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Wagamaga OP t1_iu0h4he wrote

A recently released set of topography maps provides new evidence for an ancient northern ocean on Mars. The maps offer the strongest case yet that the planet once experienced sea-level rise consistent with an extended warm and wet climate, not the harsh, frozen landscape that exists today.

“What immediately comes to mind as one the most significant points here is that the existence of an ocean of this size means a higher potential for life,” said Benjamin Cardenas, assistant professor of geosciences at Penn State and lead author on the study recently published in the Journal of Geophysical Research: Planets. “It also tells us about the ancient climate and its evolution. Based on these findings, we know there had to have been a period when it was warm enough and the atmosphere was thick enough to support this much liquid water at one time.”

There has long been debate in the scientific community about whether Mars had an ocean in its low-elevation northern hemisphere, Cardenas explained. Using topography data, the research team was able to show definitive evidence of a roughly 3.5-billion-year-old shoreline with substantial sedimentary accumulation, at least 900 meters thick, that covered hundreds of thousands of square kilometers.

“The big, novel thing that we did in this paper was think about Mars in terms of its stratigraphy and its sedimentary record,” Cardenas said. “On Earth, we chart the history of waterways by looking at sediment that is deposited over time. We call that stratigraphy, the idea that water transports sediment and you can measure the changes on Earth by understanding the way that sediment piles up. That’s what we’ve done here — but it’s Mars.”

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2022JE007390

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[deleted] t1_iu3qnb1 wrote

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GeoGeoGeoGeo t1_iu55dd3 wrote

>...two scientists (one is a director of NASA’s climate studies and another is an astronomer and physicist, IIRC) argued that there could have existed an ancient industrial civilization on Earth long enough ago that we wouldn’t be able to gather sufficient evidence of its existence due to limitations of dating techniques.

That's not what they argued. The take away was that any ancient civilization would be detectable through large, abrupt, isotope excursions (anomalies). For example our civilization will eventually be compacted into a thin sedimentary layer; however, stable isotope anomalies of carbon, oxygen, hydrogen and nitrogen will be detectable - discerning them from natural excursions may prove difficult though other biomarkers would help shed light on the full story. Plastics, fossils, and radioactive isotopes in conjunction with the former (among a few others) would surely be a clear indicator of an ancient civilization.

You can read the full study here: The Silurian hypothesis: would it be possible to detect an industrial civilization in the geological record?

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[deleted] t1_iu7s31g wrote

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GeoGeoGeoGeo t1_iu7yp7z wrote

You're missing the forest for the trees, and they hint as much as well. No singular piece of evidence can be used as proof of an ancient civilization because it's likely too difficult to distinguish from natural lines of evidence of an identical nature; however, as I said earlier, and as they say in the paper, combining several lines of evidence can distinguish from natural events such as carbon isotope excursions with a large long-lived radiogenic isotope excursion (^(244)Pu and ^(247)Cm), and perhaps plastics as well.

I might add that the paper doesn't really dive into quantity too much with stable isotopes, though I believe it could benefit from that analysis. What I mean by this is that while they discuss abrupt events (hyperthermals), they don't really go into abrupt abrupt events. For example, while they discuss ^(13)C excursions such as the during the PETM they don't note the difference in carbon flux between that event and modern day climate change. For example, the PETM released roughly 3000 Petagrams of carbon over a period of ~6000 years. It is hypothesized that under a worst-case-scenario our civilization could release 5000 Petagrams of carbon over a period of 500 years. There is nothing in the geological record that even comes close to those values on global scales. On a yearly basis the PETM rates range from about 0.3 to 1.5 Pg C/year. For comparison, the current rate of carbon release to the atmosphere is nearly 10 Pg C/year. And of course the more lines of evidence one uses the more clear the picture becomes.

As for Mars, I'm not quite sure what dating techniques become irrelevant. Absolute dating methods would work just as well on Mars as they do on Earth, and Martian meteorites as well as lunar samples have been dated using radiometric techniques.

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kozy138 t1_iu0pedg wrote

This is actually amazing. Is the assumption that an ocean would almost certainly have thermal vents that created conditions for rudimentary forms of life?

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Sierra-117- t1_iu0yv16 wrote

No, because we aren’t sure if Mars ever had a hot core. Right now, it’s not hot enough to create geothermal activity. So if an ocean existed on mars today, life would not form via geothermal activity. But maybe in the far flung past, who knows?

Also, geothermal activity isn’t the only theory of abiogenesis. I’m quite fond of the clay hypothesis. Where molecules being wetted and dried continuously in the presence of silica crystals (like on the bank of a river) will form complex self assembling structures.

Edit: just to clear up some things. Yes, mars core is hot. But it’s much cooler relative to earth. But I’ve just learned that new research thinks mars may still be volcanically active! Just far more dormant than a planet with a very hot core and mantle like earth. Earth likely experienced a massive event (giant impact hypothesis) that gave it a lot of excess energy, which means a lot more active volcanoes. Perfect for life!

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Darkelement t1_iu11o98 wrote

If Mars didn’t have a hot core, how could it have produced volcanoes? Or is that also something unknown?

