Gale Crater held a massive lake

[G'th]

Surprised this hasn't been posted about yet. The Curiosity team announced today that Gale Crater was home to a massive lake, that apparently had to have been there for millions of years, which also suggests that the rest of the planet had to have been loaded with water in order for that to happen.

http://www.theverge.com/2014/12/8/7354299/new-nasa-findings-show-gale-crater-once-held-a-massive-lake

[numerobis]

The press release:

http://www.jpl.nasa.gov/news/news.php?feature=4398

Yet more confirmation of the warm wet mars hypothesis, if it holds up.

[Aethon]

Mars quakes and shallow lakes combined to make the sedimentary rocks we see today.

http://www.nasa.gov/jpl/mro/signs-of-ancient-mars-lakes-and-quakes-seen-in-new-map/index.html#.VItzkSvF-Yc

Edited December 13, 2014 by Aethon

[cantab]

It falls into the category of confirming what we believed, but it's a good result nonetheless.

[Scotius]

I wonder if life managed to appear there before water dried up\froze. Finding even one stromatholite would be a huge discovery.

[Godot]

The more we find out about the past of Mars, the more reasons we find for a new mission to Mars in order to find traces of past or present (microbial) life on Mars

(this time, in contrast to the Viking landers, perhaps with a mobile probe)

[KerikBalm]

I simply cannot look at this image of mars:

And not think "duh" when people talk about a "wet" mars

[Scotius]

Valles Marineris would be an awe inspiring sight then

[BagelRabbit]

Gale Crater, I should mention, is one of the smaller ones below the cluster of volcanoes on the right side of the screen; it's the "bluest," lowest-elevation crater on the boundary between the green, lower-elevation areas and the red, higher-elevation areas. Looking at the tallest volcano in the region, draw a line through the two craters right below it and you'll arrive at Gale Crater. (Hope this makes sense.)

Is it bad that I know this to be the case, despite never seeing this map before? I might want to confirm this, hold on sec...

Yep. Here's an image from the BBC.

I feel really geeky right now

[Newt]

There are other proposals for the dichotomy between North and South on Mars. Giant impact, for instance. I am not really sure that simply wetness would explain the full difference between the two halves of the planet. Something caused a difference, but I really do not think that oceans are widely taken as an answer. Maybe that will change.

P.S. You are not alone in recognizing that sort of thing here:wink:, Upsilon.

[cantab]

Closer up, I'm more often struck by how familiar Mars looks. These are channels, sedimentary rocks, sand dunes, that all wouldn't look out of place on Earth.

If Mars was once a truly wet world, then its current desertification is one of the great tragedies of the cosmos.

[lajoswinkler]

With all those sediments in layers, it had to be a wet world. It must've looked amazing back then. Something like Laythe, but with a lot more land.

Keep your fingers crossed for stromatolithes.

[Frozen_Heart]

I hope that signs of life are found. It would definitely encourage future Mars exploration.

[KerikBalm]

I know that there are other proposals for the dichotomy. The main one is a giant impact hypothesis, and then the channels are just transient water leading into the crater.

But the channels don't look like how channels look when they just flow until they've evaporated away/soaked into the ground. They look like deltas flowing into an ocean.

It seems strange to think it was just an impact crater if none of the channel flows go further "down" into the "crater", but they all stop at about the rim. That they all end right where the dichotomy begins suggests they stopped because they flowed into a ocean.

The two are not mutually incompatible:

Giant impact makes lowland depression, water flows into the low depression, forming an ocean.

As to the lack of fossile stromatolites and such... I'm quite disappointed by the lack of them, or fosillized biofilms.

Even if there was water for millions of years, that may not have been enough.

Its hard to date the start of life on Earth, but about 0.1 - 0.2 billion years after Earth could support water seems to be reasonable.

ie 100-200 million years.

If Mars had an ocean (or just a lake in that crater) for 20 million years, it may not have been enough.

There may have been some very interesting biochemistry going on, near the border of life and non life, along lines that are hypothesized in abiogenesis theories...

But I'm starting to think that Mars never had "true" life, given the apparent lack of any fossile biofilms in the places where water flowed.

[Albert VDS]

Keep your fingers crossed for stromatolithes.

But can MSL detect stromatolites?

[KerikBalm]

Stromatolites and fossile biofilms are macroscopic, and could be seen with a camera if exposed.

[Scotius]

Remember: there was a lot of erosion and sedimentation over the million of years since Mars dried up. Our probes and rovers explored only very small area of the whole planet. It's entirely posssible we simply missed traces of life, because they were covered by sand or simply outside of the searched area.

[KerikBalm]

Not so much erosion as on Earth. The abundand crates show that to be true.

Also of note is the lack of plate techtonics, which would be subducting old crust.

For as long as there was liquid water assisting in erosion, there should have been life growing, if it was there.

As the waters receded, the life there would be the last life, undisturbed by future organisms.

If all life on Earth suddently died, we'd have a lot more fossils, because current life generally destroys dead things before fossilization.

It was a long time since Earth was covered in microbial mats and stromatolites. The areas of our crust that are from the right time, bear tell-tale signs.

Now I don't know what % of the areas that old hold evidence like that.

But i imagine if there was something like this:

Which should have been around the edges of a lake (and continued to move inward as the water receded), and stuff like that should be preserved.

Maybe its been buried in dust since then... but anyplace we find exposed rock outcroppings, or even streambeds with rounded pebbles, it would seem, given that there would have been no new deposition by volcanism or water mediated sedimentation... that we should find fossil structures from microbe colonies, if they were there....

