Slashdot Mirror
Mars Had Surface Water for Eons
LukePieStalker writes "Far from being a one-time event, it now appears that surface water
flowed on Mars for eons. Nasa has announced that, after descending
down further into the Endurance crater, the Opportunity rover has found a 'razorback'. It is believed that this was formed by 'fracture fill' from the minerals in percolating water. Since this feature extends through several geologic layers, it argues for a long period of wetness near the surface. This would seem to substantially increase the chance that life once existed on the red planet."
Is water all that common?
Not only is water uncommon, the liquid phase is uncommon. Also, the reason it's so important is because it is less dense in the solid phase than the liquid phase, which allows it to freeze on top instead of on bottom, which in turn allows organisms to sustain life even when the body of water begins to freeze.
I are winner
Water should be pretty common near stars as Hydrogen is the fuel which runs them. When combined with oxygen pulled near the star by gravitation, you find yourself with water. The difficulty is in finding it in liquid form. Planets and planetoids near a star will have their water blown or boiled away. This water will then travel toward the outer system. If no large body exists in the star's "temperate zone", then the water will continue on. If it hits a body outside of the "temperate zone", it will remain as ice.
At least, that's how I understand it.
Javascript + Nintendo DSi = DSiCade
The longest division of geologic time, containing two or more eras. For example, an era where Mars had water and an era afterwards, where there was no water.
-Valiss
Because all those musings about we know this was probable and that is likely and blah blah will remain theoretical until evidence is found in support of them. That's the natural progression of science.
The darkness... controls the music. The music... controls the soul.
We know there's still water there; unfortunately, it's in the form of ice.
As for fossils or traces of life... who knows? All we can say is that Spirit and Opportunity aren't going to be finding it unless it's macroscopic. They can only dig centimeters deep, and don't have the sort of magnification needed to see microscopic organisms.
Windmills do not work that way!
"Not only is water uncommon, the liquid phase is uncommon"
That should have read:
"Water is not uncommon; only the liquid phase is."
Our solar system is jam packed full of ice. Heck, Uranus and Neptune are best described as "Ice Giants" instead of "Gas Giants", due to their expected ice cores. Ice dominates the moons in the saturnian system, the kupier belt and oort clouds are composed mostly of ice, etc, etc. In fact, it is even theorized that Earth got its water from comets.
Windmills do not work that way!
Erm, minor correction: Uranus and Neptune have ice mantles, not cores. Their cores are expected to be rock. Their atmospheres are relatively thin compared to the true "Gas Giants".
Windmills do not work that way!
Surface water on Mars existed across a significant span of time, not just for years but eons, suggest new findings made by NASA's Mars rover Opportunity.
Within a few weeks of its landing on Mars in January 2004, Opportunity revealed what was uppermost on the twin rovers' agenda: that bodies of liquid water once existed on the surface of Mars. But the evidence proved what could have been only a solitary event - a single wet episode.
The new discovery, reported by NASA's Jet Propulsion Laboratory on Friday, pushes the boundaries significantly further back, into geological timescales.
After motoring down several metres into a the large Endurance crater, Opportunity has found what science team member Jack Farmer of Arizona State University calls "razorback," a ridge of thin, jagged vertical plates sticking up at the edge of a flat expanse of bedrock.
The team suspects that the ridge is a layer of rock that formed when earlier layers of rock cracked, and mineral-laden water percolated through the cracks leaving deposits behind, forming veins, or "fracture fill". Those deposits formed rock harder than the surrounding material, so as the rock eroded away it left this harder ridge behind. The fractures, Farmer says, may have been caused by the impact that produced the crater.
Salt crystals
The surrounding rock is the very bedrock that Opportunity has been studying ever since its arrival on Mars, first in a tiny crater called Eagle, and for the last month in the much larger Endurance crater.