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Sierra-117- t1_iu1anpm wrote

Well you misunderstand what produces volcanos.

The core helps KEEP a planet warm, and keep lava flowing. But the lava itself is created and flows from the mantle, not the core. So some believe that Mars has a relatively cool core, but it’s mantle was still hot after formation.

Basically, a cool core with a short time of volcanic activity after formation due to heat trapped in the mantle.

Which is why we don’t see volcanic activity on mars today, but we see evidence of it in the past. The mantle is now cooled.

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Darkelement t1_iu1bkfy wrote

I guess it could be a misunderstanding, but what heat the mantle up in the first place? Would those forces not also create a hot core? Does this imply the core was never warm?

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Sierra-117- t1_iu1cvzm wrote

Well it takes a lot more energy to melt metals into liquid than rock.

Metal also has a higher rate of energy transfer. So the metal cools faster, and takes far more energy to stay hot.

The core is also more stable than the mantle, meaning is experiences less friction and therefore produces less excess heat.

The heat from the core will constantly radiate into the mantle, so the mantle is constantly gaining energy while the core cools. Because the core is HOT, just not hotter than we would expect under the given pressure.

Lots of factors, and there’s a lot more I could list! But basically it comes down to: the core has now cooled to a stable temperature, therefore the mantle has cooled to a stable temperature, therefore volcanic activity is likely to cease.

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TheLastForestOnEarth t1_iu1vvbd wrote

In Earth's case I believe one hypothesis is that the impact of two planets created Earth and its moon. The incredible heat of our core may simply be left over from this collision.

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goneinsane6 t1_iu26wio wrote

The primary contributors to heat in the core are the decay of radioactive elements, leftover heat from planetary formation, and heat released as the liquid outer core solidifies near its boundary with the inner core. This heat radiates/transfers to the mantle. Due to Mars' smaller size and the square-cube law, it has a higher surface area relative to its core and mantle (compared to a larger planet). This causes more heat to radiate out compared to the Earth and is the main reason why Mars' core is now mostly cooled. Mars simply cooled faster because it is smaller.

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kozy138 t1_iu12mwq wrote

Without a core, how would Mars have been warm enough to contain liquid water? Extremely high salt concentrations that lower the melting temperatures?

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Sierra-117- t1_iu19cto wrote

Very good question!

It was able to maintain liquid water through a thicker atmosphere than it currently has. Basically, a greenhouse effect. It would still be freezing at night though.

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Sierra-117- t1_iu1dxy8 wrote

Also I realize my comment was confusing. I’m not saying it has a completely cool core, we’re a long way off from that. But it’s core is relatively cool, and therefore volcanic activity has pretty much ceased.

But the crust of a rocky planet gets most of its energy from the star it orbits

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Dejan05 t1_iu19fo9 wrote

How would it not have a hot core? Under such pressure it sounds impossible for it to not be hot to some degree

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Sierra-117- t1_iu1bhya wrote

Yes! It is still very hot, like the core of any planet. Gas giants have cores hotter than the surface of the sun.

But when you say “hot core” in planetary science, it means a REALLY hot core. As in, hotter than it should be given the pressures involved.

This excess heat usually comes from conditions experienced during formation. Earth’s core is a hot core, because we currently believe a small planet collided with the early Earth! (Though this is also still only theory).

But yes, the interior of mars is very hot. Just not hot enough to support continued volcanic activity in the mantle/crust.

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mojojojo31 t1_iu0v2bh wrote

What happened to all that water?

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margenreich t1_iu3z8a6 wrote

It could be all accumulated at the poles as ice. That’s at least one plausible theory. Most freshwater on earth is on the poles too. On Mars it would be hidden under millennial of dust, so really hard to say as long no rover checks there or we do it in person. From afar it’s really hard to tell

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rainman213 t1_iu1w2cf wrote

So these will be the same tests aliens run on earth in a few thousand years to determine humans were here????

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BeowulfShaeffer t1_iu0y2np wrote

How long ago are we talking? Millions of years? Billions?

You can pick practically any bit of fossilized seabed on Earth and evidence of life. If Mars really did have a sea that harbored multicellular life I would expect the evidence wouldn’t be that hard to find.

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ThickPrick t1_iu2acll wrote

We actually came from Mars to Earth. We destroyed that planet and moved here. The shuttle dropped humans here and on the way back to get more of us was destroyed upon reentry to Mars. Now we have destroyed this planet and look to return home.

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jackfrost7890 t1_iu2t8lf wrote

That goes along with a theory I have that we keep going back and forth between Earth and Mars because we keep wrecking each one. Then by the time we wreck the one we are on the other seems like a better solution it would kinda explain the pyramids on Earth and Mars.

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C4-BlueCat t1_iu3ptya wrote

Doesn’t explain Venus though - that one used to have an earth-like climate before its runaway greenhouse process

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jackfrost7890 t1_iu78o06 wrote

Same theory but seems even more possible considering how much everyone is talking about greenhouse gases and climate change. They say there is alot of methane trapped in the ice caps. And methane is more insulating then carbon.

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