Mars was formed around the time Earth was, but it was blessed with only 11% of Earth's mass and less than 40% of Earth's gravity field. Shortly after cooling solid, its "Noachian Era" was similar to proto-earth: warm, a thick atmosphere, plenty of liquid water on the surface, and probably a significant magnetic field.
But this era was still during the era of the Late Heavy Bombardment, a time in which the last dregs of the solar system were still settling out. Large asteroids still pounded the planets with regularity.
Unlike Earth, Mars had trouble maintaining its liquid iron magnetic field. Since it's much smaller, it cooled and thus congealed faster. And there's growing evidence that asteroid impacts were able to drive enough heat beneath the surface that interior convection was quelled, leading to a fragmented magnetic field.
Without an adequate magnetic field to deflect solar wind, the atmosphere was prone to shedding off pieces of itself into space. This was amplified by the lower gravity which meant holding on to lightweight gasses was even harder.
Over time, Mars cooled to the point where the major forms of tectonics ceased. The water locked up beneath the ground, rusted out pulverized basalt dust from the asteroid impacts, and frizzled in the radiation-baked atmosphere, floating off.
The seas and lakes dried, the rain stopped, and that... was that.
Three billion years later, we arrive on the scene and find out we have a little sibling. Then we send robots. We hope to find life, or evidence that it once lived. Characterizing how water worked in the Martian past is a part of answering that question.
> The seas and lakes dried, the rain stopped, and that... was that.
We think there was water on mars, therefore it is true. Is it too much to put a disclaimer somewhere that explains this is the current consensus but we have more to learn? The truth is that this story is riddled with assumptions, and readers need to know that.
So: "A positive correlation was found between X and Y"--why are you even telling me? What's the message? "There is evidence that X might cause Y"--okay, how strong is this evidence? Is it enough to care? "X probably causes Y"--that is what you're really trying to say. I will hear that and put it though my own Bayesian updating to give slightly more credence to the statement that X causes Y (more or less depending on the trustworthiness of the source, where I read it, what other supporting statements were made, etc.) The previous two forms don't change this mental process one bit, except to make it harder to dig out the thing you were actually trying to get across.
The nugget of truth in your statement is that some assumptions we are more sure of than others. We can probably say how old Mars is with more certainty than how much water there was on there. That may or may not need to be clarified, depending on what the focus of the conversation is.
There's a time and place for them. I don't think this was it.
When you react to something like this are your saying "I don't like narratives being presented to me like this. or "I don't want narratives being presented to people dumber than me like this."?
Major: 96.5% Carbon Dioxide (CO2), 3.5% Nitrogen (N2)
Minor (ppm): Sulfur Dioxide (SO2) - 150; Argon (Ar) - 70; Water (H2O) - 20;
Carbon Monoxide (CO) - 17; Helium (He) - 12; Neon (Ne) - 7
The best thinking right now is that Earth outgassed and held on to a similar volume of gasses as Venus. But since we had a substantial volume of liquid water on the surface, the oceans naturally absorbed CO2 and then deposited it on the sea bottom as carbonate minerals. (Life eventually learned that trick too, leading to things like shells)
So limestone, dolostone, chalks, calcite, marble, etc.... all those carbonates are likely the product of our liquid water oceans drawing out the vast bulk of the C02 in our atmosphere, leaving relict gasses in its place. Same starting point but we ended up with vastly lower pressure and vastly different final composition.
Venus had no such luck. She suffocates forever.
http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.htm...
http://spacemonitor.blogspot.com/2007/05/floating-city-on-ve...
http://www.flickr.com/photos/europeanspaceagency/3694512868/
I'm not sure if Mars suffers impacts from it, but impacts from sources such as the Oort Cloud (http://en.wikipedia.org/wiki/Oort_cloud) often contain ice and other materials. There are other examples if you search around.
The universe is a big and crazy thing, the possibilities of what can and have happened are almost endless.
An article from 2007 on the debate : http://www.newscientist.com/article/dn12026-mars-rover-finds... there are still some that believe at 'just the right time and place' you could get liquid water on the surface, but everyone seems to think it would be short lived.
Check the lat/long co-ordinates.
My mind is teeming with excitement of the possibilities, is anyone else as excited as me?
If traces of life are found, however distant in the past, it seems quite likely that any Mars colony or even exploration would be delayed by decades, if not longer. Preservationists would be against any interaction whatsoever.
If it's not sentient, it doesn't have a moral claim to the planet.
It would also be fun to discover that in its first billion years of existence as a wet planet Mars supported life in one form or another, simply to give us a data point in the probability function.
Imagine what that would do to culture, mythology, technological development...
Earth has a hot, churning, iron core and therefore still has a strong magnetic field to protect our atmosphere from the solar wind. Mars cooled long ago and its magnetic field weakened.
The story of Mars in short: flop planet, can't hydrosphere.
There is extremely strong evidence that in the very early years Mars was capable of holding on to a great deal of water: Enough to cover the Southern Hemisphere. The streambed seen here is from that time.
That downer is that this was over 3 billion years ago. Through a variety of processes and for a number of reasons most of Mars' water was lost to space or trapped underground.
The billion-dollar question that would be epic to answer: Did Mars develop Or acquire life during the time it had liquid water on the surface and if so is there any trace of it left, alive or dead?
From the article, "... This is the first time we're actually seeing water-transported gravel on Mars. This is a transition from speculation about the size of streambed material to direct observation of it ..."
What's cool about that is that it allows you to directly calculate how much water flow was involved in moving this gravel (taking in to account the much lower Martian gravity), you can use the pattern in which the gravel deposited itself to determine what direction the flow was going, and more.
Why isn't this front page, the implications are staggering.
Good point. The theory of a flowing river should support all types of evidence at large & small scale: alluvial fans,
"... The imagery shows an alluvial fan of material washed down from the rim, streaked by many apparent channels, sitting uphill of the new finds. ..."
to pebbles and rate of flow of liquids,
"... From the size of gravels it carried, we can interpret the water was moving about 3 feet per second, with a depth somewhere between ankle and hip deep... This is the first time we're actually seeing water-transported gravel on Mars. This is a transition from speculation about the size of streambed material to direct observation of it. ..."
All directly observable evidence, each piece confirming the conclusion.
Water has always been supposed to have played a role in the state of Gale Crater, and it must have been moving water at some point...
Also, if there was ever a significant amount of organic matter in that stream, we may be able to find out about it through the SAM instrument. It turns out someone was planning ahead and shipped a gas chromatagraph with a mass spectrometer and laser spectrometer attached. You know, just in case we wanted to pick up some dirt and figure out what the heck sort of complex chemicals are in it. Which we do!
Out of interest, how do we know it was water, and not some other liquid?
Furthermore, most liquids found at reasonable temperatures aren't all that voluminous, and a number of the minerals scanned and inspected on Mars show evidence of water contact.
Basically, there's not much else it could be. :) That said there's some really cool theorizing on underground carbon dioxide flows that might explain some washouts seen later in Mars's life.
you mean these? "small spherical hematite balls, dubbed ‘blueberries,’" ~ http://www.lifescientist.com.au/article/436306/iron_blueberr... Goethite: learn something new every day.
The cemented section on the mars side is in itself most interesting I find and yet seem unable to state why. Wonderous stuff indeed.
It's tiresome hearing of the "piling evidence" for water on Mars. Find some damn water. Prove it by melting it then boiling it on camera in a container with a thermometer.