In both places, the layered bedrock has provided multiple lines of evidence - unusual minerals, voids left by dissolved salt crystals, and hematite spheres - showing that liquid water once flowed there. And at the Endurance site, this evidence for water extends through five successive geological layers, or units, extending back in time from the original layer.
But the new "razorback" find dramatically extends this record. Formation of such crack filling material requires liquid water, but at a time so much later that these different layers of marine sediment had time to be compacted into stone, hard enough to form sharp cracks rather than crumbling.
The actual time span has not been estimated, but it reveals enough time to strengthen the possibilities that life could have evolved on Mars. The team is expects to spend most of this week analysing the razorback with the rover's various spectrographs.
Dwindling sunlightMeanwhile, there was great excitement on the other side of Mars. The rover Spirit, skirting the edge of a hill called West Spur on the edge of Columbia Hills and preparing to drive up it, has now driven over an outcrop of bedrock - something that had never been seen before at Spirit's site in Gusev crater.
"Eureka! We have found it!" exclaimed Matt Golombek of NASA-JPL, a science team member. "Spirit has an outcrop under the rover wheels. And an outcrop is the currency for geologists." Studying it should help reveal the geological history of the Gusev site.
Both rovers are in the most scientifically interesting and technically challenging terrain yet, though both are also somewhat limited by the dwindling sunlight and plummeting temperatures as midwinter approaches in September. And both remain healthy, despite one balky wheel on Spirit, having more than doubled their 90-day design lifetimes.
Both Mars and Venus are bone dry because they have little to no magnetosphere. This allows water vapor to be broken into H and O by UV radiation and since the H is light, it can acheive escape velocity much faster when hit by unhindered solar wind.
Blaze a trail to the New World
Earth has a large moon which stabilizes the tilt angle of its rotation axis. The Earth bulges at at equator from its rotation and the pull of the moon. The moon pulling on this bulge keeps the earth's axis steepening much more than it is now- a 23-degree tilt. The tilt angle creates the seasons. If it tilted more, there'd be warmer summers and colder winters.
Mars lacks a significant moon. Therefore people speculate that it could tilt all the way over on its side sometimes and have extreme seasons. Maybe even extreme enough to melt the carbon and water ices at the poles and permafrost.
Ammonia is not stable in the Martian environment. Any ammonia present would break down. Therefore, if ammonia is found, it must be being regenerated by some process. The most common processes for generating ammonia are biological.
They already did that on Viking. The results were inconclusive, but suggestive of abiotic processes. The tests were as follows:
GEX (Gas EXchange experiment): Looked at gas level changes in martian soil vs. a control which it sterilized first.
LR (Labeled Release experiment): Looked for uptake of a radioactive liquid by gas presence, again vs. a control which it sterilized first
PR (Pyrolytic Release experiment): Like the LR, but in reverse; cooked the samples afterwards to see if they uptook radioactively tagged CO2.
GCMR (Gas Chromatograph - Mass spectRometer experiment): Heated soil samples and did a spectral analysis of them.
First, GCMR's results: Found an unexpected amount of ice, but found surprisingly *little* organics, leading scientists to conclude that some process was *destroying* organics on Mars.
For the others, the following would have been expected from each if there was life:
GEX, sample: O2 or CO2 released
GEX, control: No release
LR, sample: Labelled gas emitted
LR, control: No release
PR, sample: Carbon detected
PR, control: None
If there was no life, both samples and controls were expected to be the same. The real results?
GEX, sample: O2 released
GEX, control: O2 released
LR, sample: Labelled gas emitted
LR, control: No release
PR, sample: Carbon detected
PR, control: Carbon detected
In short, it was confusing, but was believed to be related to abiotic processes.
Windmills do not work that way!
At 1 atm pressure, ammonia melts at -108F, and boils at -28F (from GPSA handbook). So it has an 80F range of liquidity, whereas water has 212F. However, like you said, ammonia solid is more dense than the liquid. Water is one of only a very few materials (gallium is another, I can't remember any others but I bet there are some) that are more dense as a liquid.
