Delta-Like Fan on Mars Suggests Ancient Rivers Were Persistent

[Shyriath]

http://www.spacedaily.com/news/mars-water-science-03s.html

San Diego - Nov 17, 2003
Newly seen details in a fan-shaped apron of debris on Mars may help settle a decades-long debate about whether the planet had long-lasting rivers instead of just brief, intense floods.

Pictures from NASA's Mars Global Surveyor orbiter show eroded ancient deposits of transported sediment long since hardened into interweaving, curved ridges of layered rock. Scientists interpret some of the curves as traces of ancient meanders made in a sedimentary fan as flowing water changed its course over time.

"Meanders are key, unequivocal evidence that some valleys on early Mars held persistent flows of water over considerable periods of time," said Dr. Michael Malin of Malin Space Science Systems, San Diego, which supplied and operates the spacecraft's Mars Orbiter Camera.

"The shape of the fan and the pattern of inverted channels in it suggest it may have been a real delta, a deposit made where a river enters a body of water," he said. "If so, it would be the strongest indicator yet Mars once had lakes."

And making it a better bet that perhaps, even if only briefly, there was life?

[belle]

1. Cool! (n/t)

[pmbryant]

2. Very interesting, if somewhat speculative

Unfortunately, trying to interpret geologic history of an alien world from overhead photos alone is bound to be a highly speculative art.

We need to get a probe down there to actually inspect the rocks first-hand!

;-)

--Peter

[Shyriath]

4. What we need

more than probes. Robots can tell us much, but not enough.

Besides, it would be much more awesome if people went. :P

[On the Road]

3. Too Bad the Water is Not There Now

Mars is too small to sustain volcanic activity, which is needed to put greenhouse gasses in the air and trap heat. Carbon gradually reacts with the soil and becocmes part of the ground, and without volcanoes it will stay there.

The water in the air escapes very gradually into space. Mars needs to get hit by more comets to stay wet, but it's so much smaller than Jupiter that it's gavity can't attract many, and comets are not as frequent as they used to be. So Mars has dried out as it's gotten older.

[Shyriath]

5. Actually

Although undoubtedly some of the water has escaped, a lot of it may still be around in frozen form (in the ice caps, or in permafrost in the soil).

The volcanic activity thing does bring up something I hadn't thought about, though. There are various schemes batted around to one day 'terraform' Mars, to make it Earthlike, and at least some show promise. Carbon dioxide locked in the ground can be released to thicken the atmosphere, provided enough heat can be applied; same goes with frozen water. If there's not enough of either, it would presumably be possible to divert asteroids rich in volatiles (some sorts have a relatively high percentage of carbon and water-ice) to Mars to be broken up and evaporated into the atmosphere. If enough carbon dioxide could be put into the atmosphere, you could even get a greenhouse effect and make the warming self-sustaining for a while.

But none of this changes the part about volcanism. Mars is small enough that it lost most of its internal heat long ago; there doesn't seem to be any volcanism or plate tectonics, which are driven by internal heat. This means that there is no more mountain-building going on, no rejuvenation of the planet's surface. While a biosphere could probably be created on Mars for at least a while (maybe even millions of years), it seems to me that without a dynamic geology, the surface would get slowly eroded flat, and the biosphere would suffer as a result.

I wonder if, some time in the distant future, humans could figure out a way to re-heat the interior of a planet. In the realm of sci-fi, probably, but neat to think about.