[HN Gopher] Photos from NASA's Perseverance rover indicate ancie...
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Photos from NASA's Perseverance rover indicate ancient flash floods
on Mars
Author : el_duderino
Score : 92 points
Date : 2021-10-10 17:40 UTC (5 hours ago)
(HTM) web link (www.science.org)
(TXT) w3m dump (www.science.org)
| johnklos wrote:
| We've known about these for decades - this is just confirmation
| because there were naysayers that insisted otherwise.
| ChuckMcM wrote:
| Yes and no right? What I mean is that this is how science
| works, where someone says "This is the answer to this question"
| and someone else says "No there is this other answer to the
| question." And what follows are a series of investigations into
| why the other person's answer is wrong and your answer is
| right. Eventually a lot of evidence has been gathered and a lot
| of theories and predictions have been tested, and then we can
| say "With everything we know so far, the only possible correct
| answer is 'A'" which becomes the answer of record. And the
| longer it holds up against people trying to prove it could also
| be 'B' or for some reason it could not be 'A' then the more
| consensus we have that it is the correct answer.
| cronix wrote:
| Or, it's good to confirm what you think you know.
| harwoodleon wrote:
| I was watching the ISS live feed going over North West Africa and
| up to Italy. The landscape was red and arid and it struck me just
| how 'Mars like' it looked.
|
| It got me thinking that Earth could be facing the same destiny
| many aeons from now. It's hard to imagine with the amount of H2O
| on the planet right now, but if it can happen to Mars (the
| atmosphere is stripped away), it could happen here I suppose.
|
| But I wonder if a Venus situation is more likely first, because
| of our proximity to the Sun?
|
| This discovery certainly makes me feel that lifecycle of planets
| is an awesome thing.
| krisoft wrote:
| About North Africa: archeological findings seems to imply that
| what is now the Sahara desert was much more lush and wet
| relatively recently. We have human made cave paintings of river
| animals in areas which are very dry nowadays. It is thought
| that the area dried out relatively suddenly about 5k years ago.
| That is basically yesterday as far as geological timescales go.
|
| When I learned about this I got kinda scarred. If the climate
| of an area can change this drastically all of a sudden that
| means to me that the climate system is a lot less stable than I
| previously have thougt.
| jandrewrogers wrote:
| Something similar happened on a smaller scale in North
| America with Lake Lahontan[0], which covered much of Nevada
| after the last ice age. If you walk the old shoreline up on
| the mountainsides, it is not uncommon to find evidence of the
| neolithic people that lived on its shores before it
| disappeared.
|
| [0] https://en.wikipedia.org/wiki/Lake_Lahontan
| MayeulC wrote:
| https://en.wikipedia.org/wiki/African_humid_period
|
| IIRC one of the causes might be orbital precession, which
| could lead to a re-greening in a few millenia.
| mixmastamyk wrote:
| The much larger mass, gravity, and magnetic field of Earth
| prevents large scale atmospheric losses. Whether we have the
| resources to ignite another Venus remains to be seen.
| exporectomy wrote:
| Remains to be seen or is already known to be impossible? All
| the carbon in fossil fuels originally came from the
| atmospheric CO2, didn't it? And it was never as hot as Venus.
| What are the steps we would need to take to make it as hot as
| Venus in any kind of physically possible scenario?
| mixmastamyk wrote:
| Too many variables to account for.
|
| Didn't mean to imply we could get "as hot as" Venus, which
| is unlikely due to our distance from the Sun. But hot
| enough to boil water? Possibly, given a runaway chain
| reaction. Not sure.
| virtue3 wrote:
| You are drastically under-estimating the effects of other
| compounds in the atmosphere.
|
| Methane is a really good example.
|
| HFCs were a great bit of disaster for a bit there as well.
|
| from: https://en.wikipedia.org/wiki/Greenhouse_gas#Impacts_
| on_the_...
|
| "The contribution of each gas to the greenhouse effect is
| determined by the characteristics of that gas, its
| abundance, and any indirect effects it may cause. For
| example, the direct radiative effect of a mass of methane
| is about 84 times stronger than the same mass of carbon
| dioxide over a 20-year time frame[27] but it is present in
| much smaller concentrations so that its total direct
| radiative effect has so far been smaller, in part due to
| its shorter atmospheric lifetime in the absence of
| additional carbon sequestration. On the other hand, in
| addition to its direct radiative impact, methane has a
| large, indirect radiative effect because it contributes to
| ozone formation. Shindell et al. (2005)[28] argues that the
| contribution to climate change from methane is at least
| double previous estimates as a result of this effect.[29]"
| [deleted]
| 5faulker wrote:
| And here's we are at a paradox, where one side is attempting to
| escape imminent danger by traveling outside Earth, and in doing
| so potentially accelerating its instability.
| heavyset_go wrote:
| > _It's hard to imagine with the amount of H2O on the planet
| right now, but if it can happen to Mars (the atmosphere is
| stripped away), it could happen here I suppose._
|
| Mars' atmosphere isn't protected by a strong magnetic field
| because the planet isn't geologically active, unlike the Earth.