By comparison, methane melts at -296F and boils at -259F.
Just your friendly neighborhood chemical engineer!
It all started with ths:
Read me
I'm sure they're having intermittent problems that will eventually get worked out over the coming days.
--
Does anyone remember
That's a common misconception promoted by creationists.
Only dating methods such as radiocarbon dating (which we couldn't even begin dreaming of doing on Mars yet without a lot more study) are calibrated, and even then, it's a pretty minimal calibration factor (which on Earth we determine through dendrochronology and sometimes ice cores).
Most radioisotope dating methods not only don't have calibration, but have built-in error checking, such as isochron and concordia-discordia methods.
Windmills do not work that way!
Why water? Many Sci Fi authors have predicted life cycles based on other substances, in various and other temperature gradients.
I think the main point here is that we know that life can grow where there is water, and we have some pretty good ideas what to look for. For instance, we are looking for proof of water on Mars, and then we know to look where the water USED to be in order to find where life MAY have been.
When it comes to life that isn't carbon based and/or came from water, we simply don't know what to look for. We could be looking right at it and not see it because we have no point of reference, no experience, no tell tale signs that say "life was/is here". That doesn't mean life doesn't exist without water (or without being carbon based). It just means we would be unlikely to understand what we found with the limited tools on a probe unless the think came up and started waving "hi" to us.
Considering that water is relatively common in the areas of the solar system that we would THINK there could be life (venus thru mars + moons of outer planets), the smartest investment we can make is to look for the kind of life we know can exist, where we think it can exist. This means where liquid water is or was.
Tequila: It's not just for breakfast anymore!
That would involve multiple lines of dendrochronology which conform with each other and with the conventional historical account to all be incorrect, but not only that, but all be incorrect by the same amount compared to different artifacts. Hardly a realistic proposition. It also would require a truly massive calibration factor. Lastly, it's only applicable to radiocarbon dating, which is hardly the only dating method used.
The only time when the calibration factors become large are concerning objects from the 1950s onwards; nuclear testing really screwed up atmospheric carbon ratios, and introduced a geographical component. However, it gave a new benefit: we can now better track rates of carbon movement on a global scale. Also, there are the cases when carbon dating is not supposed to be used (which Creationists often use, of course); for example, ocean-dwelling organisms (which ingest recycled conveyor carbon) and organisms that spent their lives within a few hundred feet of a volcanic vent (which get deep earth carbon in addition to atmospheric carbon). This is known as the "resevoir effect".
Windmills do not work that way!
Lately I've been having numerous page rendering errors, and I haven't changed my browser, so I'm basically assuming that they fucked up some part of slashcode and are casually working on repairing it.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
It's also worth noting that radiocarbon dating would be useless on Mars for two reasons: 1. It only works for formerly living material (all Terrestrial keeps the objective isotope of carbon around in a very specific ratio), and we have no confirmed fossils from Mars, and it would be a very long shot to count on finding them on a future mission. They'd be farther ahead just dating the rocks through other methods. 2. It's a relatively short-term dating (Creationists abuse this fact too, by pointing out that carbon dating on dinosaurs puts them right up to our geologic yesterday. The fact is, dinosaurs have been dead so long that all the carbon 14 in their remais is long since decayed beyond detectability). I forget the exact range, but as I remember, even going back as far as the KT boundry, it's already useless. If there was/is life on Mars, odds are most if not all of it has been dead for a very long time, and would again fall into the realm of more long-term dating methods. It would be more likely to produce good data if the probe relied on a dating method that could give results over a good chunk of the age of the solar system. On the off chance that we find something new enough to be interesting, I'd call that justification for a follow-up.
While this is probably true, we don't know this for sure yet.
Good point. So many 'scientists' claim that water is a requirement for life, but that may not be true. Any other liquid solvent may not be necessary. If an organism can get its energy and dispose of waste products without a solvent, it is not a requirement.
You are right. We just don't know this for sure.