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Fraser
2006-Apr-26, 04:11 PM
SUMMARY: This image, taken by ESA's Mars Express spacecraft, shows the Nanedi Valles region of Mars. These steep sided channels range in width from a few hundred meters to more than 5km (3 miles) across, and look like they were formed by quickly flowing water. But their origin is debated by researchers. Some think that liquid flowed under the surface and the ground collapsed above it, while others think that water did once flow on the surface.

View full article (http://www.universetoday.com/am/publish/nanedi_valles_system.html)
What do you think about this story? post your comments below.

antoniseb
2006-Apr-26, 07:28 PM
These things look similar to Hadley Rill on the moon (see Apollo 15). It seems unlikely that the moon had flowing water.

warpuppy
2006-Apr-26, 09:01 PM
The "valleys" look raised not sunken.

Corben
2006-Apr-26, 11:47 PM
Anyone can see those craters affected by the river? it seems that the river affected those crateres. If These channels have a width of more than 5km across, there is a LOT OF WATER down there!!

GOURDHEAD
2006-Apr-27, 01:01 PM
These things look similar to Hadley Rill on the moon (see Apollo 15). It seems unlikely that the moon had flowing water.Now that you raise the question of water on the moon, there seems to have been a lot of it around in the solar system when the moon was formed (even now), so it doesn't seem to be much of a stretch to assume the moon could have had a bunch of water initially. It would not have stayed there long once the sun got up to temperature though. I'm hoping there is still a lot of water beneath the surface of the moon and Mars to aid in the colonization of each site.

Anybody know how to calculate how long 5 bars of Venus's atmosphere would last on the moon? Could it be as long as 100 million years? 100,000 years?

tegwilym
2006-Apr-27, 04:04 PM
....the MRO is going to kick Mars Express in the butt! :lol:

I think it's always kind of interesting how ESA never really publicly "flaunts" their images from Mars Express. They have such totally amazing shots from that spacecraft, but we never hear about it unless you go to the website and look.
Well, who am I to talk, being a space geek I surf all the space sites daily, and I can't count myself as the "general public" who think the rovers are dead or wonder when the rovers are coming back! *ugh!*

Tom

antoniseb
2006-Apr-27, 05:21 PM
....the MRO is going to kick Mars Express in the butt!
What a strange display of nationalism. Mars Express has a really cool radar mapping tool which is telling us some interesting things about subsurface Mars. Mars Express is a generation or two behind MRO. Why not compare MRO to MGS, or the Viking Orbiter? They're all good.

JESMKS
2006-Apr-27, 05:46 PM
They look like stream formed encised meanders to me. The small
mesa looks out of place. Is it a remnant of a former higher land surface that has been removed by erosion?
Jack

ocalady
2006-Apr-27, 06:00 PM
The direction of light and shadow in this view of the Nanedi Valles on Mars does not appear consistent to me. The central depression is being lit from the opposite direction from the rest of the "valleys"

aurora
2006-Apr-27, 08:25 PM
Do the rilles on the Moon show side channels like the picture of Mars does? Or are the rilles on the Moon clearly lava flows, wherease these are a different liquid, most likely water?

raman
2006-Apr-30, 02:00 AM
The direction of light and shadow in this view of the Nanedi Valles on Mars does not appear consistent to me. The central depression is being lit from the opposite direction from the rest of the "valleys"

I agree, can anyone explain this?

antoniseb
2006-Apr-30, 10:01 AM
Take any black and white image of the moon. Turn it upside down. The craters might look like they are plateaus above the surface because the brain is used to seeing light in these images from the other direction.

BTW, welcome to the BAUT forum ocalady and raman.

drew4005
2006-Apr-30, 01:15 PM
There are lots of photos like these. The debate is always the same. Water. I have experience in fluid mechanics and engineering. This photo screams to me that they are CRACKS. Cracks subsequently filled over billions of years by sand and dust. Think about it. When Mars was formed there was a hot but cooling planet. A light thin crust moving over a fluid mantle/core. The crust would move and crack and cool. The fill pattern of the cracks is exactly the same as the craters that surround the "channels". Ever wonder why the "rivers" don't go anywhere? Our human interpretation of such photos is always coloured by our earthly experience.

antoniseb
2006-Apr-30, 01:25 PM
Our human interpretation of such photos is always coloured by our earthly experience.

This affects so many things in astronomy. Thanks for pointing it out.
BTW, welcome to the BAUT forum.

cope
2006-Apr-30, 11:25 PM
Though the scale is a bit to coarse to tell for sure, the sinuous valleys seem to be floored by a smooth, level surface that extends from one side of the valley to the other. If the valleys were formed by flowing liquid water, I would expect to see some incised gullies within the valley floors. Also, one would expect to see deeper valley depths on the outsides of the meanders and bars on the insides. However, again, because of the scale, this might not be apparent.

The collapse possibility seems have some merit, especially given the very recent discovery of sub-glacial "rivers" flowing beneath the Antarctic ice sheet.

Daniel Grist
2006-May-01, 12:39 AM
It must have been created by surface water, if it was created by under ground water the colapse wouldnt have left the perfect meanders in the river which we see in the missisipi river which is a surface river.

aurora
2006-May-01, 03:48 PM
When Mars was formed there was a hot but cooling planet. A light thin crust moving over a fluid mantle/core. The crust would move and crack and cool. The fill pattern of the cracks is exactly the same as the craters that surround the "channels". Ever wonder why the "rivers" don't go anywhere? Our human interpretation of such photos is always coloured by our earthly experience.

Well, actually, much of the original surface of Mars has been covered up by subsequent eruptions and dust deposits and impacts.

The cracks in question do not show a pattern that one would expect from a cooling surface, but rather have a branching pattern that one would expect from a flowing liquid, either water or lava.

And actually, the rivers do go places. They generally run out into a large plain where the deposits of material moved by the liquid fan out.

JESMKS
2006-May-01, 04:25 PM
Are there adjacent pictures available? The small area is not a depression but a flat topped mesa. I'm wondering if it is an outlier from some adjacent highland. It's origin is hard to explain from the picture.

01101001
2006-May-01, 05:50 PM
Are there adjacent pictures available? The small area is not a depression but a flat topped mesa. I'm wondering if it is an outlier from some adjacent highland. It's origin is hard to explain from the picture.
You're unlikely to see pictures of nearby areas from Mars Express. ESA is pretty parsimonious about releasing images. Maybe some day.

Google Mars can get you some context easily: Nanedi Valles (http://www.google.com/mars/#lat=6.036773&lon=-47.867431&zoom=8&map=visible). (Note: north is up instead of right as on the Mars Express image.) JMARS (http://jmars.asu.edu/data/) at Arizona State University can lead you to images from other spacecraft.

JESMKS
2006-May-01, 11:52 PM
The Nanedi Valles maps are great. The river system starts at an old crater. The elevation map shows the mesa, and several other small upland areas and a general upland area to the left. Thanks