Post by Tulameen on Jun 10, 2005 11:03:46 GMT -5
Kinda makes you wonder what happened, doesn't it?
More Rivers Spotted on Mars
By Larry O'Hanlon, Discovery News
June 10, 2005 — Long-dead rivers have just had a population explosion in the dry valleys of Mars, according to a scientist at the Smithsonian Institution.
New data from orbiting Mars cameras have picked up evidence of 21 more rivers with flows once comparable to similar-sized rivers on Earth today. That makes 28 rivers, total, that may have once flowed on Mars.
Whether these were carved by single deluges, a few pulsed floods or a relatively brief rainy climate some 3.7 billion years ago remains a mystery.
"We were trying to determine how much water flowed through these valleys," said Smithsonian Institution Mars researcher Rossman Irwin. A report on the newfound rivers appears in the June issue of the journal Geology.
Even rough calculations of the water flow were almost meaningless in past years because the Mariner spacecraft imagery just wasn't good enough to peer into the bottoms of Mars' huge canyons and measure the actual channels in which water flowed, Irwin explained.
More recent data from the eagle-eyed Mars Odyssey spacecraft has provided that channel view — along with clues about smaller tributaries.
By mapping out the tributaries and main channels of the dry rivers, Irwin and his colleagues were able to define the boundaries of ancient watersheds and calculate the amount of water — perhaps as rain — it would have taken to create the channels.
"What you get is a centimeter (half-inch) of precipitation per day," said Irwin. That's a conservative number, he says, because there are a lot of unknowns — like how deep the rivers ran.
"We assumed they're fairly shallow," Irwin said, based on the shallow, meandering rivers found in desert areas on Earth.
It's also clear that whatever created the wet conditions, it ended abruptly about 3.6 billion years ago. Evidence for that is the fact that the ancient tributary and river channels still exist.
On a wet planet like Earth, such features would be quickly eroded away by rain and snow.
"What we are looking at is the evidence of the last flows on Mars," said Irwin. "The climate on Mars deteriorated very, very quickly."
Previous studies of Martian water drainage features have come to similar conclusions, said U.S. Geological Survey geologist Mike Carr, a prominent authority on Mars surface features.
"It looks like the Martian (drainage) systems are immature," said Carr. In other words, they were either cut quickly with large floods or slowly with very infrequent flows.
Either way, says Carr, they didn't have the water power to develop into the large, finely branched drainage patterns found in the Mississippi or the Amazon basins on Earth.
Nonetheless, "finding these (rivers) is comforting," said Carr.
The new waterways confirm what many scientists had suspected would be found at the bottoms of those Martian canyons, he said. It further supports the prevailing view that the Red Planet once had liquid water on its surface.
More Rivers Spotted on Mars
By Larry O'Hanlon, Discovery News
June 10, 2005 — Long-dead rivers have just had a population explosion in the dry valleys of Mars, according to a scientist at the Smithsonian Institution.
New data from orbiting Mars cameras have picked up evidence of 21 more rivers with flows once comparable to similar-sized rivers on Earth today. That makes 28 rivers, total, that may have once flowed on Mars.
Whether these were carved by single deluges, a few pulsed floods or a relatively brief rainy climate some 3.7 billion years ago remains a mystery.
"We were trying to determine how much water flowed through these valleys," said Smithsonian Institution Mars researcher Rossman Irwin. A report on the newfound rivers appears in the June issue of the journal Geology.
Even rough calculations of the water flow were almost meaningless in past years because the Mariner spacecraft imagery just wasn't good enough to peer into the bottoms of Mars' huge canyons and measure the actual channels in which water flowed, Irwin explained.
More recent data from the eagle-eyed Mars Odyssey spacecraft has provided that channel view — along with clues about smaller tributaries.
By mapping out the tributaries and main channels of the dry rivers, Irwin and his colleagues were able to define the boundaries of ancient watersheds and calculate the amount of water — perhaps as rain — it would have taken to create the channels.
"What you get is a centimeter (half-inch) of precipitation per day," said Irwin. That's a conservative number, he says, because there are a lot of unknowns — like how deep the rivers ran.
"We assumed they're fairly shallow," Irwin said, based on the shallow, meandering rivers found in desert areas on Earth.
It's also clear that whatever created the wet conditions, it ended abruptly about 3.6 billion years ago. Evidence for that is the fact that the ancient tributary and river channels still exist.
On a wet planet like Earth, such features would be quickly eroded away by rain and snow.
"What we are looking at is the evidence of the last flows on Mars," said Irwin. "The climate on Mars deteriorated very, very quickly."
Previous studies of Martian water drainage features have come to similar conclusions, said U.S. Geological Survey geologist Mike Carr, a prominent authority on Mars surface features.
"It looks like the Martian (drainage) systems are immature," said Carr. In other words, they were either cut quickly with large floods or slowly with very infrequent flows.
Either way, says Carr, they didn't have the water power to develop into the large, finely branched drainage patterns found in the Mississippi or the Amazon basins on Earth.
Nonetheless, "finding these (rivers) is comforting," said Carr.
The new waterways confirm what many scientists had suspected would be found at the bottoms of those Martian canyons, he said. It further supports the prevailing view that the Red Planet once had liquid water on its surface.