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.
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Terence Dickinson is editor of Skynews magazine and author of books for backyard astronomers.
I don't recall reading anywhere that God proposed comets as the source of planetary water, but because it is a marvelous idea it is within the realm of possibility.
Ancient civilizations generating electricity on Mars. They used the Earth as a dumping ground for the toxic Dihydroxide waste.
The draconian environmental policies of the Bush Administration.
No wait.....Is water a good thing?
IIRC he had a telescope that scanned the sky in UV. He noticed black dots that appeared against the background and then disappeared. He interpreted these as large "snowballs" that were continuously entering the upper atmosphere and melting. (Water absorbs UV). The problem was that the dots he was seeing were never larger than 1 pixel. Critics claimed he was just seeing noise from his detector. Frank planned to build a build a better system, but I never heard what happened after this.
Lake Steadman
Geometry
Latitude 24.65°
Longitude 207.10°
Poland Spring?
Hey, it was worth every cent I charged for it.
My own pet theory is that most of it is here.
"And the problem with sufficient atmosphere is that Mars is not large enough to have enough gravity to hold a respectable atmosphere in place. Which, to me, points to the idea that Mars was once larger than it is now."
I submit another possibility. Mars' core was once liquid, which would mean that Mars at once had a magnetic field. Such a magnetic field would keep the solar wind from abrading away the atmosphere. Look at sketches of Earth's magnetic field in relation to the solar wind, and such sketches show a bow shock wave. The charged particles of the solar wind are deflected by the magnetic field. Now granted the solar wind is not very dense, but going on the order of a million miles per hour it does things like throw space probe trajectories off a bit (measureable) and over time (geologic scales mind you) can have some significant impact.
When the iron core of Mars solidified, the field was lost, no bow schock to shield the atmosphere.
Damn! Now I need to go to the bathroom.
I didn't know there was water on Mars.
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