| Gasses escape from the Earth into space constantly, but not at
| a rate that will leave the Earth like Mars before the sun
| becomes a red giant.
|
| In billions of years, the sun will expand and probably blast
| away the Earth's atmosphere before possibly engulfing it later.
| kibwen wrote:
| I'm no astrophysicist, but I'm under the impression that the
| effect of the magnetosphere is popularly overstated. Rather,
| the reason that Earth still has its atmosphere and Mars
| doesn't is that Earth has the gravity to hold onto it more
| tightly, and Mars is just too small. Hence why Venus, which
| also (curiously) has no dynamic magnetosphere, still has an
| atmosphere: it's 80% the mass of Earth (compare Mars, which
| is 10% the mass of Earth).
| therealdrag0 wrote:
| I once saw a clip of Elon saying the fast way to terraform Mars
| is to nuke the poles. And now that I'm watching The Expanse it
| got me thinking about that. Except for the possible impact on
| passive scientific study, it seems like a process worth starting
| sooner than later right?
|
| Any thoughts on this. Or are there other better ways to get a
| better atmosphere and water on Mars?
| spfzero wrote:
| Right now Mars is a pristine snapshot of processes I think we'd
| like to learn more about. We should propose Terraforming only
| after we think we've learned pretty much everything we care
| about.
|
| I'm not against terraforming eventually, but I think we need to
| give exploration a bit of time before considering which early
| 21st century tech would work best.
| JumpCrisscross wrote:
| > _nuke the poles_
|
| Nuking asteroids to steer them into the poles would seem like a
| better solution. (Haven't run the math on the delta-v for
| candidate impactors, though. You'd need to manage energy to
| avoid losing too much to space.)
| IAmGraydon wrote:
| I think that comment was tongue in cheek. It would take an
| utterly massive amount of nuclear weapons to appreciably melt
| the poles and it would likely poison the environment.
| tsimionescu wrote:
| First of all, never listen to Elon Musk on scientific topics,
| he has no training and often spouts nonsense which he later may
| decide was a joke.
|
| Second of all, nuking obviously (1) produces far too little
| energy for terraforming, and (2) produces large amounts of dust
| and radioactive fallout. It's also very doubtful that melting
| Mars's poles would do much to help with the habitability of
| Mars - it will still be extremely cold, extremely lacking in
| Oxygen, extremely lacking in atmospheric pressure, and
| extremely radioactive on the surface.
|
| We also don't know how much water is left on Mars after the
| atmosphere was washed away - water may have frozen, but a good
| amount may have simply boiled away in the low pressure and been
| long carried away by the solar winds. Until we know for sure,
| boiling away more water would be extremely irresponsible.
|
| Also, given humanity's current total energy output, there is
| simply no way to terraform Mars. If in the future we will
| discover some way of using orders of magnitude more energy, we
| could visit this, but given current scientific knowledge, any
| energy used to start terraforming Mars is as wasted as trying
| to terraform the Sun.
| whoknowswhat11 wrote:
| I think a lot of the folks who have claimed musk is wrong on
| the science (ie, pro hydrogen, anti nuke etc folks) are
| surprisingly poorly informed.
|
| They have nuclear designs which are 98% fusion. The
| radioactive fallout for these is much more limited.
|
| For example, atomic lake (which was terraformed with nuclear
| bombs), has radiation levels of 9 uSv vs 3 from background
| per week
|
| What's even weirder about the "pro-science" folks - they
| don't seem to understand radiation exposure ranges in space.
| Surface of mars is going to have radiation levels on the
| order of 20 uSv per HOUR - we are talking RADS/year (not mili
| rads).
|
| That said, impactors or nuclear power on the surface are
| likely more feasible.
| magicalist wrote:
| > _They have nuclear designs which are 98% fusion. The
| radioactive fallout for these is much more limited._
|
| > _For example, atomic lake (which was terraformed with
| nuclear bombs), has radiation levels of 9 uSv vs 3 from
| background per week_
|
| It's kind of weird to take an authoritative stance with
| that example. "atomic lake" was from an _underground_
| detonation of a moderate-yield fission device 50 years ago
| and largely just moved dirt around while still sending up
| detectable radioactive waste. OK, you can go _near_ the
| lake now without ill effect but you 've accomplished...what
| exactly?
|
| So scale it up to what is actually needed to vaporize a
| meaningful amount of the ice caps and look at how effective
| that would be at making a dent in the Martian atmosphere
| and the GP has a very good point. It's not a workable idea.
| mensetmanusman wrote:
| ?????
|
| " (2) produces large amounts of dust..."
|
| The purpose would be to produce dust to spark a warming
| feedback loop...
| _Microft wrote:
| We would want something that lets light through but traps
| the heat, meaning that it needs to be intransparent for
| infrared radiation. That's basically greenhouse gases.
| Carbon dioxide and water vapor fit the bill.
| tsimionescu wrote:
| Dust cools, it doesn't help with warming. Also, martian
| dust is extremely erosive, dust storms are already a major
| problem for the prospect of above-surfave structures (such
| as sun panels). Kicking up massive amounts of dust for who
| knows how long into the atmosphere may well backfire.
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(page generated 2021-10-10 23:00 UTC)