Cold, yes, but as a youth I knew some hotties there.
Posted on 07/21/2005 1:57:09 PM PDT by LibWhacker
A chemical study of Martian meteorites implies that the planet has always been cold and was rarely above freezing.
Writing in Science, researchers have been able to determine the maximum temperature the rock experienced.
There is no evidence that it was ever warm, they say, as it records near surface conditions for four billion years.
The water erosional features seen on Mars must have been made during very brief periods, they conclude.
Thermal history
Although the current average temperature at the Martian equator is about minus 55 Celsius, many scientists believe that the Red Planet was once warm enough for water to have existed on its surface, and for life to possibly have evolved.
There is plentiful evidence that water has flowed on the surface. They include deep canyons, dried up river beds and many examples of deposits left behind by running water.
But the recent analysis, by David Shuster of the California Institute of Technology and Benjamin Weiss of the Berkeley Geochronology Center, of meteorites blasted from Mars seems to paint a different picture.
The new work involves two of the seven known "nakhlite" meteorites (named after El Nakhla, Egypt, where the first such meteorite was found), and the celebrated ALH84001 meteorite that some scientists believe shows evidence of past microbial activity on Mars.
Using geochemical analysis techniques the researchers reconstructed a "thermal history" for each of the meteorites to estimate the maximum long-term average temperatures to which they were subjected.
"We looked at meteorites in two ways," says Weiss. "First, we evaluated what the meteorites could have experienced during ejection from Mars, 11 to 15 million years ago."
Their conclusions were that ALH84001 could never have been heated to a temperature higher than 350 Celsius for even a brief period of time during the last 15 million years.
The nakhlites, which also show very little evidence of shock-damage, were unlikely to have been above the boiling point of water during their ejection from Mars 11 million years ago.
'Leaking' Argon
The other part of the research addressed the long-term thermal history of the rocks while they resided on Mars. The scientists did this by estimating the total amount of argon still remaining in the samples.
The gas argon is present in the meteorites as well as in many rocks on Earth as a consequence of the radioactive decay of potassium. A noble gas, argon is not very chemically reactive, and because the decay rate is precisely known it can be used to date rocks.
However, argon is also known to leak out of rocks at a temperature-dependent rate. The cooler the rock has been, the more argon will have been retained.
The researchers found that only a tiny fraction of the argon that was originally produced in the meteorite samples has been lost through the aeons suggesting that the Martian surface has been in deep-freeze for most of the last four billion years.
"The small amount of argon loss that has apparently taken place in these meteorites is remarkable. Any way we look at it, these rocks have been cold for a very long time," says Shuster.
"The ALH84001 meteorite, in fact, couldn't have been above freezing for more than a million years during the last 3.5 billion years of history."
Water, water, everywhere?
This new line of research is a puzzle given the contrary evidence of running water on Mars.
"Our research doesn't mean that there weren't pockets of isolated water in geothermal springs for long periods of time, but suggests instead that there haven't been large areas of free-standing water for four billion years," says Shuster.
"Our results seem to imply that surface features indicating the presence and flow of liquid water formed over relatively short time periods."
In fact, the evidence shows that during the last four billion years, Mars has likely never been sufficiently warm for liquid water to have flowed on the surface for extended periods of time.
This implies that Mars has probably never had a hospitable environment for life to have evolved, unless biology got started started during the first half-billion years of its existence, when the planet was probably warmer.
The study is bound to be controversial showing a disparity between those scientists who look at pictures of Mars to discern its history and those who study the only pieces of the planet we can examine in detail in the laboratory.
Wow! Sounds like their "Kyoto Treaty" really worked!
Wouldn't be at all surprised to learn that most of that warmth came during the period when the martian volcanoes were active. If the planet was always cold, then it would follow that a pretty good portion of the water it had is still there. Except for the stuff evaporated by the volcanoes, the only way it could lose water would be through sublimation of the ice on the planet's surface, and since much of the ice is subsurface, I would think that process would be pretty slow.
They heard this through the grapevine?
Cold, yes, but as a youth I knew some hotties there.
Some disparity; on the order of having a copy of Hustler or hiring a street walker.
Mars girls are easy?
Ah saying Mars has "always been cold and was rarely above freezing" based on a meteor sample "ejection from Mars, 11 to 15 million years ago."?..
By definition the meteor sample is only valid for data on Mars up till the time they were ejection from Mars...
you have a, 11 to 15 million years till now, data drop out there...
really puts a damper on making overall blanket assertion on the total Mars geo.history...don't you think?
OTOH, ten million years is only two or three one-thousandth of four billion years. So we have to be careful about saying it's not a representative look at Martian history... It'd be a little like saying we don't have a good understanding of American history if we don't know anything about the last six or seven months of it.
Ping
Mars has likely never been sufficiently warm for liquid water to have flowed on the surface for extended periods of time.
So the super giant canyon on mars was not made by erosion over a long period of time?
So if it was made in a relatively SHORT period of time,
where did that tremendous volume of water come from?
Where did it go?
It had to take a lot of fossil fuels to pre-position all of those machines for Spielberg's movie. What other explanation could there be?
Alas, not with me. < |:(~
That's horsepucky! It was only 3,894,216 years...
I have a very strong feeling that Mars is going to teach us a whole boatload of geological tricks that we've never seen on planet Earth!
Didn't the Elton John song "Rocket Man" say something about Mars not being a good place to raise your kids, in fact it's cold as hell?
Wow! I guess the "Mars Needs Women" problem is SOLVED!
I only have records for about 3 1/2 billion years (mostly Elvis and Beatles), so they may be right.
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