Starship Asterisk*

Frankcheck wrote:Could it be the result of huge asteroid detonation passing really close to mars? It looks like!

No. This was discussed and dismissed in the earlier posts within this topic.

I'd like to know how would Earth look like if stripped of all water and "greens".. That'd be a cool sight to see.

The other question I'm sure someone can answer is if this Mars picture represents the rift as relatively equatorial, as several of Earth's rifts are more aligned pole to pole.
jambo

Maps show that the Valles Marineris has a east-west orientation. And this makes me wonder whether it may have been winds that produced this Valley.
[Possible when the Original surface consisted of pumice e.g.]
In stead of a Valley that remains unchanged for billions of years, i think it's more likely that it has been formed over a period of billions of years, and that it's still being formed and maintained.
And -by the way- if it would have been there for billions of years, i think we can also safely assume there has never been any life on mars...

Ludo wrote:I'd like to know how would Earth look like if stripped of all water and "greens".. That'd be a cool sight to see.

Really? I like deserts, but I still think the Earth looks way cooler (and is way cooler) the way it is now.

superwillbee wrote:Maps show that the Valles Marineris has a east-west orientation. And this makes me wonder whether it may have been winds that produced this Valley.

No. It is pretty clear that it is a tectonic structure formed a very long time ago, and subsequently eroded by flowing water, CO₂, and/or soil.

Chris Peterson wrote:

superwillbee wrote:Maps show that the Valles Marineris has a east-west orientation. And this makes me wonder whether it may have been winds that produced this Valley.

No. It is pretty clear that it is a tectonic structure formed a very long time ago, and subsequently eroded by flowing water, CO₂, and/or soil.

So let's say it is a tectonic structure of mainly pumice-like-materials, formed a very long time ago, and subsequently eroded bij flowing water and/or wind, CO2 and/or soil. Waters moving west and east due to ebb and flood, and winds tending to go east and west too, around the equator of planets.
As sand dunes look very much like beach structures, i doubt if we can be sure and choose between water and winds that would have formed this Valley in billions of years. And i very much doubt we can be 100% sure about it today, millions of years later. And assuming there was water, i'm pretty sure there must have been an atmosphere too, and winds.

Just to say "No. It's pretty clear".. etc. is no fun at all. Dear Chris Peterson, give doubt a chance, don't be a kill-joy!

Give doubt a chance!

superwillbee wrote:

Chris Peterson wrote:

superwillbee wrote:Maps show that the Valles Marineris has a east-west orientation. And this makes me wonder whether it may have been winds that produced this Valley.

No. It is pretty clear that it is a tectonic structure formed a very long time ago, and subsequently eroded by flowing water, CO₂, and/or soil.

So let's say it is a tectonic structure of mainly pumice-like-materials, formed a very long time ago, and subsequently eroded bij flowing water and/or wind, CO2 and/or soil. Waters moving west and east due to ebb and flood, and winds tending to go east and west too, around the equator of planets.
As sand dunes look very much like beach structures, i doubt if we can be sure and choose between water and winds that would have formed this Valley in billions of years. And i very much doubt we can be 100% sure about it today, millions of years later. And assuming there was water, i'm pretty sure there must have been an atmosphere too, and winds.

Just to say "No. It's pretty clear".. etc. is no fun at all. Dear Chris Peterson, give doubt a chance, don't be a kill-joy!

Give doubt a chance!

I prefer to base my understanding on evidence. And the evidence in this case doesn't leave much room for doubt about the general processes involved here.

You propose, without justification or explanation, a "tectonic structure of mainly pumice-ike-materials". Yet we have no evidence for the existence of such structures, either on the Earth or Mars. The primary output of volcanic regions (like Tharsis) is magma, leading to basaltic rocks. What explanation would you propose for producing thousands of meters of pumice, a material only observed in shallow beds and as isolated stones and pebbles?

Aeolian bedforms and other structures are certainly present on Mars, and are similar to those on Earth. They are readily distinguished from fluvial structures. And neither explains a structure like Valles Marineris, while a tectonic rift zone explains every observed feature, and is consistent with the volcanics and plate structures seen in the region.

The bottom line is that yours is an explanation in search of a question.

Thank you, Chris!
For too long, The Starship has been home to Fiction, to Fairie and to Fantasie.
Without being Mr.Gradgrind, let us return to Facts, nothing but Facts.
Whatever the enjoyment and Fun of a Flight of Fancy that is started by the question , "What if...?", the APOD deals with the real Universe and a real discussion of tenable theories that are supported by the facts is more satisfying than speculation!

