Mars May Have Been 1/3 Ocean 118
coondoggie sends in a snippet from Network World, as is his wont: "It's possible that a huge ocean covered one-third of the surface of Mars some 3.5 billion years ago, a finding likely to reignite an old argument about that amount of water on the red planet, according to a new report. The study by the University of Colorado at Boulder is the first to integrate multiple data sets of river deltas, valley networks and topography from a cadre of NASA and European Space Agency orbiting missions of Mars dating back to 2001, the researchers claim." The National Geographic coverage of the news gives some air time to those doubtful that this study will prove definitive.
Always curious about where the water went (Score:4, Informative)
Re:Not funny (Score:5, Informative)
Mars has an atmosphere, not much of one to be sure, but it does have one. Why else do you think so many landers used parachutes to help slow their descent?
Re:We'll Never Know (Score:2, Informative)
Nah, we could date it really easily. There's radioactive carbon dating. Oh, won't work. Well, you can look at the sedimentation layers. Oh, won't work. Well, there's always guesswork. :)
There are other radiometric dating methods besids carbon-14, specially for things that old. One of them is rubidium-strontium (50 billion yeras half life?). It works on inorganic stuff too, although i don't know if it works for martian inorganic stuff, but I'm sure one could adapt it.
Really, the dating itself isn't as important as if water was or was not there.
I agree.
Re:maybe it's time to enlist the Japanese (Score:4, Informative)
Let's do the numbers.
The ascent stage (ie the Mars to Low Mars Orbit transport) needs about 4.1 km s^-1 of delta-V. About twice what you need from the Moon, but less than half what you need from Earth. The Mars orbit return vehicle, which doesn't need to land on Mars needs about 2.3 km s^-1 to get into a transfer orbit back to Earth. (figures from wikipedia).
This is definitely challenging, ascent stage most challenging of all. We need a rocket that can survive launch from Earth, 9 months coasting, aerocapture and aerobraking at Mars, impact with the Mars surface, a few months sitting on Mars and then take off with no support systems, deliver 4+kms^-1 of delta-V and automatically dock with the orbiting component of the system. The durability requirement pretty much rules out cryogenic fuels, and even relatively stable liquid fuels like kerosene/nitric acid might give trouble, both due to the cold conditions on Mars and the extra mass of tankage robust enough to survive the journey, so you're probably looking at solids.
A few quick checks reveal that good solid rockets have an ISP of maybe 265s, giving a mass ratio of perhaps 10 for Mars to Low Mars orbit, so we need an ascent stage roughly 90% of which is solid rocket propellant (or multiple ascent stages, adding complexity). Suppose we can get the payload capsule + docking system down to 10kg and our solid rocket motors are 95% propellant (5% nozzles and casing -- this might be optimistic) we get a mass of 200kg launching from Mars. This is actually less bad than I'd feared. Seems that a Viking sized lander could probably do it. A 1 ton or so lander includes a digging tool and maybe a mini-rover to collect 5kg of rock and load them into a 5kg capsule with some tiny thrusters on it. That sits on a 200kg solid fuel rocket that gets into Low Mars Orbit and drops the capsule, which docks with a similar sized vehicle with 100kg of solid fuel some batteries and electronics and a heat shield for Earth reentry.
So we need two launches to Mars transfer, each about 1 ton payload, plus heat shields for aero-braking/aero-capture on Mars. Should be doable as two medium large launches from Earth