, it couldn't have been wet. Certain metals, such as osmium, would have been pulled into Earth's central core if they had been present before the planet got wet. Therefore, all osmium in Earth's upper layers must have come in as a late veneer.

Drake and Righter have determined that the isotope profile of near-surface osmium closely matches that in ordinary chondrites--a type of meteorite that's bone-dry. And since carbonaceous chonidrites don't have the right proportion of osmium isotopes, they couldn't have made a substantial contribution to the late veneer, the researchers note in the March 7 Nature.

Taken together with the signatures of volatiles on Earth, these data suggest that no more than 50 percent, and probably less than 15 percent, of Earth's water could have been added from space at the end of our planet's formation, says Drake.

If existing objects in space couldn't have combined to make Earth's unique mix of water and other elements, the planet must have formed from--and entirely depleted--an ancient supply of water-rich material that has no modern analog, Drake and Righter argue. Because their hypothesis requires that Earth arose from water-containing materials already present in the inner solar system, it's called the wet-accretion hypothesis.

"Most of Earth's water has an indigenous origin," says Drake. The most probable source is a water-containing inner solar system reservoir at about the same distance away from the sun as Earth is now.

In the wet-accretion hypothesis, Earth developed from silicate rocks with water trapped inside. This hydrous material coalesced with other objects occupying the same swath of space. In their Nature report, Drake and Righter suggest that the band of the solar nebula was cooler than the temperature other researchers have inferred, thus allowing water ice to condense and become bound to the silicates.

ONE BIG SPLASH The role of chance in the solar system's evolution represents a wildcard that could trump both the late-veneer and wet-accretion models. Or it could fold for lack of hard evidence.

Allessandro Morbidelli of the Observatory of the C6te d'Azur in Nice, France, accepts Drake and Righter's hypothesis that Earth formed wet. However, he doubts that the planet evolved solely from material within a tight band at a specific distance from the sun, as the Arizona researchers envision. Their scenario isn't consistent with computer simulations of planetary formation, he says.

Morbidelli returns to the notion that bodies from the outer solar system brought water and volatiles to the inner solar system, but he hypothesizes that they made their contribution as the planets were forming rather than late in planetary development. If water came from millions of comets or small asteroids, the same steady celestial rain would have bombarded Mercury, Venus, Earth, and Mars, so they would all have begun with the same water characteristics, he says. However, the waters of those four planets now have dissimilar profiles, Owen and other geochemists have found.

If, on the other hand, a relatively small number of planetary building blocks brought water into the inner solar system, chance would dictate whether any one of them glommed onto an embryonic planet. A chance encounter--literally an accident in space-could have essentially flooded a planet in one big splash, but according to the luck of the draw, other planets could have spared. This could explain the current planets' differences in water content and why no existing objects appear to have been in the recipe for Earth.

To carry so much water, the impactor that doused Earth must have come from between Mars and Jupiter, Morbidelli says. Computer models that he and his colleagues described in the Oct. 1, 2001 Icarus show how this might have happened.

The researchers began with the premise that early in the solar system's formation, scores of planetary embryos about the size of Earth's moon were scattered around the sun to a distance four times that between Earth and the sun now (4 AU). The embryos' gravitational interactions with each other and with a growing Jupiter would have caused their orbits to begin crossing.

Some of these bodies would have collided with each other, building into ever-larger embryonic planets. Eventually, the researchers' simulations show, "out of a hundred or more embryos, just a few terrestrial planets form between 0.5 and 2 AU" from the sun, says Morbidelli. Each planet's unique mix of building blocks includes some embryos from outside its final orbit. In some cases, one or more embryos hail from far enough out that they would have been wet.

The weak point in Morbidelli's model is that there's no way to test whether a chance water delivery occurred in the case of Earth, Drake says. The carrier's elemental and isotopic characteristics would have to have been unlike those of any object that researchers have yet found in the solar system. "You can't rule out a [planetary building block] crashing in at 4.5 billion years ago, but it ... doesn't seem geochemically plausible," he says.

Only more data, especially more information about the amount and composition of water on Mars, will resolve the mysterious history of the inner solar system's water, says Jonathan I. Lunine, a planetary scientist at the University of Arizona in Tucson. Earth got its water locally--as Drake and Righter suggest--"then Mars [too] should have been swimming in water," Lunine says.

Preliminary data from the Mars Global Surveyor mission suggest that the Red Planet has large deposits of water (SN: 3/7/02, p. 149). Further analysis of Mars could indicate how much water the inner planets received from common sources, such as comets and meteorites. It could also help scientists characterize the sources of the remainder of Earth's original water budget.

Scientists are also counting on data from future comet encounters. Contour, an unmanned NASA probe scheduled for launch in July, will rendezvous with at least two poorly studied comets. It will pass Encke in November 2003 and then Schwassmann-Wachmann 3 in June 2006. Then, NASA may park the probe in a distant orbit to observe any other comets that come by. Data from the close encounters will give scientists better information on the noble gases in comets and could indicate how much cometary material ended up on Earth.

If any comets are found to have Earthlike deuterium-hydrogen ratios, they could add power to the late-veneer theory. Delsemme maintains that the comets responsible for the late veneer formed closer to the sun than the bulk of those left today--and thus had unique isotopic signatures. If he's right, then perhaps our oceans aren't a product of a rare celestial accident after all.


44 posted on 03/07/2004 1:33:51 PM PST by LibWhacker
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To: William Terrell
The Hindenberg, Lakehurst N.J. was a notable example....although speculation still exists that the igniting phenomenon was natural.
45 posted on 03/07/2004 4:02:29 PM PST by Smokin' Joe (As the oldest generation dies, the memory of liberty fades into obscurity, replaced by an impostor)
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To: William Terrell
Has anybody combined the two elements into water using artificial heat?

Yes. I did it in chemistry class . . . "burning" hydrogen produces water. It is an "exothermic reaction". Oxygen and hydrogen give up energy when combined and achieve a more stable state in combination than either "enjoys" in their elemental state.

46 posted on 03/07/2004 4:07:06 PM PST by Phil V.
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To: zeugma; xm177e2; XBob; whizzer; wirestripper; whattajoke; vp_cal; VOR78; Virginia-American; ...



If you'd like to be on or off this MARS ping list please FRail me

47 posted on 03/07/2004 4:10:15 PM PST by Phil V.
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To: LibWhacker; Liz; Howlin; ALOHA RONNIE; RonDog
But where did the water come from?

According to the latest Pepsi commercial, martians just ran off with the lander's wheels. Why not ask them?

48 posted on 03/07/2004 4:11:28 PM PST by Libloather (Will RATs ever learn? All I can do is hope not...)
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To: Phil V.
If you'd like to be on or off this MARS ping list please FRail me.

You take requests from outer space?

49 posted on 03/07/2004 4:13:00 PM PST by Libloather (Will RATs ever learn? All I can do is hope not...)
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To: Libloather
You take requests from outer space?

Depends.

What ya been smokein'?

Do you share?

50 posted on 03/07/2004 4:20:37 PM PST by Phil V.
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