Bah, humbug!
John

JohnD wrote:Whatever the enjoyment and Fun of a Flight of Fancy that is started by the question , "What if...?", the APOD deals with the real Universe and a real discussion of tenable theories that are supported by the facts is more satisfying than speculation!

I honestly don't understand the mindset that chooses to reject clear advances in knowledge in favor of speculation. There are always those who look at every incremental gain in knowledge as an opportunity to speculate on much less likely possibilities. Surely, the most wonderful and satisfying thing is the realization that with new evidence we usually know just a little bit more about the Universe. What can be better than that?

Valles Marineris has been compared with the Grand Canyon, I would posit that the Great East African Rift Valley is a better comparison. Both the size and origin of V M will be more similar to the size and origin of the Great East African Rift Valley than to the Grand Canyon. Perhaps it is simply because the Grand Canyon is more commonly known by the general public it is preferred.

I absolutely agree, Stephen.
That the Grand Canyon is familar is not only because it is a tourist attraction, it is so because it is so small it is possible to see it in one glance!

The Great African Rift Valley on the other hand is too vast to be seen as such, save from space. So I searched for satellite images, and found that there are many but few that give the same dramatic image as those we see of the VM on Mars! But the following site has done a great job of integrating images from many sites to display Earth's geophysiognomy, including simulated views of the GRF: http://earth.imagico.de/view.php?site=rift2a

But using the same formula as I did for the Valles, I get only 15,000 Cubic kilometers for the volume of the GRV, because I find a mean depth is given as only 125metres, and I don't know if this includes the depth of the lakes of the Rift, or is ground and water surface depth. This shallow depth is because unlike on Moars, the rest of the Earyh's surface has been scoured to at least partially fill in the Rift!
But Lake Tanganyika alone is said to be 570m deep and to hold 18,000 cubic kilometers of water!
More time needed to list the other lakes' volumes and sum them, but none available right now.
John

BDanielMayfield wrote:

Ludo wrote:I'd like to know how would Earth look like if stripped of all water and "greens".. That'd be a cool sight to see.

Really? I like deserts, but I still think the Earth looks way cooler (and is way cooler) the way it is now.

You will probably never read this since it's been past long but that was not my point. Of course the Earth looks great as it is now.

What I meant was from a geological point of view. To watch Earth's body stripped of its "clothes" and see what's really going on with our surface, as we do with Mars just by looking. But I guess it's possible if I look for maritime mappings and the sort.. I presume every inch of our planet has been scanned one way or another.

Interesting Youtube find John
It appears that most islands couldn't stand without the support of their oceans

Laputa springs to mind.

Thought Lua might be amused

Thanks for posting this! The song is a bit distracting but the content was exactly what I was looking for. I wasn't expecting so many peaks on the bedrock outside of the ridges and more like ridges followed by soft plateaus everywhere else... Nothing like what we see on Mars.

If our orbit was outside of the habitable zone we were investigating our planet, I think it'd be very easy to identify the "surface" continents and the regions previously submerged by water.

If you aren't joking, BMA was.
In that video the vertical scale is grossly exaggerated. Watch it again just before the 10 second mark.
John

Ludo wrote:

BDanielMayfield wrote:

Ludo wrote:I'd like to know how would Earth look like if stripped of all water and "greens".. That'd be a cool sight to see.

Really? I like deserts, but I still think the Earth looks way cooler (and is way cooler) the way it is now.

You will probably never read this since it's been past long but that was not my point. Of course the Earth looks great as it is now.

I read a lot. Yes, I didn't think you were being literal, but taking your comment at face value was amusing, at least to me. I agree, most of Earth looks great now, as long as you don't look too closely.

Sorry if I caused offense.

Bruce

The text explanation mentions that several geological processes have been identified in the canyon - anyone know what they are?

Ludo wrote:I'd like to know how would Earth look like if stripped of all water and "greens".. That'd be a cool sight to see.

National Geographic has a special called "Drain The Ocean" 6 part series on youtube

Here is another NatGeo called "Light the Ocean" regarding making the oceans transparent

On a lesser scale, just finished watching a documentary on UK Channel 5, about the D-Day landings. A month of intensive sonar searching followed up by Remote cameras, divers and minisubs had identified hundreds of hulks, of tanks, landing craft and ships on the bottom of the Gulf of the Seine, off the landing beaches. It had a sensational title, "D-Day's Sunken Secrets" but was respectful and I'm sure adds to the history of that Day.

The last sequence imagined that the Gulf could be drained, and showed, of course in simulation, what it would be like. Water draining past and oput of the hulks, in astonishing realistic CGI.

Complete thread diversion, except this does deal with 'draining the ocean'!
JOhn