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Mars Images Reveal Evidence of Ancient Lakes
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."
The images speak pretty clearly for themselves, and have done so for a long time. We already know since forever what formations liquid deposits create over time on malleable surfaces.
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]
Contrary to what the "internet" likes to tell you, many people question what scientists say because they want to see actual proof to support the claims rather than just additional layers of theories and educated "guesses".
And the people who are legitimately intellectually curious rather than simply delighting in taking jabs at the "scientific orthodoxy" don't universally phrase their questions as "Do you know what you're talking about or are you making shit up that supports your preconceived notions?"
"How do they determine those dates?" is a fine question, one I am curious about as well. "Gee, in the scientific method I'm used to, you have to have a known reference. Do they have one? Have they been following the scientific method?" kinda makes you sound like the kind of person you are implying you aren't. Maybe you're just being defensive, or using modding reverse-psychology. But really, just leave that part out.
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Continuing off topic...
Your post reminds me of the day a coworker came into my office with a look of deep thought on her face, asking why we need to use money. Not getting where she was going, I started explaining that money is just an accounting system. That didn't satisfy her, so I started to explain how it evolved from barter.
She stopped me, and saying that she understood that, followed by a but "Why can't we just go to work, and when we need something just go to the store and get it? Why do we need to keep track of it with money? That's what I think we should do."
At that point I got what she meant, and told her that theoretically we could. And said "What you are describing is communism." She then puffed up and angrily said "YOU are a communist." and stomped out.
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.
"Work is the curse of the drinking classes." -Oscar Wilde
I'm probably going to get modded down or flamed for being a heretic for daring to question modern scientific orthodoxy
Ah, the classic cry of the rebel without a clue.
Listen up, kid: you are not an iconoclast. You are not boldly speaking truth to power. You are not Martin Luther nailing his theses to the cathedral door. You are not a special snowflake.
Everyone who has ever worked in this project has thought of, and answered, every single one of your questions long ago. And those answers are easily available with a small amount of digging, which you would do if you had any interest in the actual answers instead of just self-aggrandizing puffery.
The correlation between ignorance of statistics and using "correlation is not causation" as an argument is close to 1.
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.
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