Yes, the surveyed areas are small, but they are right at where you'd expect to find them.

There's no vegitation to hide the signs.... one can see for miles around on the cameras.... the rovers have been driving a long ways... not a hint.

The entire surface is very old, I think when you find such old surfaces on Earth, it doesn't take that long to spot signs of life.

I'm becoming pessimistic about it ever having had life.

That said, I still want to check out those martian geysers/"spider features"/dark dune spots... they look so... dynamic, and some biological explanations have been put forth.

And they are where there is seasonal defrosting and water ice, it doesn't seem impossible for some hardy life to survive there.

[Aethon]

Big week for Mars. I've been in a 0.90 coma for a bit but here's some info.

MSL (Curiosity) Confirms ancient organic chemistry on Mars, and an unusual methane spike.

http://www.nasa.gov/press/2014/december/nasa-rover-finds-active-ancient-organic-chemistry-on-mars/index.html#.VJNVRSvF-Yd

Meteoritic evidence suggests Mars has a distinct, global reservoir of ice or water near the surface.

http://www.nasa.gov/press/2014/december/nasa-planetary-scientists-find-meteoritic-evidence-of-mars-water-reservoir/index.html#.VJNXSyvF-Yd

[Aethon]

Results from the Sample Analysis at Mars (SAM) instrument on the Mars Science Lab (MSL Curiosity):

http://www.nasa.gov/content/goddard/mars-organic-matter/#.VJSwhF4ABA

[NERVAfan]

Precambrian fossils are really hard to find on Earth (OK, some of that is due to rocks that old being relatively rare, but not nearly all of it). I think it's way too early to say we "should" have found fossils if they were there - we've only geologically inspected a miniscule part of Mars (the orbiters don't have enough resolution for that).

And life could totally have survived. Endolithic forms of life would do fine on Mars if there's even an ultra-tiny trickle of liquid water in the subsurface. (I don't know how long it would take to evolve an endolithic mode of life though.)

I agree it's still very unknown whether Mars was watery long enough to develop life (of course, we don't know how long that takes either - it could have developed practically immediately once Earth had liquid water. There are few to no rocks that old.)

[KerikBalm]

Precambrian fossils are really hard to find on Earth (OK, some of that is due to rocks that old being relatively rare, but not nearly all of it).

The rocks are very rare... of those rocks, many are not comparable. Ideally, we'd like to only look at those rocks that were exposed to the surface. Finding the core of a 10m boulder isn't going to tell you much. The erosion processes on earth are much more severe. Those rocks which do preserve ancient lakebeds and seafloors, do very often bear telltale signs of life, ie fossilized microbial mats.

Of course, microbial mats themselves are somewhat of an achievement, as that is basically already evidence of cooperative behavior and an increasingly complex ecosystem. It could have had life without having microbial mats.

I think it's way too early to say we "should" have found fossils if they were there - we've only geologically inspected a miniscule part of Mars (the orbiters don't have enough resolution for that).

Yes, it is too early, but we've inspected the geologically most likely places... the ancient seafloors/lakebeds. So I'm now pessimistic that Mars was ever thriving with life to a comparable degree the way Earth was 3.8-3.5 billion years ago.

The more curiosity drives around sediments from a putatively habitable epoch, and finds no signs that it was inhabited, the more pessimistic I become.

And life could totally have survived. Endolithic forms of life would do fine on Mars if there's even an ultra-tiny trickle of liquid water in the subsurface. (I don't know how long it would take to evolve an endolithic mode of life though.)

Indeed, I recall that there was some probable liquid on the strut phoenix lander. Those geysers are CO2 ice overlaying H2O, and even the H2O sublimates in many places. If there is an icy overlay, and a buildup of pressure btween the CO2 ice and H2O ice, as they predict for these geysers, then I'd think there could be a niche where the pressure is higher than the triple point of water - at the same time there is sunlight, some protection from radiation (CO2 ice), and a carbon source.

I can imagine life surviving even there.

Even if plate tectonics has stopped, surely there is still some internal warmth.... if life ever started on mars, I suspect it would still be clinging on... somewhere on or in the planet.

I'm just not optimistic that it ever started.

[NERVAfan]

The rocks are very rare... of those rocks, many are not comparable. Ideally, we'd like to only look at those rocks that were exposed to the surface. Finding the core of a 10m boulder isn't going to tell you much. The erosion processes on earth are much more severe. Those rocks which do preserve ancient lakebeds and seafloors, do very often bear telltale signs of life, ie fossilized microbial mats.

Of course, microbial mats themselves are somewhat of an achievement, as that is basically already evidence of cooperative behavior and an increasingly complex ecosystem. It could have had life without having microbial mats.

Yeah, exactly. I wouldn't expect fossils you could see without a microscope.

Yes, it is too early, but we've inspected the geologically most likely places... the ancient seafloors/lakebeds.

Only a tiny portion even of those.

[Kryten]

Precambrian fossils of complex life are rare. Stromatolites and microbial mats are common.

[Aethon]

Hmmm. No new images from MSL (Curiosity) since December 22, five days ago. The last were sixteen hazcam/navcam images on sol 845, and it is now sol 850. This is highly unusual, even over a holiday. I can only remember this happening twice before, during computer reboots. Lets hope all is well with MSL.

http://mars.jpl.nasa.gov/msl/multimedia/raw/