Mars Images Reveal Evidence of Ancient Lakes 128
Matt_dk writes "Spectacular satellite images suggest that Mars was warm enough to sustain lakes three billion years ago, a period that was previously thought to be too cold and arid to sustain water on the surface, according to research published today in the journal Geology. Earlier research had suggested that Mars had a warm and wet early history but that between 4 billion and 3.8 billion years ago, before the Hesperian Epoch, the planet lost most of its atmosphere and became cold and dry. In the new study, the researchers analysed detailed images from NASA’s Mars Reconnaissance Orbiter, which is currently circling the red planet, and concluded that there were later episodes where Mars experienced warm and wet periods."
Re:How do they determine those dates? (Score:3, Informative)
Wow, you seem terribly defensive over what is a pretty reasonable question. This is slashdot, you are allowed to ask things here...
Anyways, from what I understand (and this is in no way my field), they usually date these sorts of things by observing what kind of geological features are on top. If a crater has numerous smaller craters in it, then you know the larger crater is older. With the crater distribution they can make pretty reasonable estimates about the age of something. Similar methods techniques could use other forms of erosion.
Dating like this obviously isn't exact, and you'd have to ask a geologist for more details on the accuracy and techniques. For that matter, I haven't read TFA so I don't know that this is exactly how it was done. If you are really curious, I suggest you RTFA, and read any papers these scientists have/will release on their findings.
Re:How do they determine those dates? (Score:1, Informative)
The article does address this:
"The researchers determined the age of the lakes by counting crater impacts, a method originally developed by NASA scientists to determine the age of geological features on the moon. More craters around a geological feature indicate that an area is older than a region with fewer meteorite impacts. In the study, the scientists counted more than 35,000 crater impacts in the region around the lakes, and determined that the lakes formed approximately three billion years ago. The scientists are unsure how long the warm and wet periods lasted during the Hesperian epoch or how long the lakes sustained liquid water in them."
Re:How do they determine those dates? (Score:5, Informative)
The researchers determined the age of the lakes by counting crater impacts, a method originally developed by NASA scientists to determine the age of geological features on the moon. More craters around a geological feature indicate that an area is older than a region with fewer meteorite impacts. In the study, the scientists counted more than 35,000 crater impacts in the region around the lakes, and determined that the lakes formed approximately three billion years ago. The scientists are unsure how long the warm and wet periods lasted during the Hesperian epoch or how long the lakes sustained liquid water in them.
So to answer your question the moon is the reference point.
It has large error bars, but it's the best we have until we can send radiometric dating to these areas. [Crater Counting [wikipedia.org]]
Re:How do they determine those dates? (Score:5, Informative)
How are these dates determined?
Basically, they're counting craters.
The idea is that everything in the solar system is being steadily bombarded by random bits of debris. More craters means that something has been exposed to the elements for a longer amount of time.
In this case... If you have a once-lakebed that's now covered with craters, it must have been a while since there was water in it.
No, it isn't perfect. But it isn't too horrible either.
And, of course, the numbers will be refined as more/better data and measurements become available.
Re:Terraforming? (Score:3, Informative)
any effort to seed the martian atmosphere would at best be a temporary(ok, a few million years) improvement. Mars lacks the gravity to hold the atmosphere. what's more, the warmer the atmostphere the faster it will disipate off into space.
in the 3 billion years since the lakes existed, mars has reached an equilbrium.
Re:At the risk of being serious... (Score:3, Informative)
We could learn a lot from Europa because Europa has a small iron core which is heated by tidal friction, and under the the 3km of ice there may in fact be 100-200 kilometers of salt water . Now it is odd, that our space agencies, that claim to be searching for life willfully have ignored Europa other than a few flybys.
Maybe they're put off by that 3km of ice. How exactly are they going to drill through that ice, when the best we've managed so far with remote probes is to launch a few wheeled rovers to a dry planet very nearby, and even those have problems with broken wheels and getting stuck in sand. We're nowhere near the point where we can launch a probe that drills through 3km of ice and maneuvers around in whatever's below, and then manages to maintain communication through that 3km of ice.
Don't forget, our budget for space exploration is peanuts. Canceling the Mars missions isn't going to add enough to the budget to accomplish these missions you dream of, and we can't enlarge NASA's budget because we're too busy fighting oil wars and bailing out mismanaged private companies.
Yes, JFK said we should do the hard things. He didn't say we should do the impossible things. You have to walk before you can run.
Re:Why? (Score:4, Informative)
The limitations of our current robots were based on space, cost, and durability. A geologist might be able to search the terrain faster, but they won't be able to be there for more than a few days or weeks at best, and each geologist could really only search one general area. In the same space as your single geologist and all the food and resources he/she will need, we could explore multiple places on the surface of Mars with a generous handful of Spirit-type robots, and they could all stay there for years collecting data.
The reason Spirit and Opportunity are so slow is because they operate on a small solar array, that generates (at peak) 140 watts for the 4 hours of daylight they get in a Martian day. That's about 560 watt/hours an m-day at best, and that's all the energy they need to do what they do. That's a lot of science packed into that amount of energy. They are currently getting a fraction of that due to dust on the arrays, and yet they are still collecting good science, six years in.
If you want enough energy to support a human being there, you're talking nuclear engines. If you're going to make that kind of energy available, you might as well power the robots with nukes - they will then be able to move faster than a human could, and there could be hordes of them for the same cost and resources expended sending one human. And they could stay for years.
To get a single human to mars, on the surface, and back to Earth, you'll need about a half ton of dehydrated food, enough water to recycle so they have a continuous supply, and probably a few thousand watt-hours a day minimum for the entire trip for heat, light, etc. You'll also need radiation shielding (likely tons of it) for the multi-year trip, room for them to exercise, many tons of fuel for the two-way trip, etc.
Spirit weighs about 400 pounds, or a little over twice the weight of a human. But you save the half-ton of food, the water, more than half the fuel (no return trip, no need to re-orbit it), and almost all the energy needed to sustain life during the voyage. The ship is simpler, since you need almost no shielding, no living space - just strap a few (or a few hundred) robots around the outside of a rocket engine.
Take a science team of a dozen, and you could probably have at least 50, maybe 100 robots take their place. And those robots would be able to work there for years. Each could have its own nuclear plant and probably have power and functioning instruments for decades (energy starvation from the solar cells is what is slowly killing off the current robots).
Plus, robots can make a one-way trip. No need to store fuel to bring them all back, just enough for a few dozen of them to send a sample back to a central ship in orbit, which can then pack up the samples and send them back on a relatively small rocket that weighs a few hundred pounds.